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


3 thoughts on “NM Rifle Build Part 5

  1. Very Nice…Is the flag laser etched into the the lower? If so, where did you get that done?

    Also, is it a match rifle?

  2. Yes it is laser etched, came that way from spikes tactical. They do it for an extra $5 when you order a lower. They are having a sale right now on lowers for $89.95.

    No it isnt match, it is just a plain old A2.

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