AR-308 Part 5

Previous posts in the series:
Part 1
Part 2
Part 3
Part 4

OK…the rifle is together. If I’d bought one off the shelf, that’s pretty much what I would have gotten. There are still a few odds and ends to add, like a magazine, a scope, a bipod, etc…but those wouldn’t have come with an off the shelf rifle and I’d still have to buy them anyway…so for an apples to apples comparison, what’s the tally so far?

$565. Excellent.

But we still have some loose ends to tie up. There are two components that, although not technically necessary for shooting the rifle, they really make it work better: A magazine, and some sort of sighting system.

I ordered a 10 round Magpul LR-308 Pmag from Midway USA for $18.

The sighting system was a little more complicated. I knew I wanted a scope because I want this rifle to be a tack driver at range. I’d love to be able to shoot it well at 500 or 1000 yards so I wanted something that would work for long range…variable power and a high zoom level.

Another thing I like is Mil-dot reticles. I like the fact that a mil-dot reticle can be used to estimate range. The down-side of that with a variable power scope, however, is that if the reticle is in the second focal plane, you have to adjust your calculations by the zoom level of the scope at the time…that really complicates the math. With a first focal plane scope, the reticle zooms along with the background, so the perspective stays the same, regardless of the zoom level of the scope. That makes the math (relatively) easy.

Adjustable Objective is a must for me. I don’t like having to worry about compensating for parallax. And a large diameter objective means more light, better view.

But, I didn’t want to spend $1000 or $2000 either. After reading review after review and finding scopes that were close, but was missing one or another feature I was looking for, I ended up finding a Vector Optics Counterpunch at Optics Planet for $200. Vector Optics gets mixed reviews, but, again, for the price, I figured it would do for now and I can upgrade in a year or so if needed.

Finally, just a couple of optional accoutrements I ordered from Amazon.

Bipod $38
2 point Sling $10
GrovTec QD bases $8 (needed to add QD sling swivels to the Luth-AR stock)
M-loc QD sling base $12
QD Sling Swivels $9

And that completed the build. I now have a fully operational rifle, customized exactly how I wanted it.

Total cost: $852

A little over my original budget, but very good nonetheless.

I have to admit that I did splurge and break the bank a bit. On the first range trip, the cheap-o FCG I had in there left, um, a lot to be desired. Very gritty, heavy pull and the pins walked loose, causing the rifle to malfunction. This won’t do at all. I could clean up the trigger, reduce the pull and make it smoother, but I’d still have to worry about the pins walking.

Considering I’m hoping this rifle will be a tack driver, I decided that skimping on the trigger isn’t a good idea. I decided I wanted a good match style 2 stage trigger. I was going to buy a Jewell like I had on my National Match AR-15, but alas, they don’t appear to make them anymore.

That’s a right shame…I loved that trigger. Completely adjustable and smooth as glass. I was really disappointed when I checked their web site and they don’t list them any more.

I settled on a Geissele G2S. Not adjustable, but pre-set for a 2.5lb takeup and a 2lb release for a total pull weight of 4.5 lbs. I prefer more on the takeup and less on the release, but that’s the closest I could get to what I want. I had my Jewell adjusted for a 4lb takeup and a 1lb release to meet the minimum 5lb pull needed for matches.

I could have gone cheaper…Rock River makes a similar 2 stage match trigger for half the price, but from what I’ve heard, it’s half the quality as well. The Geissele was $165 at Optics Planet, but after shooting it, I’d have to say, worth the price.

So I ended up at a little over $1000 all in. Sigh. It’s only money, I can make more…

Anyway…I took it back to the range with the upgraded trigger today. It ran like a clock, everything was perfect.

So, what’s the verdict?

I think it’ll do.

100 yards on a standard sight-in target with 1″ squares. That’s a 3 shot group right at 1″.

This was from the bipod with cheap Remington Core-Lokt 150 grain ammo. I got 1″ groups or close to it consistently after dialing the scope in with cheap ammo and a not entirely stable rest. I really can’t wait to see what it’ll do with some match grade ammo. I’m pretty confident that it will do sub-moa.

Mission accomplished. The only question is: how long will the cheap scope hold up? Time will tell.

Final Post in the series.


AR-308 Part 4

Previous posts in the series:
Part 1
Part 2
Part 3

So, we’ve got all the parts for the basic rifle, now we just need to put it together.

I’m not going to go through the whole assembly process as it’s no different than the standard AR-15 assembly I’ve covered that at least twice here on this blog; also, you can find the process everywhere on the internet and youtube.

What I do want to talk about, however, are the oddities I discovered while assembling. This is related to the weird configuration of the Diamondback lower. As I mentioned in previous posts in the series, the Diamondback DB-10 upper receiver was configured to take DPMS parts, so I assumed I needed DPMS parts for the lower as well. Silly me.

The first clue that something strange was going on was the magazine release. I installed the spring and release, started screwing the button onto the shaft, pressed the button and screwed the shaft into the button until the top of the shaft was flush with the face of the button, released it and…the button wasn’t seated in the receiver. Hmm. Looked like the shaft just wasn’t screwed in far enough.

I pushed the button back in (after lining it up with the hole in the receiver) and screwed the shaft in as far as I could get it to go. that did the trick, the mag release fit now and seemed to operate just fine, but the shaft was sticking out past the face of the button by about 1/8″. It was painful to press the magazine release because the protruding shaft would dig into my finger.

Long story short, I ended up using my dremel tool to cut the extra 1/8″ off of the shaft.

The next thing that hinted something wasn’t right was the bolt catch pin. On AR-15’s and Armalite AR-10’s, the bolt catch is held in place with a roll pin. In my DPMS lower parts kit, the bolt catch pin was threaded on the end. Hmm. Can’t screw a threaded pin into a receiver without a threaded receptacle.

I dug into my spare parts bin and used a standard AR-15 roll pin to install the bolt catch. It seemed to fit fine.

Everything else went uneventfully…but after it was all together, the bolt catch wouldn’t catch the bolt.

After getting a magazine and trying it, the bolt would lock open on an empty magazine, but no matter what I tried or how I manipulated the bolt catch, I could not get the bolt to lock back without a magazine inserted.

In trying to figure this out, I e-mailed Diamondback and explained my issue. They replied very quickly, but told me that a DPMS parts kit should work.

I did some more research and ended up stumbling across a comment from a person who said they used an Armalite A series LPK with their Diamondback DB-10 lower and it worked fine.

I decided to take a chance and ordered a bolt catch from Armalite for $23. It took a week or so to get it, but after installing the Armalite catch, everything worked as it should. I’m guessing that had I also purchased an Armalite magazine release and Armalite takedown/pivot pins, they would have worked as well.

At any rate, with a little trial and error, it went together.

So, if by some chance you ever purchase a Diamondback DB-10 upper and lower set, just know that the upper takes DPMS parts and the lower takes Armalite A series parts…just to keep things interesting.

Still some finishing touches…more to come…

Next post in the series.


AR-308 Part 3

Previous posts in the series:
Part 1
Part 2

So, now that we’ve figured out what types of parts we need, the next step is to figure out exactly what to order.

The goal was to make a custom rifle, as accurate as possible…preferably sub-moa, but also keep it under $800 all-in. A lofty goal.

I had an idea of what I wanted, but I didn’t want to rush because I was planning on getting things as I found sales and deals. The best laid plans…

The first thing I found was a 20″ Socom profile barrel made by ELD for $105. I didn’t know anything about ELD but I looked up some reviews and didn’t find anything bad. They guarantee sub-MOA performance with match ammo so I took the chance. For that price, I figured even if I have to buy a new barrel in a year or so, at least it would get me started.

I bought it from Omega Manufacturing. I did find some bad reviews about Omega manufacturing and apparently it’s owned by a parent company that also runs a couple of other online gun parts retailers. Basically, the reviews weren’t about the parts they sell, but about their customer service…so again, not a show stopper as I was more concerned about getting quality parts than excellent service. Turns out, they actually were pretty good. Got my parts out quickly and resolved the one issue I had.

While I was there ordering the barrel, I looked around at what else they had. They actually had really good prices on quite a few parts, so I ordered several things from them in addition to the barrel:

Omega Manufacturing M-lok 15″ free float handguard – $53
Omega Manufacturing muzzle break – $35
ADK Defense Bolt Carrier Group and charging handle – $110
Ejection Port Door assembly – $9
Rifle Length gas tube – $10
AR-15 Forward Assist Assembly – $10

I ordered a cheap low profile gas block for $6 from Cheaper Than Dirt; I ordered some other stuff at the same time, so call it $1 for shipping.

OK…so I pretty much had everything for the upper on order in one fell swoop…so much for taking my time and buying stuff as I found it…but I still needed the lower parts. I really wanted a Luth-AR MBA-1 stock because of how adjustable they are, but they aren’t cheap. Usually around $160. I finally found one at Schuyler Arms for $120 + $7 shipping and as a bonus, it came with the LR-308 buffer kit and a DPMS LR-308 Lower Parts Kit minus the fire control group.

So the final piece was a fire control group from a cheap $29 LPK I already had.

So, that’s where we are: One AR-308…some assembly required (click to make bigger).

Note: There is a vital component missing from this picture. 100,000 internet points to anyone who can figure out what it is. (hint: It’s a fairly small part, but it’s not a spring or pin or anything like that),

More to come…

Next post in the series.


AR-308 Part 2

Previous posts in the series:
Part 1

So, after getting a great deal on the upper and lower, I needed to start getting the rest of the parts. This is where it got complicated.

It seems there is no “mil-spec” for the AR-10 style rifle because they were never made for the military. Apparently there are two primary styles with different variants and even more “one-off” types from various manufacturers.

The two primary styles are the Armalite style (this is the only style, by the way, that can really be called the “AR-10” since AR stands for “Armalite Rifle”).

Armalite style AR-10’s come in two variants: A series and B series. They are not interchangeable as the receivers are milled differently. The most obvious difference between the two are the magazines. The A series uses magazines that look much like a scaled up AR-15 magazine. This magazine style became the “standard”; it’s used in DPMS lowers and is produced by many aftermarket manufacturers including Magpul. The B series uses an aluminum magazine based on the M-14. The magazine release and bolt catch are also different.

The other primary style is the DPMS pattern. There are a few different variations and many manufacturers that produce receivers ostensibly in the DPMS pattern do so in non-standard ways. Basically, there is no guarantee that uppers and lowers from different manufacturers will work together even if they describe themselves as DPMS pattern or Armalite pattern, and DPMS and Armalite definitely won’t work with each other. It seems to be the best bet to buy the upper and lower from the same manufacturer to ensure they’ll work correctly with each other.

In addition to the uppers and lowers being different, many of the other parts are specific. One of the big differences between Armalite and DPMS style rifles is the barrel nut threads. Armalite uppers take a 1 7/16″ barrel nut threaded at 18 teeth per inch (TPI). “Traditional” DPMS uppers take a 1 7/16″ barrel nut but threaded at 17 TPI. More recently, DPMS has introduced a generation 2 upper that takes a 1 5/16″ barrel nut threaded at 18 TPI.

There are also three variations of DPMS upper height. The two main ones are high and low. The third one is apparently rare and is called “high rise” or “slick side”. This becomes important with railed handguards. If you get the wrong handguard for the upper height, the rails won’t line up.

Whew! Talk about confusing.

One thing that helps is that some of the parts are interchangeable with AR-15 components. I found this handy website that goes through all the parts and what is interchangeable.

Just in case that isn’t confusing enough, it turns out that my Diamondback receivers are sort of a combination of DPMS and Armalite.

The rear of the upper and lower where they fit together (the area between the takedown pin and the buttstock threads) are shaped like an Armalite (DPMS is more rounded there), but the upper takes a “traditional” DPMS barrel nut and matches the DPMS high rail profile.

The lower apparently works best with Armalite series A parts (I figured this out through trial and error). I read in the reviews that only Diamondback proprietary pivot and takedown pins will work, so I ordered them, but then I read later that Armalite A series pins work…I didn’t try those, but based on other discoveries I made, I’d guess it’s probably accurate.

At any rate, here’s what I ended up using:

Upper and Lower: Diamondback

Upper parts:
Barrel, extension and barrel nut: DPMS (traditional) style
Gas block and gas tube: AR-15
Bolt and bolt carrier: DPMS style
Charging handle: AR-15
Handguard: DPMS high
Ejection port cover: DPMS
Forward assist: AR-15

Lower Parts:
Takedown and pivot pins: Diamondback*
Takedown and pivot pin springs and detents: AR-15
Safety, safety spring and detent: AR-15
Grip: AR-15
Fire control group: AR-15
Buffer and buffer spring: DPMS (these are interchangeable with Armalite)
Buffer retainer and retainer spring: AR-15
Magazine release: DPMS (modified**)
Bolt catch, spring, detent and roll pin: Armalite series A
Stock: AR-15

*As I previously mentioned, I bought proprietary takedown and pivot pins from Diamondback, but I read elsewhere that Armalite A series pins would work. My guess is that’s accurate based on the fact that I needed an Armalite A series bolt catch.

**The DPMS magazine release “almost” worked. I’ll go into more detail later, but I had to “make” it fit.

More to come…

Next post in the series.


Latest Project: AR-308

Actually, one project among several this summer, but this is the only one that’s gun related.

I love the AR style platform, but I’ve always been interested in something bigger than a varmint cartridge. I know you can make an AR work with 7.62×39, .300 AAC Blackout, 6.8 SPC etc, but I wanted a true “battle rifle” loading.

So, I’ve been interested in getting an “AR-10” style AR platform rifle in .308/7.62x51mm.

The problem is that they’re kind of pricey, typically somewhere between $1000-$2000 (or more…just for the rifle, not including accessories or scope).

I just happened to run across a sale on a blemished Diamondback DB10 upper/lower set. I got them both for $129…about half what I’d expect to pay. The “blemish” involved a lack of anodizing inside the mag well on the front and rear surfaces.

On the rear surface, there was also a flaw in the machining, you can see it on the left edge of the groove about 3/4 of the way down (as always, click to make bigger).

I doubt that it would have affected the magazine fit, but I didn’t like it so I cleaned up the groove with a jeweler’s file and then hit it with Alumi-Black. This is what it looks like now.

I think it cleaned up nicely. That was the only real issue. The fit between the upper and lower is perfect. The only other very minor issue is that the finishes don’t match perfectly, the lower is just slightly shinier than the upper, but that’s not even noticeable with the rifle assembled.

Here’s the upper and lower mated together, along with a standard AR-15 upper and lower for comparison.

More to come…

Next Post in the series


CZ-82 Success story and guest post

Update at bottom

Someone who stumbled across my CZ-82 posts wrote me to tell me about his project.

He broke down, stripped, blued and reassembled his CZ-82.

The final product looks great and he graciously granted me permission to post the picture and the process he used.

As usual…click to make bigger.
Looks really nice doesn’t it?

To answer your questions before you ask:
1: No, the serial numbers haven’t been altered, I used the smudge tool in Gimp to blur them out.  Privacy and all that…

2: He got the grips from and reports a perfect fit out of the box with no fitting.

These are the steps he used for stripping and blueing, as passed to him from another helpful gunney:

1.  Stripped paint with Jasco paint stripper/remover from Lowes/Home Depot. Don’t forget to remove your grips and move them well away from your work area.  This process may take a few applications.  I used a brass and nylon brush to remove the loose paint and get inside of internal parts of the gun.

2.  Once stripped, I saturated it with degreaser (BC Gun Scrubber), just to make sure all paint and oil was removed.

3.  Of course this process removes ALL paint, so don’t be shocked when your white dot sights go away (this can be taken care of easily later).

4.  I used 600 grit, cloth backed, wet/dry sand paper to begin the polishing process.  Use long strokes to go with the grain of the metal.  I left the top of the slide alone as not to polish off the matte.  I then move to 00 steel wool, and then to 0000 steel wool.  Clean and degrease when done (steel wool has some oil in it that needs to be removed before bluing).

5.  I used Oxpho Blue, 100% cotton cotton balls, Q-Tips, 0000 steel wool, and some chop sticks (for dipping cotton balls into the bluing), and a blow dryer for heat.  Don’t forget to glove up for everything after the initial stripping of paint.  Oxpho Blue supposedly doesn’t have a problem with oil from fingers, but I wasn’t willing to risk it.

6.  Heat the metal and use long even strokes with an Oxpho Blue covered cotton ball and/or swab.  It will dry quickly on the heated metal and begin to oxidize / rust.  Give it a minute to sit (60 – 120 seconds) and then burnish well with your 0000 steel wool.  To really get a good blue you need to spend the time to burnish well.  This process evens out the blotchiness of the bluing process and preps the metal for the next application.

7.  I repeated this process 6 times before I was happy with the color match and sheen of the cold blue (heat, blue, burnish).

8.  I then took the parts and put them in boiling water for about 3 minutes.  I then applied a slurry of baking soda to all newly blued parts, then after about 30 minutes, I dunk the blued parts back into the boiled water to remove the slurry.  This process neutralizes the acids in the bluing process and begins to help eliminate the smell.

9.  I then use a light gun oil, like Rem Oil or a little CLP and some 0000 steel wool and shine op all the blue.  This is really the final burnish for your bluing.

10.  (This one is an extra step, but a recommended one) Now to completely remove the smell I put the blued parts in a gallon ziplock bag filled with motor oil for 48 – 72 hours.

11.  Degrease completely, when clean and dry, oil and grease the gun as you would after a typical cleaning.  Apply a very light coat of CLP to all metal surfaces


The generous gunney who was the originator of the procedure above gave permission to post a picture of his own CZ-82 that he refinished using this procedure.

Again, click to make bigger.

This one has original grips which the owner obviously did some polishing on as well.  Very nice job on both the metal work and the grips.

These little guns really clean up nice…and they shoot great too.


Graduation Present

As I mentioned a couple of posts ago (which was a while ago, sorry), My son graduated from Old Dominion University last weekend.

College graduation is a big deal in our family because relatively few of us have attained it.  I’ve only completed an Associates Degree myself.  I graduated Summa Cum Laude with a 4.0 grade point average, but it took me ten years to do it.

My son is not a gifted student.  He’s always had to work very hard to maintain his grades and he’s always done so.  I’m very proud of his Cum Laude honors and the effort it took for him to maintain that level of excellence while, at the same time, working full time, going to school full time and supporting his wife and child.

But I digress.  The point of this post is the project I was working on for his graduation gift.  I wanted to give him something significant and meaningful, but didn’t have a bunch of money to spend…so I decided to use something I already had as a base for the gift and just put in the time to make it special.

He had gotten his concealed handgun permit as soon as he turned 21, but has never had the money to buy a gun to carry.  I happened to have a couple of “spare” CZ-82’s which are great little guns for concealed carry and are pretty much ideal for lefties (which he inherited from me), so I decided to do a complete rehab and refinish on one and give him that for a graduation gift.

As with my carry gun, I did a detail strip, sandblasted the major parts and parkerized it, lightened the magazine catch spring, did a basic trigger job and put a 16 lb Wolff recoil spring in it.

I’m very happy with the way it turned out and he was very happy with receiving it.  It’s not as high speed-low drag as many other handgun models out there, but I’ve found them to be reliable and accurate and I hope that the work I put into it will give it some sentimental value to him someday.


I didn’t have the money to buy new grips for it yet, but that will be in its future (maybe Christmas or a birthday?)


After refinishing the metal, I repainted the sights and protected the new paint with clear nail polish.

The only thing I’m unhappy about is that it actually came out better than the one I parkerized for myself.


Although I’m happy with mine and the finish has proven durable and lasting (I’ve been carrying mine daily for over a year now), the finish came out a bit lighter green than I was expecting.

I re-used the same parkerizing solution to do his and his came out more of the dark Charcoal gray that I expected with mine.

Either his gun ( a bit newer than mine based on the serial number) is made of a different alloy, or, more likely, the parkerizing solution just needed a bit more seasoning to get that full, deep color.

Now I’m considering re-doing mine to get it the color that I want.

One thing that was different about his is that the mainspring plug and lanyard loop is made of aluminum rather than steel so I couldn’t parkerize it.  I didn’t realize this until I was in the middle of sandblasting it so I already had it stripped.  I just used Birchwood Casey’s Aluminum Black on it to protect and match the finish as well as possible.  In the future, I’ll know to check that before I start going crazy with the sand blaster.

Here is a picture of all three of the CZ-82’s in my collection.

The top left one is the one that I haven’t refinished yet.  Its original finish is in the best shape of the three and I may leave it stock.

The middle one had the worst finish to start out with.  It was very beat up  when I got it.  That’s the first one I refinished and is the gun that I carry every day.

And the bottom right one is the one now residing in my Son’s gun safe and that I hope he will be carrying regularly from here on out.

I’m very satisfied with how it came out and I hope he’s as pleased with his as I am with mine.

BTW:  No, the serial numbers have not been filed off.  I used Gimp photo editing software to smudge them out in the pictures.


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’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.


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