The Elephant in the Room

Perhaps someone has mentioned this before and I just haven’t seen it, but in the discussions I’ve seen about how evil assault weapons are the “weapon of choice” of mass murderers, no one seems to be mentioning the obvious.

I’ve seen mention that modern semi-automatic rifles are no different functionally than any other semi-automatic rifle.

I’ve seen mention that there are valid self and home defense purposes for modern rifles.

I’ve seen mention that there are valid hunting purposes for modern rifles.

I’ve seen mention that rifles are rarely used in crimes of any type.

I’ve seen mention that most traditional hunting rifles are more powerful than modern rifles.

But what I haven’t seen is this:

Modern semi-automatic rifles are, by far, the most popular rifles in the US. They are everywhere. Virtually every one at the rifle range has one with them, even if they also have a more traditional pattern rifle as well.

If 80% of the vehicles sold were blue, it would stand to reason that the majority of drunk drivers would “prefer” blue vehicles because they are the easiest to get their hands on just by pure numbers.

If, as a result, legislation were passed banning blue cars, would the incidence of drunk driving go down simply because the preferred color of car for drunk drivers was no longer available?

Silly isn’t it?

So why isn’t silly when we are talking about the cosmetic features of guns rather than the cosmetic features of cars?

National Match AR Range Report

Now that the series of posts on assembly for my National Match AR-15 build project is done, it stands to reason that I need to let everyone patient enough to slog through all those very detailed and meticulous posts know how she shoots.

First a little background. I had heard that new match barrels need to be “broken in” so I did some research on that subject before beginning. It seems that there are as many opinions on that as there are on every other aspect of guns and shooting.

Some recommend using a brush during break-in.
Some recommend not using a brush during break-in.
Some recommend a set number of rounds in a regimen for break-in.
Some recommend shooting only until fouling is reduced.
Most recommend somewhere between 20 and 30 rounds for break-in.
I had one “know it all” type at a local gun range tell me that a minimum of 300 rounds is required for proper barrel break in.
And at least one fairly well known industry professional is on record as saying that “break-in” is unnecessary, does more harm than good and is only recommended by barrel makers to get you to shoot your barrel out faster than you would otherwise.

In summary, after all my research, I still don’t know what the “proper” barrel break-in procedure is or even if there really is one.

Sigh.

Well, I couldn’t find any match ammo to shoot so I was going to have to settle for cheap range ammo to start out with anyway, so I decided to go ahead and do at least some break in.

I went to Camp Allen Weapons range during a time that I thought wouldn’t be too busy (I was right…only one other guy in the bay with me and only for a short time), set up my cleaning station.

Set up my shooting position.

And went to town.

Here are my first five shots, stopping and cleaning between each shot (yes, I used a brush).

I must say, for cheap 55 grain range ammo, shooting one round at a time, getting up, cleaning and then shooting the next round, I couldn’t be happier with that group.

I was using a 6 o’clock hold for the large center diamond, which put me 7 inches low and about 3 inches left.

Unfortunately, I forgot the tools I needed to adjust the FSB. I tried the “bullet tip” trick to adjust the front sight post down to bring the shots up a little, but after a couple of turns, it was obvious that I was going to tear the front sight post up too much if I kept going with that.

After adjusting the front sight post a little, I didn’t know where I was going to be, so I needed to shoot another group to check elevation, but I could at least try to adjust the windage. Let’s see…1MOA at 25 yards is 1/4 inch. I’m shooting 3″ left so I need to move the point of impact 12 MOA right.

One very important aspect of a match rifle is how accurate the click adjustments are on the sights. You don’t get a chance to verify adjustments during a match so you need to know that when you dial in a certain adjustment, that’s what you’re going to get on the Point of impact.

So, with 1/4 MOA sights, a 12 MOA adjustment is 48 clicks. Whew…that’s barely in the adjustment range.

OK…now that I’ve made my first adjustment, it’s time for another 5 shot group. After cleaning between each shot for the first 5 shots, I’m really not seeing any significant copper fouling. A little to be sure, but nothing significant. I think it’s safe to start shooting 5 shots between cleaning.

The second 5 shot group was almost perfectly centered right to left. That tells me that the windage adjustments are accuarate and I can trust my math when making adjustments. That’s great news!

I was still about 26 MOA low though. I wasn’t going to futz with the front post any more without the proper tools, so…I need to move my POI 26 MOA up, that’s 104 clicks.

After cleaning, I shot another 5 shot group: almost exactly where I expected it. Grouped just a little high but almost perfect. OUT STANDING.

I decided to shoot one more group on a clean target to finish off the box of 20 and “for record”. I cleaned one more time, set up…and this is what I ended up with.

Out freaking standing.

I’d say about a 3/4″ group…about 3 MOA. Three out of the 5 cloverleafed.

Using cheap ammo from nothing more than a rudimentary rest and without even having the sights dialed completely in yet.

I’ll take it.

That was the day that I got my gunny body art by the way.

I took her to the Airfield shooting club last weekend and put another 20 rounds downrange and got the FSB windage at least in the ballpark, and I cranked the front sight post down 4 or 5 turns to get the point of impact up a bit. I didn’t take pictures that day because I was just too tired after being out there all day.

Today I went back to the indoor range to verify my FSB adjustments.

Still gonna need some fine tuning after getting the right ammo, but it’s really starting to come together.

here was the last group of 5 (out of another box of 20) that I shot today.

This was with 50 clicks (12.5 MOA) up and the windage dial zeroed.

Looks like I still need to move the FSB about 2 MOA right and the sight post maybe another turn down (Front sight adjustments are opposite of where you want the POI to move, rear sight adjustments are the same direction you want the POI to move).

But the main thing I’m happy about was the groups I was getting tonight.

That one looks to be slightly less than 1/2 an inch.

Call it .45 inches from center to center of the largest spread. I used a box to mark it to make sure the lines were straight down.

At 25 yards, that’s about 1.8 MOA.

I know I’m repeating myself…but…just wow…

Less than 2 MOA accuracy already with crappy ammo that’s really too light for the barrel twist rate from a makeshift rest and without even having the sights all the way dialed in yet.

I think I’ve achieved everything I’d hoped for when I first started contemplating this project.

I’m confident that, with good ammo and from a proper, stable bench rest, I’ll be able to get sub-MOA groups out of this rifle.

I’m officially calling this project a WIN!.

NM Rifle Build Part 10

In Part 1, we introduced the series and talked about tools.
In Part 2, we installed the magazine catch and trigger guard.
In Part 3, we installed and adjusted the Jewell Match trigger.
In Part 4, we installed the safety selector, pistol grip and bolt catch.
in Part 5, we installed the pivot pin, recoil buffer components and buttstock.
In Part 6, we installed the forward assist and the ejection port cover.
In Part 7, we installed the delta ring and barrel.
In Part 8, we installed the free float tube and front sight base.
In Part 9, we installed the handguards, flash hider, bolt carrier group and mated the receivers.

This is the final of the assembly posts. I didn’t specifically try to keep the assembly posts to an even 10, but it is convenient that it worked out that way.

The Front Sight base that came with my DPMS barrel actually had a sight post installed out of the box. It really would have been an acceptable front sight for a NM rifle as it is thinner than the standard A2 Sight, however, the Rock River NM rear sight I bought also came with an actual National match front sight post that I wanted to install.

What?

What’s the difference? I’m glad you asked.

I actually shouldn’t have labeled the one that came on the rifle as “standard” because the standard A2 sight post is a square .070″ post.

The one that came stock in the DPMS sight base was a square post, but significantly smaller than .070″…probably .050″ but I didn’t measure.

The National match post (shown in two different views, side and end-on) is not square, but rectangular. Its also beveled toward the front and is theoretically precision machined to create sharp, distinct edges. The shape is to cut glare and make a nice, clean edged sight picture even at long range.

The only disadvantage to the NM style sight post is that it is designed to be oriented in a specific way. That means when you adjust it, you have to turn it in or out a full turn to keep it oriented correctly, whereas with a square post, you can turn it in quarter turn increments. In other words, the standard front post has four times the adjustment sensitivity of the NM post.

Realistically, though, you don’t adjust the front post for a perfect zero anyway…the front post is only adjusted to get your rear sight in the adjustment range you want…so that isn’t really much of a disadvantage at all.

Installation is the same no matter which type of sight post you choose.

The front sight post assembly consists of three parts (other than the sight base, of course).

The post itself, the detent spring and the detent.

Some match shooters include a set screw with the same diameter and thread pitch as the sight post shaft.

What they do is tap the front sight post hole in the FSB all the way through, and then install the set screw through the bottom. After adjusting the front sight, they tighten the set screw up against it to lock it into place and prevent any movement at all.

I may do that at some point, but I didn’t do it during this assembly process.

The front sight base has two holes in the top. The smaller, front hole is for the detent and the rear, larger, threaded hole is for the sight post.

The detent spring goes into the front hole.

then the detent goes over top of that, with the “nub” pointing up.

Then the post is screwed into the threaded hole.

When the post is screwed down far enough, you’ll have to push the detent down to continue screwing in the sight post.

They make a tool for this, but I don’t have one yet. I never thought I needed it, but after having screwed with the front sight as much as I have lately, I can definitely see that it would make my life easier. I plan to order one from MidwayUSA when I order the sling…maybe today: It’s payday…just gotta pay the bills and see where I stand financially to decide whether I can afford it this time or have to wait for my next check.

It’s hard to see in this picture, but when installed correctly, the National Match front post will be oriented so that the ramped top edge is angled down toward the muzzle end.

It will have to be adjusted to get the zero point of the rear sight where you want it, just remember to adjust the National Match front post in full turns to keep it oriented correctly.

The Rock River Arms National Match rear sight is outwardly almost identical to the standard sight, but there are some differences there as well.

The most obvious difference is that the aperture has a “hood” that is designed to cut down on glare.

The aperture inside the hood is significantly smaller than a standard aperture as well.

The standard A2 sight comes with two apertures, a larger one for close in or low light work and a smaller one for distance. I don’t know the sizes, but I know for sure that they are significantly larger than the .040″ match aperture.

The smaller aperture is not suitable for a defensive or combat rifle because it reduces your field of view to almost zero, but it is great for match shooters because the small aperture increases depth of field (helps keep the target more in focus, even when concentrating on the front sight) and makes it easier to focus clearly on the front sight…as well as just having a smaller area in which to center the front sight post, which can help cut down on tiny errors that can make dramatic differences in impact point at 600 yards.

Another physical difference is the elevation ring. On a standard A2, the elevation knob is actually two parts, the bottom elevation knob, and the top elevation index. They are held together by a set screw. Turning the elevation knob changes the elevation. Loosening the set screw and turning the elevation index, just moves the range index marks to match the sights setting with the effective range that the sight is set at.

The Elevation knob that came with my Rock River National Match sight is a single, solid piece. There are no range markings on the elevation knob at all.

Another obvious feature is that this single elevation knob can be used for 1/2 MOA or 1/4 MOA adjustments, depending on how it’s installed in the rifle. On one side of the knob are detent dimples spaced for 1/2 MOA adjustments.

On the flip side, the dimples are closer together and there are twice as many of them…for 1/4 MOA adjustment clicks.

The final difference is not visible at all unless the windage adjustment knob is removed. The windage adjustments are also set for 1/4 MOA adjustments.

Well made National Match sights tend to be manufactured and calibrated with greater precision than standard sights as well. On National Match sights, one click should be very close to exactly 1/4 MOA (calibrated for a 20″ barrel), whereas standard sights may be in the ballpark, but not necessarily exact.

The RRA rear sight assembly came pre-assembled as much as possible.

The windage knob, ball bearing and spring were already installed, as were the leaf spring and aperture.

The only parts that were loose were the ones that had to be mated with the upper as the sight was installed. Those were the elevation knob, the sight body and elevation detent ball bearings and detent ball bearing springs, the elevation spring, and the rear sight roll pin.

First, drop one of the detent ball bearing springs into the hole in the right front face of the sight base.

It’s a good idea to put a dab of gun grease on top of the spring. That will help hold the ball bearing in place as the sight base is installed.

Then drop the detent ball bearing into the hole on top of the spring and grease.

Next, drop the other detent spring into the lower receiver into the small hole toward the front of the well that the elevation knob goes into.

And put the remaining ball bearing into the hole and on top of the spring.

Next, slip the elevation knob into it’s well in the receiver. It should push the ball bearing down out of the way as it goes in. When properly positioned, the ball bearing will be pressed into one of the elevation adjustment “dimples” on the bottom of the elevation knob, snapping it into place.

Be sure to put the correct side down for the sensitivity of elevation adjustments you want. Since the detent ball is on the bottom, that’s the side of the elevation knob that will determine whether you get 1/2 MOA or 1/4 MOA clicks. In this case I want 1/4 MOA adjustments so I installed the elevation knob with the side up that has the lesser number of dimples.

With the elevation knob installed and the threaded hole of the knob centered in the hole in the reciever, CAREFULLY lower the sight body so that the threaded post goes through the hole in the receiver and mates with the threads of the elevation knob.

Be careful to press the sight body detent ball bearing against the rear flat surface of the carry handle to prevent it from dislodging and falling out of the sight base.

Hopefully, the grease will help hold it in place.

Carefully turn the elevation knob counter-clockwise (when looking at it from the top) to screw the sight base post down into the receiver. You should be able to clearly feel the “clicks” as the elevation knob dimples pass over the detent ball bearing. Be sure to start out slowly. You’ll be pressing the sight body against the spring tension of the sight body detent ball bearing spring, which will be trying to cant the sight body as it goes in. Be careful not to cross-thread the elevation knob as you get it started.

Screw the sight body all the way to the bottom.

At this point, if you haven’t done so already, remove the bolt carrier and charging handle, then flip the receiver upside down.

Inside the receiver, you will be able to see the hole in the bottom of the sight base post. Insert the elevation spring into this hole.

Here’s where things got a little tricky. You have to be able to compress the elevation spring up into the sight body so that the sight pin doesn’t pass through the spring, but under it (over it in this picture because the receiver is upside down).

The problem is that if you press the spring down with something solid like a pin punch, its in the way and you can’t install the pin.

You need something to push the spring down, but won’t interfere with the pin passing through the receiver and sight base post.

They do sell an A2 sight installation tool just for this purpose, but I felt the asking price was a bit high for what it was, I decided to wing it. I made a sight tool out of a popsicle stick.

I used a round jewelers file to file a notch in the top of the popsicle stick large enough for the pin to pass through.

Then I filed the sides down so that it would fit in the hole in the sight base post.

I ended up with a makeshift tool that looked like this.

Not perfectly straight, but close enough for government work.

I used the popsicle stick, aligned fore and aft so that the notch in the top was aligned with the side-to-side pin hole, to catch the edges of the elevation spring and compress it into the sight base.

Once I got the spring down far enough, I used a pin punch to pass over the spring and temporarily hold it in place.

The spring should be captured completely by the pin punch. You don’t want the punch passing through any of the spring loops.

At that point, it was just a matter of driving the sight base pin in and pushing the pin punch out as it went.

And that’s it.

As usual, my explanations were more complicated than the installation procedure.

The last thing to install to make a complete, operational rifle is the magazine.

I purchased two, mil-standard 20 round magazines from MidwayUSA. The magazines are made by C-products, which I’ve heard good things about, but I only bought two for now so I can test them out and make sure they function well before buying more.

I did have one failure to feed and I’ve had the bolt fail to lock back on an empty mag a couple of times, so the jury is still out on these.

Right now, I’m still using cheapo PMC 55 grain ball ammo…which I’ve heard of people having feeding problems with. I’ll know more after I get some good match ammo and try it.

So, over the course of maybe 6 hours over two days, and ten blog posts we went from this:

To this:

Of course, this won’t be the last post about my new National Match AR, I’ve still got a few accessories to add (buttstock weights, possibly handguard weights, and sling), range reports to do, sight adjustments and zeroing, etc…but if all you were here for was the actual assembly process, this is the last of that series.

Click here for first range report

As usual, it took orders of magnitude longer to write the posts documenting the work than it did to actually perform the work…even with staging and taking pictures during the process.

As I mentioned before, my son and I did this assembly (actually, he did most of the work because he wanted the experience…I just took pictures and provided a helping hand from time to time), in about 5 hours on Saturday and about another hour or so on Sunday. We could have done it in half that had we not been worrying about setting up, staging and taking pictures and, now that we’ve done it once and know what we’re doing, could probably come close to cutting that in half again. That’s the beauty of the AR platform: it’s so modular and interchangeable that virtually anyone can assemble, customize and maintain them and the sheer variety of parts and customizations available is staggering.

I’ve already had a couple of comments on posts in this series from people who found them useful and I really appreciate that. Helping people by sharing my experiences is what these posts are all about so, if you find them useful, please let me know in the comments so I’ll be motivated to keep doing them as I experiment, practice and learn more about this gunsmithing stuff.

And, finally, to sum it all up, one more look at the cheesy little video I posted before starting this assembly post series:

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NM Rifle Build Part 9

In Part 1, we introduced the series and talked about tools.
In Part 2, we installed the magazine catch and trigger guard.
In Part 3, we installed and adjusted the Jewell Match trigger.
In Part 4, we installed the safety selector, pistol grip and bolt catch.
in Part 5, we installed the pivot pin, recoil buffer components and buttstock.
In Part 6, we installed the forward assist and the ejection port cover.
In Part 7, we installed the delta ring and barrel.
In Part 8, we installed the free float tube and front sight base.

This time, we’re going to install the handguards and flash hider, assemble and install the bolt carrier group, and mate the upper and lower for the first time.

As usual, click pix to make bigger

The handguards are pretty simple. The only difference between the float tube handguards and standard is that the heat shields are removed, and some of the plastic around the front end is trimmed away to make them fit over the float tube. Other than that they are stock handguards and go on the same way that stock handguards do.

Slip the front tabs of the top handguard into the handguard retainer on the front of the float tube.

Pull back on the delta ring.

Try to slip the back of the handguard into the delta ring.

Grunt.

Pull back on the delta ring HARDER, finally get it to pop in.

They actually make a tool for prying the delta ring back but I always thought $29.99 was a bit steep for a piece of bent thin metal rod so I’ve never considered buying one.

Anyway, repeat with the bottom handguard. Make sure they snap together completely after getting the bottom one into the delta ring. Make sure the delta ring is as far forward as it will go, securing the handguards to the float tube.

The last part of the barrel installation is the flash hider.

There are actually two types of washers that can be used for the flash hider. I chose the peel washer. it is basically a washer made up of thin laminated layers of metal. You can peel off layers to make it exactly the thickness you need.

The other style is the “crush” washer. As its name implies, it crushes as you tighten the flash hider which adjusts the thickness dynamically.

I chose the peel washer becaused it seemed to me that the setup would be more consistent and stable for accuracy. Don’t know if that’s right or not, but seemed that way to me.

What we’re trying to accomplish is to get the flash hider torqued to 15 to 20 pound feet with the ports pointing up and the closed side down.

The first time I put it on, with the full peel washer underneath it, when hand-tight, the ports were canted to the right (as we’re looking at it in the picture). To get the ports indexed properly, the flash hider would have to be turned almost another full rotation. No way that’s going to be right.

The best way I found to peel layers off was with a utility knife. The blade was thin enough to get between the layers easily and with good control, but not so thin that I was worried about it breaking.

Find the thickness that you want to peel away and place the blade there.

Then tap it gently with a small hammer to get it started.

Once the layers have started peeling apart, you can just push the blade through to finish it.

After peeling off a layer and trying it, and peeling off a layer and trying it, I finally ended up with getting it about where I wanted it.

As soon as you think it’s in the right ballpark, try torquing it. If you start to go over 20 pound feet, peel another layer and try it again.

20 pound feet really isn’t much torque so it shouldn’t have to turn far to be torqued correctly.

Conveniently, the AR-15 multi tool has a section made for tightening the flash hider.

Also conveniently, it happens to be oriented so it’s easy to tell when the flash hider is indexed correctly…you turn the tool until it is horizontal and the flash hider is oriented properly.

The hole for the torque wrench is in a strange place in relation to the flash hider wrench part, but as long as you keep the torque wrench at a 90 degree angle with the lever point, it will work fine…or at least it did with my torque wrench. By the way, the extension length for this operation was exactly the same as for the barrel nut torquing: 1.5 inches. That means the correction formula was the same. I actually ended up with an indicated torque of 13 to 18 pound feet to get an actual torque of 15 to 20.

The procedure for torquing is the same as for the barrel nut. Torque to the minimum. If the flash hider still isn’t indexed correctly, set the torque wrench to the maximum and continue turning until the max is reached or the flash hider is indexed correctly, whichever comes first. If the max torque is reached first, you need to take it back off, peel another layer from the peel washer and try again.

The next thing on the list is the Bolt Carrier Group.

The BCG consists of the bolt carrier itself which should include the already installed key and screws. If the key isn’t installed, this is a problem because the screws have to be staked. If you don’t have the staking tool, just be sure to order one with the key already installed.

Also included is the bolt assembly. Also should come pre-assembled, but includes the ejector, ejector spring and ejector pin, the extractor, extractor spring and extractor pin, and the bolt rings.

Next you have the charging handle. This is actually not technically a part of the BCG, but is an integral part of the BCG installation so it’s included here. It consists of the handle, the latch, the latch spring and the latch pin.

Finally, the firing pin, the cam pin and the firing pin retaining pin.

The first thing to do is put the bolt into the bolt carrier, and the first step of that is to make sure the gaps in the bolt rings aren’t aligned.

Sort of like piston rings on an engine piston…the gaps need to be staggered.

The bolt orientation in the carrier is critical as well. The ejector is just a round pin in the face of the bolt. The extractor is a wide hook that extends past the edge of the bolt face.

The extractor hooks on the rim of the cartridge as it is pushed into the chamber. The ejector is compressed under the cartridge base.

After firing, as the bolt moves away from the chamber, the extractor pulls the rim of the empty case, and thereby the rest of the case, to the rear and out of the chamber. Meanwhile, the ejector is pushing against the opposite side of the base of the shell casing under spring tension. As the casing clears the chamber and moves into the ejection port, the ejector pushes the shell casing away from the bolt face, out from under the extractor and out of the ejection port.

If the bolt isn’t in the right way, the ejector and extractor are on the wrong sides. that means that the shell casing will try to eject out the wrong side of the receiver…the side that doesn’t have an ejection port for it to pass through. As you can imagine, this doesn’t work very well and you end up with the empty case jammed in the rifle after your first shot. Basically, it turns your fancy AR into a very expensive single shot rifle.

So, insert the back of the bolt into the front of the carrier and push it in as far as it will go, ensuring that the ejector is to the left, and the extractor is to the right. (opposite in this picture because we’re looking at it from the front).

Next is the cam pin.

The cam pin is what rotates the bolt in the carrier to lock it in the breech when the bolt is closed, and to unlock it so it will open after firing.

There is a large hole that passes through the bolt from top to bottom.

Line that hole up with the elongated hole in the top of the bolt carrier.

Rotate the cam pin so that the hole in it is crosswise to the bolt carrier.

Then insert it into the bolt carrier and bolt through the elongated hole in the carrier.

If you have the cam pin turned the wrong way, it simply won’t go in because the bolt carrier key will be in the way.

Once the cam pin is fully inserted into the bolt and bolt carrier, turn it a quarter turn (either direction…it doesn’t matter).

Now, with the hourglass shaped part to the rear and the pointy end toward the front of the bolt carrier, insert the firing pin through the bolt carrier and bolt from the back.

With the firing pin as far forward as it will go, insert the firing pin retaining pin through the recessed hole in the left side of the bolt carrier and seat it fully.

The “eye” of the firing pin retaining pin should fit down into the recess in the bolt carrier.

OK, now the BCG is together.

The next step is to put the charging handle into the receiver. The charging handle travels along a channel in the top of the receiver. The channel in the receiver has cutouts that the rails in the charging handle will slip through.

The hollow side of the charging handle should be pointing down…it’s up in this picture because the receiver and charging handle are upside down to make them easier to see.

Basically, put the charging handle in the receiver and, while pressing it against the top of the receiver, slowly start pushing it in. When you reach the right spot, the charging handle will slip through the gaps and pop up into the channel it rides in.

Next, make sure the bolt is fully extended from the bolt carrier. The cam pin should be directly under the bolt carrier key and if you pull on the bolt while holding the bolt carrier, it shouldn’t come out any farther.

Now, with bolt face toward the front of the reciever, pull the charging handle out just enough that the bolt carrier key will slip up into the hollow bottom of the charging handle.

Then push the bolt carrier and the charging handle the rest of the way into the receiver together.

If the ejection port cover is closed, it will pop open as the bolt carrier passes it.

When fully inserted, the bolt will rotate and lock into the breech and the charging handle latch willl lock the charging handle into the receiver.

The next step is to mate the upper and lower receivers together for the first time.

One of the idiosyncrasies of the AR platform is that the upper and lower receivers generally don’t fit together tightly. This isn’t normally considered a problem because it doesn’t affect the bore axis/sight plane relationship, and therefore shouldn’t affect accuracy in any significant way.

The movement created by this loose fit can, however, be distracting…which can affect accuracy…and competition shooters usually try to eliminate it. There are several methods at varying expense levels and effectiveness to reduce or eliminate the slop:

Some manufacturers make matched “national match” upper and lower sets that are specifically made to fit tightly together. Another method is to “glass bed” the action where the gap between the receivers is filled with fiberglass reinforced resin. Another common method is special tightening pivot and takedown pins that are deigned to clamp the receivers together and eliiminate the slack. Or you can go the cheap and easy route like I did and just use an accuwedge.

An accuwedge is a rubbery synthetic insert that fits in the lower receiver below and behind the takedown pin.

As the receiver closes, the accuwedge “wedges” itself into the gap.

The upper and lower receivers are connected at two points. First line up the pivot pin holes at the front of the two receivers…

…and press the pivot pin into place. Sometimes this takes some jiggling to get it all lined up. You should feel the detent “snap” the pivot pin in place as it seats fully into the receiver.

With the pivot pin locked in place and the accuwedge positioned at the rear of the lower reciever, close the two receivers together and press tightly to overcome the tension created by the accuwedge.

And then press the takedown pin in to lock it into place just like you did the pivot pin.

And there you have it.

The only things left are the front sight post and rear sight installations.

Click here for part 10

NM Rifle Build Part 8

In Part 1, we introduced the series and talked about tools.
In Part 2, we installed the magazine catch and trigger guard.
In Part 3, we installed and adjusted the Jewell Match trigger.
In Part 4, we installed the safety selector, pistol grip and bolt catch.
in Part 5, we installed the pivot pin, recoil buffer components and buttstock.
In Part 6, we installed the forward assist and the ejection port cover.
In Part 7, we installed the delta ring and barrel.

This time, we’re going to install the free-float tube and front sight base.

In the last post, I mentioned one of the differences between a rifle with a free-float tube and a standard AR…the special barrel nut.

Another difference is that the sling swivel is mounted on the float tube rather than the bottom of the front sight base (FSB). That way the pressure placed on the sling when in a sitting or prone firing position is pulling on the float tube, not on the barrel.

The problem with this is that the standard A2 FSB has an integral sling swivel mount. The mount on the FSB will interfere with the mount on the free-float tube and, so, it’s gotta go.

This is where the dremel tool and carbon cutting wheel come into play.

Of course, you want to be careful and consider that the more attention to detail you give this, the better the end result will look, but it’s a pretty simple procedure.

Clamp the FSB into a vise with padded jaws (or cushion it with rags or pieces of wood).

Cut the sling swivel mounting ears off as close to the bottom of the FSB as you safety can.

You could use a hacksaw for this and I would imagine it would work fine as long as you’re careful. I like the control that the dremel tool gives, but if you don’t have a dremel tool, you probably don’t need to buy one just for this job.

If you need to take some excess off, carefully grind the remaining stubs down until they are almost flat against the bottom of the FSB.

Then use a fine jewelers file to square it up and remove all traces of the sling swivel mount.

You probably can’t really tell in this picture, but the bottom of this FSB is not completely flat. The areas where the sling swivel mount ears were just removed angle down slightly toward the center, where there is a narrow flat spot. I didn’t file the FSB bottom completely flat, but maintained this angled contour in the areas where the sling swivel mount was removed.

I took another step and used a fine stone to remove the filing marks. You could also use emory cloth sand paper at, say, 400 grit or finer to remove the filing marks.

It doesn’t have to be polished or anything, but you want it smooth enough to look “stock”.

Basically, you want to hack the sling swivel mount off without it looking like something’s been hacked off.

Finally, clean the filings off and hit the bare metal you just made with some cold blue to preserve it and match the finish.

With that prep work done, let’s install the float tube.

The free float tube consists of (in addition to the barrel nut), the tube itself, which has the handguard retainer and sling swivel mount permanently attached, and a lock ring.

On a standard barrel, the handguard retainer is just fitted over the barrel and is held on by the front sight base.

That retainer can be discarded as the handguard retainer in this case is mounted directly to the float tube.

On my Rock River free float tube, the sling swivel was not attached out of the box. The tube came with the sling swivel and rivet, but they weren’t installed.

Installation is simply a matter of putting the sling swivel on the mount on the free float tube, sticking the rivet through the holes, and smashing the rivet down with a big punch and hammer.

Next, you may have left the locking ring on the barrel nut while you were installing the barrel.

If so, that’s fine.

If not, thread it onto the barrel nut exterior threads. and screw it on as far as it will go, but don’t tighten it.

Note the round dimple in the locking ring. That will come into play later.

Then slide the float tube over the barrel with the handguard retainer and sling swivel toward the end of the barrel.

Screw it onto the barrel nut.

This is why we needed to remove the sling swivel mount from the FSB before mounting the float tube.

You need to verify the position of the float tube before tightening it down.

Get the float tube positioned about where you think it should go…then slide the FSB onto the barrel and into place to check its position.

I didn’t think to take a picture when doing this, so I took one later, after the gas tube had been installed already.

The float tube should be as close to the FSB as possible, without touching it. If they touch, the tube will interfere with the barrel and defeat the whole purpose of free-floating the barrel. If you make the gap too great, however, the handguard retainer may end up too close to the delta ring and the handguards may not fit.

Also note the sling swivel below the bottom of the FSB. had we not removed the sling swivel mount from the bottom of the FSB, the sight base would not have fit.

Once you’ve verified the position of the free-float tube, take the FSB back off again.

Unscrew the float tube from the barrel nut 5 or 6 turns. Be sure to count, you want to be able to screw it back in the exact same number of turns.

Then put a bit of blue thread locking compound right where the edge of the float tube will be when screwed back in. Put enough on that it will also be under the locking ring once it is tightened against the float tube.

Screw the float tube back in the same number of turns that you screwed it out.

Then, screw the locking ring out until it contacts the float tube.

Before tightening the locking ring, be sure the float tube is as perfectly straight up and down as possible.

the gap that the gas tube will pass through needs to be centered over the gas port in the top of the barrel.

Remember that round dimple in the locking ring that I pointed out before? This is where it becomes important. There is a section of the AR-15 multi-tool that acts as a spanner wrench. It’s a half-moon looking area with a small peg at the end.

Place the half-moon part around the locking ring so that the peg on the tool locks into the dimple on the ring.

While holding the free float tube to keep it from turning, tighten the locking ring against the tube firmly to lock it into place.

And the float tube is done.

The FSB installation on a match rifle is different from a standard AR-15 in two ways. On a standard AR (and even some match rifles, for that matter) the FSB is held on with tapered pins that pass completely through the FSB and barrel. One of the accepted modifications for a match rifle is to drill and tap the taper pin holes in the FSB and use set screws to hold it on. This allows the FSB to be adjusted for windage. On a match rifle, you want your zeros to be as close to the actual zero settings on your sights as possible so that you have the full range of adjustments as well as having known starting points for all adjustments.

This also means that the barrel is slightly different between a standard FSB and an adjustable one. With a standard FSB, the taper pin holes are drilled through the bottom of the barrel. With an adjustable FSB, there are no holes, but generally “flats” are milled into the bottom of the barrel for the FSB set screws to mate with.

That simplifies the initial installation of the FSB, but complicates finalization because you have to adjust it before securing it permanently. for purposes of just getting it onto the rifle, however, it’s pretty straight forward.

The front sight base installation involves the FSB itself, the gas tube and the gas tube roll pin.

The gas tube is the final difference that results from using a free-float tube.

On a standard gas tube (top), the bend in the tube that accounts for difference in height between the gas block and the tube position in the receiver is just aft of half-way. Because the free float tube encloses the barrel, the bend in a gas tube used with a free-float tube must be much farther forward (to the right in this picture) than with a standard installation. The modified gas tube (bottom) was provided with the free-float tube.

One other note about the gas tube. When I first tried it, the gas tube that came with the free float tube wouldn’t fit into the bolt carrier key at all. I thought I had gotten a defective gas tube at first; however, the gas tube is fairly soft metal. What I did was push them together and spin them both against each other. After working them for awhile, this shaped and shaved the gas tube enough that it eventually fit inside the bolt carrier key smoothly. I don’t have the experience to really know but they may have made the gas tube slightly oversized on purpose with the intent of fitting it to the key for a tight seal.

Now for the FSB installation:

I suppose you could mount the FSB to the barrel first and then install the gas tube, but it made more sense to me to pin the gas tube into the FSB first.

Be sure that the gas tube is inserted into the FSB correctly before installing the pin…the end of the gas tube with the holes goes into the FSB. The small hole that passes completely through the tube is the hole for the roll pin. The larger hole that does not pass completely through is the gas port hole and needs to be pointed toward the bottom of the FSB (toward the barrel when the FSB is mounted).

Be sure to get the roll pin hole in the gas tube aligned perfectly with the holes in the FSB. The gas tube is relatively soft and you will crush it if you try to drive the pin in with the holes misaligned.

The gas tube was a tight fit, so after getting it aligned, we didn’t have to worry about it moving.

A tiny little pin punch could be used to help you get them aligned, or a piece of wire, dental pick or other object small enough to pass through the holes might help. We just aligned it by looking through the hole under magnification which worked fine for us.

The gas tube roll pin is very small so we held it with a pair of needle nose pliers and used the nylon mallet to get it started.

Then finished it off with a pin punch.

Next, make sure the channels in the barrel retaining snap ring, weld spring and delta ring are lined up with the notch in the barrel nut.

Then thread the gas tube through the slot in the float tube,

As you press the FSB into place on the barrel, pass the gas tube through the channel in the barrel nut/delta ring assembly and into the upper receiver.

Double check to make sure there is a gap between the rear of the FSB and the float tube, then install and snug down the set screws that secure the FSB to the barrel.

No reason to use thread locking compound on them or torque them down yet…we’ll need to adjust the FSB to zero with the rear sight first.

And that’s it. Starting to look like a rifle.

(Yes, the delta ring is backward in this picture…as I mentioned in the last post, we didn’t realize this mistake until after we tried to install the handguards. I didn’t think to take another picture after correcting it.)

The barrel installation, including free float tube and FSB, were the most difficult part of the whole assembly.

It really was MUCH easier to perform than it was to describe.

Now that I’ve done it once, I think I could do everything described in the last two posts in about 30 minutes tops.

I would say that as long as you invest in the right tools, have any modicum of mechanical ability, and take your time, this is well within the capabilities of your average gunny.

Next time we’ll install the handguards, install the flash hider, assemble and install the bolt carrier group and mate the upper and lower together.

Click here for part 9

NM Rifle Build Part 7

In Part 1, we introduced the series and talked about tools.
In Part 2, we installed the magazine catch and trigger guard.
In Part 3, we installed and adjusted the Jewell Match trigger.
In Part 4, we installed the safety selector, pistol grip and bolt catch.
in Part 5, we installed the pivot pin, recoil buffer components and buttstock.
In Part 6, we installed the forward assist and the ejection port cover.

This time we’re going to install the delta ring assembly and the barrel.

One of the major differences between a National Match rifle and a standard AR-15 is the addition of a free float tube.

Basically, what this entails is attaching a rigid tube from the front of the barrel nut to just behind the front sight. The hand guards and sling swivels are attached to this tube, rather than to the front sight base. The idea is that, when properly using the sling, there is a lot of tension on the front sling swivel. on a standard AR, this tension can cause the barrel to flex. With the barrel “floating” inside this tube, no pressure, either from the hand guards, or from the sling tension, is placed on the barrel, but is taken up by the float tube, allowing the barrel to resonate naturally with each shot, thereby improving accuracy.

You can free float any AR and improve accuracy, but it is most common on match rifles. With match rifles, also, it is important that the external appearance of the rifle remain stock. Free floating the barrel is an accepted modification, but you have to use standard handguards.

As usual, click all pix to make bigger

The free float tube comes with a special barrel nut that is different than a standard nut.

The standard barrel nut is only threaded on the inside where it mates with the upper receiver and does not extend past the gear-like “head”.

The barrel nut used with a float tube, on the other hand, looks the same up to the “head” but extends past that area and is threaded on the outside. Those extended exterior threads are what the float tube screws onto.

Notice the groove machined into the unthreaded part of the barrel nut on both the standard style, and the free float tube style barrel nut.

The barrel installation involves the special barrel nut, the barrel and the three components of the delta ring assembly: delta ring, weld spring and snap ring.

The barrel installation itself is identical whether using a float tube or not, the only difference in this part of the assembly is which type of barrel nut is used.

First, the barrel nut should be placed on the bench with the exterior threaded part (or the “head” with a standard barrel nut) down.

Place the delta ring over the unthreaded part of the barrel nut. The slope of the delta ring should be sloping in toward the bottom.

We actually installed the delta ring backward initially. I thought it looked funny, but I couldn’t quite pinpoint why. Everything fit fine (although it was harder than it should have been to torque the barrel nut with the delta ring in the way) and we didn’t realize what the problem was until we tried to install the handguards…which wouldn’t fit.

This is what it looks like with the delta ring installed backward.

It shouldn’t look like this. If you can see the weld spring, you did it wrong.

Next, the weld spring goes over the barrel nut and should fit down inside the delta ring.

Then, using the snap ring pliers, install the snap ring into the groove machined toward the edge of the barrel nut.

You’ll have to compress the weld spring a little to get the snap ring on, but it isn’t very hard if you use a properly sized set of snap ring pliers.

You can probably do it without the pliers, but they make it much easier.

With the upper receiver in the action block and the action block securely fastened in the vise, install the barrel onto the lower receiver.

The indexing pin in the barrel extension should seat fully into the notch in the upper receiver threads.

Next, grease the upper receiver and barrel nut threads with a good molybdenum disulfide grease.

Popsicle sticks can really come in handy…and they’re cheap. I bought a bag of 250 for a couple of bucks a few years ago and still have probably half the bag left.

There are as many opinions about what kind of grease to use as there are AR-15′s in the world. As a Honda motorcycle owner, I just happened to have a very good Moly-B (that’s what we used to call molybdenum disulfide based grease in the Navy) that’s used on the drive shaft splines of my bike. That’s what I used.

The only real dire warning I’ve found about the grease selection is to not use grease with graphite in it because graphite can act as an electrolyte and increase the chances of dissimilar metal corrosion due to the barrel nut being steel and the receiver being aluminum.

I have no idea how valid that concern is but it was something I ran across when researching this project.

After applying a little grease with the popsicle stick, I used a rag to even it out and remove excess. You don’t need a lot, just enough to put a light coat on the threads.

The purpose of the grease is to act as an anti-seize compound and to prevent galling of the receiver threads while tightening the steel barrel nut.

Next, slide the barrel nut over the barrel with the external threads toward the end of the barrel and the interior threads toward the receiver.

Thread the barrel nut onto the receiver threads and hand tighten.

The next step is where the AR-15 multi-tool was critical.

There is a square hole in the center of the multi-tool just behind the barrel nut part of the tool. That hole is designed for a 1/2 inch drive torque wrench to fit.

The barrel nut should be tightened to a minimum of 30 pound feet and a maximum of 80 pound feet.

Now…I probably went a little overboard, but knowing that using an extension alters the actual torque from the setting on the wrench, I used the magic formula to make sure the torque setting was accurate:

Torque setting on wrench (Ts) = Actual torque desired (Td) times lever length of the torque wrench (Lw) divided by lever length of torque wrench (Lw) plus length of the extension(Le).

Ts = Td(Lw/(Lw+Le))

Since we’re using pound feet, all measurements have to be in feet.

The lever length of the torque wrench is from the center of the grip to the center of the drive. Mine is 15 inches or 1.25 feet. The length of the extension is from the center of the drive, to the center of the torque wrench attachment point…1.5 inches or .125 feet. With long extensions, you have to account for the angle that the wrench is attached to the extension as well, but for one this short, as long as the angle isn’t too great, it won’t make much difference.

So: Torque desired (Td) = 30 pound feet
Lever length of torque wrench (Lw) = 1.25 feet
Lever length of extension (Le) = .125 feet

T(s) = 30(1.25/(1.25+.125))
T(s) = 30(1.25/1.375)
T(s) = 30(.909)
T(s) = 27.27 pound feet

So, I set the torque wrench to 27 pound feet rather than 30. Not a huge difference, as I suspected, but better safe than sorry right?

After the nut is tightened to the minimum torque, the next step is to see if you have a notch in the barrel nut “head” aligned with the gas tube channel.

You’ll probably have to move the snap ring, the weld spring and the delta ring in relationship to each other to line up all three of the channels with the barrel nut.

A dental pick or “L” shaped allen wrench works well for this.

A good way to check the alignment is to stick the gas tube through the channel and see where it points.

If the tube doesn’t point straight down the barrel centerline, then you’ll need to turn the barrel nut more to get it lined up.

I had an extra gas tube to use because the float tube came with its own gas tube. I just left the tube in place while turning the barrel nut so I’d know as soon as it lined up. I wouldn’t do this with the gas tube I’m going to install because I’d be afraid of it binding and being bent or crushed. If you don’t have a spare gas tube, a piece of thin dowel rod or something like that would work just fine.

The maximum torque is 80 pound feet. Using the formula to adjust for the extension, I came up with a torque setting of 73 pound feet. Set the torque wrench to the maximum and then tighten the nut until the tube is aligned with the barrel or the maximum torque is reached, whichever comes first.

If you reach the max and haven’t gotten the gas tube aligned, stop, loosen and try again. Torque to 30, then try to align the gas tube notch without over torquing. If you still can’t get it, I’d say having it a pound or two under torqued would be better than over torquing it. I’d be very leery of damaging those aluminum threads on the receiver.

If you do have to under torque the barrel nut, I’d check it regularly to be sure it’s not backing out and crushing the gas tube.

After the barrel nut is torqued, the barrel installation is complete.

I did hit the barrel nut with some cold blue after torquing. The multi-tool had scraped the finish off of some of the crowns of the nut and I didn’t want to leave them bare.

No progress picture for you this time…I forgot to take one until after we had the float tube on.

I obviously need more practice at this stuff.

I was originally going to include the float tube installation in this post, but it was getting too long so you’ll just have to be patient.

Next time we’ll install the free float tube and the front sight base.

Click here for part 8

NM Rifle Build Part 6

In Part 1, we introduced the series and talked about tools.
In Part 2, we installed the magazine catch and trigger guard.
In Part 3, we installed and adjusted the Jewell Match trigger.
In Part 4, we installed the safety selector, pistol grip and bolt catch.
in Part 5, we installed the pivot pin, recoil buffer components and buttstock.

This time, we’re going to start on the upper receiver by installing the forward assist assembly and the ejection port cover.

The forward assist assembly is pretty straightforward. It consists of the assembly itself, a large spring and a roll pin.

The forward assist goes into the large, angled hole on the right side of the upper receiver.

On the “post” part of the assist assembly, there is a flat area. that area is where the pin engages and holds the forward assist in. As the assembly is installed, that flat area needs to be in toward the center of the receiver.

The spring slips over the “post” part of the assembly.

Then insert the assembly into the hole, compressing the spring so that the flat on the assembly’s “post” area will line up with the pin hole.

Then drive in the roll pin.

Pretty simple.

The ejection port cover isn’t much more difficult to install.

It consists of the cover and latch assembly, the hinge pin, the spring, and a TEENY TINY retaining ring (It would be VERY easy to lose this so be careful with it. When I first pulled the components out of the shipping bag, the retaining ring was stuck to the ejection port cover itself and I thought it was missing until I spotted it clinging to the preservative oil coating).

We were, for some strange reason, thinking that this installation might damage the finish (silly us…not much chance of that), so we taped the side of the receiver forward and aft of the ejection port. That was completely unnecessary, but better safe than sorry, right?

First, clip the retaining ring into the groove close to the end of the ejection port cover pin. It went on very easily, but, again, be very careful, if you put too much pressure on it and it pops out of your hands, you will probably never see it again.

As I’ve explained in the past, this is one reason for the towel that I always put down on the work bench. If you drop (or launch) small parts while trying to install them, they have less tendency to bounce when they hit the towel, they tend to stop right where they hit and generally are easier to find.

Then put the spring in place on the ejection port cover itself and position it on the receiver.

Make sure the latch on the cover will be in toward the receiver when the cover is closed.

The short arm of the spring goes against the receiver and the long arm goes into the crease in the ejection port cover.

The easiest way I found to do this was to put the long arm in place on the cover door and stick the short arm in the receiver through the ejection port, then drag the cover down into position between the mounting ears, catching the short arm of the spring on the edge of the receiver as it goes. I had to put my finger across the spring to keep it from bending and popping out of position.

While holding the cover and spring in place, from the front of the receiver and with the retaining ring end of the ejection port cover pin toward the front of the receiver, slide the pin in, through the cover and the center of the spring.

It sounds more complicated than it is. It really was very easy to do.

The retaining ring keeps the pin from sliding to the rear and out. After it’s installed, the delta ring keeps the pin from sliding forward and out.

The spring tension was plenty to keep the pin in place until the barrel and delta ring were installed.

And that’s where we’re at.

Next time, we install the delta ring and the barrel.

Click here for part 7

NM Rifle Build Part 5

In Part 1, we introduced the series and talked about tools.
In Part 2, we installed the magazine catch and trigger guard.
In Part 3, we installed and adjusted the Jewell Match trigger.
In Part 4, we installed the safety selector, pistol grip and bolt catch.

This time we’re going to finish the lower up by installing the pivot pin, takedown pin, buffer components and buttstock assembly.

The pivot pin is the longer of the two similar pins that secure the upper receiver to the lower receiver after the rifle is complete.

The pivot pin and takedown pin detents and detent springs are identical.

First, drop the detent spring down into the hole on the front face of the lower receiver. The hole is located inside a visible ridge on the upper right side of the magazine well.

Next, the detent goes in on top of the spring. There is no flat on this detent like there is on the selector detent…both ends of the pivot and takedown pin detents are slightly pointed.

The spring is actually longer than the hole so the detent will have to be pressed down into the hole.

For the pivot pin to go in, the detent has to be pressed completely into the hole. Be careful not to slip or you’ll fire that little detent across your work area and probably won’t find it again.

There is a special tool for depressing the detent while installing the pivot pin but I don’t use it. I’ve found that a small piece of flat metal about 1/2 inch in width, and about .020 inches in thickness works very well for this task. Conveniently, a set of automotive feeler gauges provided a piece of flat metal that perfectly fit the bill. You may note that I forgot to include the feeler gauges in my list of tools and picture in the first post. I knew I’d forget something. There are probably any number of other flat, stiff items around your house that would work just as well if you don’t have a set of feeler gauges.

While compressing the detent into the hole by holding the feeler gauge flat against the top of the receiver face, slip the pivot pin into the holes of the receiver. The pivot pin goes in from the right side, with the flat part of the pivot pin head (and the groove machined into the length of the pivot pin) toward the rear of the receiver (and the detent).

Once you get the pin in as far as it will go, pull the feeler gauge out from under the pin. The detent will snap into the groove in the pivot pin, locking it into the receiver. Push the pivot pin the rest of the way in.

You should be able to feel the pivot pin “snap” into place when it is pushed all the way in, but should be able to snap it back out by pushing it with your fingertip from the left side of the receiver. After it snaps free, you should be able to extend it fully and feel it “snap” into place again when it reaches its full extension. It should NOT pull from the receiver.

When you are pulling it out for the first time, be sure to cup your hand over the face of the receiver in case there’s something wrong. If the pin pulls completely out, the detent and detent spring will rapidly depart the area.

There are actually three separate subassemblies involved with the buttstock:

The takedown pin components: takedown pin, takedown pin detent and detent spring

The buttstock: buttstock assembly, stepped spacer, and lower receiver extension self-locking screw

And the recoil buffer: buffer assembly, buffer tube, recoil spring, buffer retainer and buffer retainer spring.

First, start screwing the threaded end of the buffer tube into the lower receiver.

Just get it started, don’t screw it more than a couple of turns yet.

Next, drop the buffer retainer spring into the hole in the bottom part of the threaded area that the buffer tube screws into.

Then drop the buffer retainer in over the retainer spring.

Press down on the buffer retainer and then finish screwing in the buffer tube. When properly installed, the buffer tube should be screwed in just enough to catch the “lip” of the retainer. The “pin” part of the retainer should still be sticking up and the retainer should be able to move up and down with no binding.

The recoil spring is then inserted into the buffer tube.

And then the buffer assembly goes into the spring, and into the buffer tube.

Press down on the buffer retainer to get the buffer assembly past it.

After the buffer assembly is fully seated in the buffer tube, release the retainer, allowing it to “trap” the buffer assembly inside the tube.

Next, insert the takedown pin into the hole in the right rear of the receiver.

The flat part of the head on the pin and the groove machined into the length of the pin should be toward the rear of the receiver.

The hole for the takedown pin and takedown pin detent is in the rear face of the reciever.

With the takedown pin fully inserted, drop the detent into the hole.

Then drop the detent spring into the hole on top of the detent.

While keeping the rear of the receiver up to prevent the detent and spring from falling out, place the stepped spacer on the rear of the buffer tube. The smaller “step” should be pointing up…away from the buffer tube.

Then carefully slide the buttstock assembly over the stepped spacer and down onto the buffer tube.

As the buttstock assembly approaches the receiver, be sure that it pushes the takedown pin detent spring straight into the hole in the receiver and doesn’t bend it over and crush it.

Finally, install the lower receiver extension self-locking screw through the hole in the top of the buttplate and screw it into the rear of the buffer tube.

The screwdriver looking end of the AR-15 multi-tool can be used to tighten this screw, but I like the control of a large screwdriver better for this task.

If you use a screwdriver, be sure to use one with a large enough blade that it fits the slot in the screwhead tightly so that you don’t damage the screw. This screw should be tightened firmly both because it is the only attachment point of the buttstock to the receiver, and to lock the buffer tube in place.

Check the operation of the takedown pin at this time. It should operate just like the pivot pin: “snap” into it’s fully closed and fully open positions and you should not be able to pull it completely out of the receiver.

So…after 5 posts, we’ve gotten the lower receiver completely assembled.

Next time, we’ll install the ejection port cover and forward assist onto the upper receiver.

Click here for part 6

NM AR Rifle Build Part 4

In Part 1, we introduced the series and talked about tools.
In Part 2, we installed the magazine catch and trigger guard.
In Part 3, we installed and adjusted the Jewell Match trigger.

This time, we’re going to install the safety selector, pistol grip and bolt catch.

The pistol grip has to be installed at the same time as the safety selector because the pistol grip is what holds the selector detent and detent spring in place.

The detent is the only thing that holds the selector in place, so without the pistol grip, the detent and spring would fall out and, without them, the safety Selector would fall out.

The first step to installing the safety is to cock the hammer.

Astute observers may note that the hammer is not cocked in this picture. I took the picture as my son was trying to get the safety to drop in. It took us a few minutes to figure out why it wouldn’t go. When we did figure it out, I didn’t think to re-take the picture so you’re stuck with a picture of how “n0t” to do it.

Anyway, with the hammer cocked, the safety selector should drop in from the left side of the receiver.

This would be a good time to check the operation of the Safety Selector. I had no problems with mine, but you may have to readjust the trigger or even do some fitting on the safety to ensure that it operates correctly.

With the safety selector inserted fully into the receiver, turn the receiver upside down.

There is a small hole in the right side of the receiver next to the pistol grip mounting area. The detent goes into this hole with the pointy end toward the safety selector and the flat end visible.

The selector detent spring goes into a hole in the right side of the pistol grip.

With the detent in place in the receiver, and the spring in the well in the pistol grip, install the grip onto the receiver. Be careful to mate the end of the spring with the flat of the selector detent as the grip goes into place.

Put the lock washer on the pistol grip screw, then install the screw through the bottom of the pistol grip. My grip screw was a straight slot, but different makers may use different screw types. The picture notwithstanding, It is actually easier to get the screw in the hole inside the grip by placing the screw on top of the screwdriver, and then lowering the receiver and grip onto it. Dropping it into the grip and hoping it finds the hole can work…but generally not on the first try…or second…or third…or tenth…

The bolt catch assembly consists of four components. The catch itself, the plunger, the plunger spring and the bolt catch pin.

Installing the bolt catch is where the packing tape comes in. Some people us duct tape or masking tape but I don’t like either of those options because the glue is too hard to get off later. Painters tape would probably work, but I’ve had very good luck with clear packing tape. it protects the finish, but comes off easily afterward.

Installing the bolt catch requires you to drive in a roll pin along the length of the receiver. If you don’t protect the finish, you could damage it with the pin punch or hammer as you are driving the pin in.

Basically, you want to tape the left side of the receiver, both above and below the bolt catch mounting ears, but be sure not to block access to the well that the bolt catch goes into or the pin holes in the mounting ears. I usually use a double layer of tape to be sure it’s thick enough to protect adequately.

After the receiver is taped, drop the bolt catch plunger spring into the hole below the bolt catch mounting ears.

Then the plunger goes into the same hole over the spring.

Next the bolt catch goes on with the catch at the top of the receiver and the button outside and sticking up above the top of the receiver.

To seat it completely, you’ll have to press it in against the spring tension of the plunger and plunger spring.

Then, from the rear of the receiver, slip a pin punch through the pin holes of the mounting ears and the bolt catch to hold them in position and keep the holes aligned as the pin is going in.

This is the point where, if you don’t have an extra set of hands as my son and I did this time, a hobby vise or lower action block comes in handy.

With the receiver on end, the objective is to drive in the roll pin which will push out the pin punch.

I generally get the roll pin started first by holding it in place with the small needle nose pliers and tapping it with a very small hammer or nylon mallet.

After it’s started, switch to a long pin punch to finish driving it in. I did this by myself when I assembled the first AR (Barack) last spring so it is possible to do it as a one person operation…but it sure is easier when there are four hands involved.

Once the pin is fully seated, the tape can be removed from the receiver.

And here’s where we stand.

Next time we’ll finish assembling the lower by installing the pivot pin, takedown pin, buffer components and buttstock.

Click here for part 5

NM AR Rifle Build Part 3

In Part 1, we introduced the series and talked about tools.
In Part 2, we installed the magazine catch and trigger guard.

This time, we’re going to install the Jewell match grade, 2 stage adjustable trigger and go over the adjustment procedure.

The Jewell is pretty plainly not the absolute best trigger out there; and I have read some reviews complaining about them being too hard to adjust or not having the longevity that they should. As far as the first complaint, I’d say they either installed it wrong or were not adjusting it properly. Only time will tell whether the second complaint is accurate or not. I will say that, now that I’ve gotten mine installed, I’m very happy with it so far.

One of the biggest complaints about the Jewell trigger is that the installation instructions suck. That one I can wholeheartedly agree with. Hopefully, this post will come in handy for those intrepid souls who scour the internets for information that will make their lives easier.

As usual, click all pix to make bigger

The Jewell trigger assembly is very different from the standard trigger and hammer assembly.

Fortunately, the hammer spring is already installed in on the hammer out of the box and the trigger and disconnector assembly are already assembled.

This simplifies things considerably.

BTW: The nammer and trigger pins do not come with the trigger. You have to buy them separately. They do make both small pin and large pin versions of the trigger so you can get what you need for your lower.

The first step is to figure out how the trigger return spring fits on the trigger.

It goes on the left side of the trigger.

The spring has a bent leg and a straight leg.

The bent leg goes toward the trigger and the tip should be pointing up. There is a small “peg” on the left side of the trigger that this bent leg should catch on when properly installed.

Place the trigger into the lower receiver with the spring in this position.

It may not stay perfectly aligned because it’s a pretty loose fit. That’s OK, as long as the loop is positioned so the pin will go through it, you’re OK.

Next, while holding the trigger and spring to keep them aligned with the trigger pin holes, insert the trigger pin. FROM THE RIGHT SIDE (I’m yelling because this is important) and with the offset groove to the right.

Don’t put the pin in all the way yet, just enough to keep the trigger from falling out.

Now, slide the first stage adjustment plate in between the trigger return spring and the side of the receiver. If you pushed the pin in too far in the previous step, you may have to pull it back out a little to get the plate to go in.

The plate should be installed with the “teeth” pointing inward toward the trigger and the flat edge down toward the bottom of the receiver.

Line the plate up with the trigger pin hole, be sure that loop in the spring is still aligned with the trigger pin, and finish pushing the trigger pin the rest of the way in.

Next, the straight arm of the trigger return spring has to be brought up to engage the teeth in the first state adjustment plate. This is where the wire tool that came with the trigger came in handy.

One end of the wire is hooked. Use that hook to snag the straight arm of the trigger return spring and pull it up until it engages the adjustment plate. Which tooth it engages isn’t important at this point, as long as the spring is engaged in the adjustment plate teeth.

As you put tension on the spring, if it’s installed correctly, the bent arm of the spring should engage the peg on the left side of the trigger assembly.

Mine hooked right in. I’m sure if it doesn’t, you could just jiggle or move it around a bit until it pops into place.

AFTER the straight arm of the trigger return spring is engaged in the adjustment plate teeth, it’s time to install the hammer. If you forget and put the hammer in first, you’ll have to take it back out because the trigger return spring won’t fit past it once it’s installed.

The hammer’s pretty straightforward.

There is a cylindrical “roller” type bearing on the front part of the hammer spring. That roller goes against the front of the receiver.

As the hammer is pushed down into position, pry it back against the spring tension and lever the bottom in toward the front of the receiver.

Once you get the pin hole in the hammer aligned with the holes in the receiver, you can insert the hammer pin, again with the offset groove to the right.

It might make it easier to use a pin punch to line everything up and then push the pin punch out with the hammer pin.

Next, the hammer and trigger pin retainer goes in. On a standard trigger assembly, the hammer and hammer spring engage the grooves in the hammer and trigger pins to lock them in place. The Jewell trigger, because of the difference in design, doesn’t have that locking mechanism built in.

That is the purpose of the pin retainer.

From the right side of the receiver, gently push the trigger pin until it clears the side of the receiver. You just need it to clear the side of the receiver, don’t push it completely out.

Slip the loop end of the pin retainer between the right side of the trigger and the wall of the receiver.

the straight arm of the pin retainer should be pointing forward and down toward the hammer pin.

Once the loop is in position, seat the trigger pin fully back into place.

For the next step, the other tool included with the trigger comes in handy.

Use the wedge end of the tool to gently pry the hammer spring away from the right side of the receiver.

You’re trying to create a gap large enough for the pin retainer to slip through.

Once you have a gap between the hammer spring and receiver wall, use the notch in the trigger tool to push in and down on free end of the pin retainer.

Slip the arm of the pin retainer between the hammer spring and receiver wall, and so that the retainer is to the rear of the hammer pin.

Press it down until the half-loop in the pin retainer snaps around the hammer pin.

Once the pin retainer is in place, it should be under tension between the two pins.. The tension should force the two wire loops into the grooves in the hammer and trigger pins and lock them into place.

I pushed the pins back and forth slightly a few times while pressing down on the visible part of the the pin retainer to ensure that it locked into the grooves.

That’s it for installation. That wasn’t so bad now was it? Now for adjustment.

***IMPORTANT NOTE*** it is not good for the lower receiver to dry fire without the upper installed. Dry firing without the upper causes the hammer to impact the aluminum front of the trigger well in the receiver. Since aluminum is a relatively soft metal, this can cause damage to the receiver.

All is not lost, however. What I do is stick a popsicle stick between the front of the hammer and the rear wall of the receiver. When the hammer falls, it hits the popsicle stick versus the aluminum receiver and prevents damage to the receiver wall. This destroys the popsicle stick within about three or four dry fires, but popsicle sticks are significantly less expensive than lower receivers and are not regulated by the ATF (yet). [/NOTE]

There are four adjustment points for this trigger. The first is the first stage trigger pull (aka takeup) that is adjusted by the tension of the trigger return spring. This can be changed by moving the straight arm of the trigger return spring into different teeth of the first stage adjustment plate.

Both of the trigger tools were useful for this adjustment. When the trigger return spring is toward the front (least tension) end of the adjustment plate, the hooked end on the wire tool seemed to work best for pulling the arm back into the higher tension ranges of the adjustment plate.

But after the half-way point, it seemed easier to use the notched end of the other trigger tool to push the spring into the higher range of the adjustment plate’s positions.

I was very impressed with the range of adjustment options that this setup gave for the first stage trigger pull tension.

The other three adjustments are made by turning allen head set screws on the trigger assembly itself.

The first of these adjustments to make is the sear engagement adjustment.

This adjusts how far the trigger moves during the second stage of the trigger pull…after the trigger makes contact with the sear, how far it moves before the sear releases the hammer.

This movement is also called “creep”. The more creep there is, the less “crisp” the trigger is. With too much creep, the trigger can feel mushy or gritty as it releases.

Too little creep is a problem as well though. If there isn’t enough sear engagement, the hammer may fail to lock back after firing and “follow” the bolt down as it closes. At best, this means that the hammer won’t be cocked between shots and you’ll have to manually operate the bolt to cock the hammer. At worst, this condition can cause uncontrolled full auto fire. Not only is uncontrolled full auto bad for your scores in competition, but it can result in an out of battery cartridge detonation which is a very convenient method of turning your upper receiver into a hand grenade.

One other point about adjusting the sear engagement. This screw cannot be accessed with the hammer cocked. That means you should go slowly and make very small adjustments. If you get overzealous, you could adjust it to the point that the hammer won’t release at all. This is bad because, as I said before, you can’t reach the screw with the hammer cocked. If the hammer is cocked and won’t release, and you can’t reach the adjustment screw…there is only one way to adjust it: take the hammer and trigger pins out, remove the whole trigger assembly to release the hammer, adjust some of the sear engagement out, and then reassemble the whole thing.

I’m sure you can imagine how I figured that one out.

At any rate: The way I adjusted the sear engagement is, I basically adjusted it down until I had a hair trigger. Then I put maybe an eighth of a turn of engagement back in to be sure the engagement was sufficient to be safe. After firing my first 20 rounds through it tonight, that method seems to have worked well: no failures of any kind. So far so good.

The next adjustment is the second stage pull.

This is what determines how much pressure is required from the end of the first stage “takeup” until the trigger releases.

This is adjsuted with the larger allen screw on the rear of the trigger assembly.

You can adjust this down to the point that there is no appreciable second stage…the pull is smooth all the way until the hammer releases…or up so that significant force is required to release the hammer.

According to the instructions, Jewell recommends adjusting the first stage pull to 3 1/2 pounds, and then the second stage to 1 pound, for a DCM legal 4 1/2 pounds of pull.

While experimenting and dry firing, that didn’t feel “right” to me. The takeup felt too tight and the second stage release didn’t feel sufficient to give me a distinct release point. I decided to lower the first stage and increase the second stage a little. By my rinky-dink pull gauge, I read a first stage of 2 1/2 pounds and a release at 4 1/2 pounds for a second stage of 2 pounds.

I have to say that, after shooting it tonight, I think I was wrong. I’m going to adjust it closer to Jewell’s recommendation. What felt good when dry firing, didn’t feel so good when actually shooting. The first stage felt OK, but the release was too tight. It was crisp and clean, but just too heavy. I’m going to reduce the second stage, but to keep it within the DCM legal 4 1/2 pound range, I’m going to have to increase the first stage by an equal amount. That’s going to put me right around where Jewell recommended to begin with: 3 1/2 pound first stage, 1 pound second stage.

I guess they actually knew what they were talking about.

The final adjustment is overtravel.

This controls how far the trigger continues to the rear after the hammer releases.

It is adjusted with the small allen screw on the front right of the trigger assembly.

Overtravel (arguably) isn’t quite as critical to a good trigger pull as the sear engagement and pull weights, but it does make a difference in the overall feel of the trigger. When the trigger stops moving to the rear just as the hammer releases, it just feels more precise and actually makes the second stage pull weight feel less than it actually is. In other words, you can probably get away with a long overtravel distance, but the entire trigger experience is improved by reducing it.

The bst way to adjust the overtravel is to turn the screw in until the hammer simply won’t release at all. You can do that with this adjustment because you can still get to the screw with the hammer cocked. Once you’ve got it down to where the hammer won’t release, back the screw out a about a quarter turn and pull the trigger. If the hammer still doesn’t release, back the screw out another quarter turn and try it again. Repeat just until the hammer releases.

That’s the minimum overtravel you can have and still release the hammer.

That’s it. The trigger is installed and adjusted, so here’s where we’re at.

Next time well install the Safety Selector and Pistol Grip, and the Bolt Catch.

Click here for part 4