AR-15 Stock Problem

[BryanP]

A number of years ago I built myself a nice 20" HBAR A2 AR. But our tastes change over time. I recently acquired a 16" flattop pencil barrel upper. So to go with that I decided to swap out the A2 stock for a collapsible. At the last RK show in Murfreesboro I picked upa Magpul stock, buffer tube, etc...

Since I was going there anyway I had the nice people at a local gun shop put on the stock for me. Yeah, yeah. I know, but I don't have the tool I need and I didn't feel like waiting.

So they put it on and when it's fully collapsed there's a pretty large gap between the stock and the rear of the receiver. They said that's the only way it would fit.

The A2 fit with no problem, so I'm going to say the actual receiver is fine. Question is, what's wrong with the rest of it? Or is this much variation considered acceptable / normal? Anybody have an idea?

[Rightwinger]

You need a carbine buffer and buffer tube.

They are different lengths.

[BryanP]

I bought the buffer and tube from the same guy who sold me the stock. It's not an A2 buffer and tube.

[Guest bart_p]

Something is not right there. You should only have the width of your end-plate and castle nut between the back of the receiver and the front of the stock. How many positions does the buffer tube allow for adjustment?

Bart

[BryanP]

Something is not right there. You should only have the width of your end-plate and castle nut between the back of the receiver and the front of the stock. How many positions does the buffer tube allow for adjustment?

Bart

Six in theory, but I can only seem to lock into 5. ???

[Rightwinger]

Is there an extension on the buffer tube? Smaller section that can be unscrewed and removed or one piece tube? Tube may not be of same or compatible with the stock.

[BryanP]

Is there an extension on the buffer tube? Smaller section that can be unscrewed and removed or one piece tube? Tube may not be of same or compatible with the stock.

That's pretty much what I was thinking. IIRC, it was one piece.

[Reservoir Dog]

I'd like to see a pic of your gun with the stock taken off. With special attention paid to the end of the receiver extension (buffer tube).

Couple of observations:

- You appear to have a mil-spec Magpul MOE stock. Correct?

- Oddly, the threading on your buffer tube looks like a commercial spec tube.

Commercial tubes are a little longer than mil-spec tubes, and they have an angle cut on the end of the tube. Mil-spec tubes have a flat end. It almost seems that you have a mil-spec stock on a commercial tube.

Does your stock collapse and expand easily, or is it very tight and difficult?

Bryan, you have my phone number. Give me a call, if you want, and I'll see if I can figure it out.

Edited April 2, 2010 by Reservoir Dog

[BryanP]

I think you nailed it Reservoir Dog.

The vendor at RK had boxes of both commercial and mil spec. I picked up a mil spec stock and asked him to get the rest of the parts I would need. Apparently he didn't pay close enough attention and I didn't know enough to know the difference.

I just took off the stock and the rear of the buffer tube does indeed have an angle cut so that it is slightly taller at the top than the bottom.

I can't remember the name of the vendor I bought it from. I guess I'll pick up a commercial stock to go on it and sell the mil spec.

Oddly enough the stock wasn't that hard to collapse or expand.

Thanks for all the help guys. Much appreciated.

Anybody know of a local shop with commercial MagPul MOE stocks on the shelf or should I order one?

Edited April 3, 2010 by BryanP

[Reservoir Dog]

Cool! Glad we got if figured out.

Oddly enough the stock wasn't that hard to collapse or expand.

That's surprising. Mil-spec tubes are also slightly smaller in diameter than commercial tubes, so the stocks are made a little smaller to fit properly. I am actually surprised that you were even able to get the mil-spec stock on a commercial tube.

One time, I accidentally put a mil-spec stock on one of my commercially tubed ARs. I could not move it, and liked to never got it off.

[BryanP]

I know. I checked and a milspec is 1.15" in diameter, while the commercial is supposed to be 1.17". The stock is a mil spec and the buffer tube has the angle cut you mentioned, but it still moves freely. If it closed all the way I'd never have known.

[Guest bart_p]

I think you should keep the mil-spec stock and replace the buffer tube to make it mil-spec. If you plan on running the gun hard you will never know why I told you to do so. Alternately, if you keep the commercial buffer tube and you run the gun hard, then you take the chance of finding out why I prescribed you to do so. Make sure whatever you do that your castle nut is properly staked.

By the way: When I say running a gun hard, I mean putting a few thousand rounds through it in a week or less during high stress training/classes. If it is a fun gun, then no worries on being mil-spec.

Bart

[BryanP]

bart, I'm not sure what the logic is there. Everything I've been able to find says that the commercial tube is actually stronger than the milspec tube insofar as it's a bit thicker.

And yes, it's basically a fun gun. For actual defensive purposes I'm still likely to reach for my .357 and my 12ga before anything else. I was thinking of taking a carbine course at some point, but it would likely be a one-day class, not a week and thousands of rounds.

The main reason I originally chose milspec was because there are so many more stock options available for it than the commercial tube. But the stock I actually want is available for the commercial tube, so it's no big deal.

That said, I may call Outpost today and see if they have any milspec tubes in stock. We'll see.

Edited April 3, 2010 by BryanP

[Guest bart_p]

The problem with the commercial tubes is that the threaded section is also 1.170". This means that the threads are not cut to the full height as the mil-spec tubes and the threads do not fully engage the threads in the receiver. They can fail because of this and potentially pull the threads out of the receiver and render your lower a paper weight. Granted, this is not very common, but in my opinion the TDP specs should be followed as closely as possible when building a weapon intended for hard use. But you said it's a fun gun so like I said, no worries. Just a tid bit for future reference.

Bart

[BryanP]

And my stock has been fixed.

First off, Outpost Armory in Murfreesboro rocks. I went by there this evening and showed one of their people my situation. We determined that my cheap gun-show buffer tube (and I won't say inexpensive - apparently I bought cheap crap), was neither fish nor fowl. It was milspec diameter but commercial length. As a result, a milspec stock would fit over the tube but not close the entire distance, and a commercial stock would close all the way but rattle loosely because it didn't fit snugly enough.

I bought a proper milspec buffer from them and had it put on. I was out the door in about 30 minutes.

Edited April 6, 2010 by BryanP

[Reservoir Dog]

[Guest bart_p]

Glad to hear you got your problem resolved.

Bart

[Sidewinder]

A number of years ago I built myself a nice 20" HBAR A2 AR. But our tastes change over time. I recently acquired a 16" flattop pencil barrel upper. So to go with that I decided to swap out the A2 stock for a collapsible. At the last RK show in Murfreesboro I picked upa Magpul stock, buffer tube, etc...

Since I was going there anyway I had the nice people at a local gun shop put on the stock for me. Yeah, yeah. I know, but I don't have the tool I need and I didn't feel like waiting.

So they put it on and when it's fully collapsed there's a pretty large gap between the stock and the rear of the receiver. They said that's the only way it would fit.

The A2 fit with no problem, so I'm going to say the actual receiver is fine. Question is, what's wrong with the rest of it? Or is this much variation considered acceptable / normal? Anybody have an idea?

Still got that 20" HBAR upper? Want to sell it? Just checking?

[BryanP]

Still got that 20" HBAR upper? Want to sell it? Just checking?

A friend of mine has first dibs on it. If he decides he doesn't want it I'll see about putting it up for sale at a later date.