First build A2. Problems with rear takedown pin.

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[ARCHIVED THREAD] - First build A2. Problems with rear takedown pin.

Posted: 10/22/2015 1:56:19 PM EDT

Hello all,

I just built (with some help) an A2 style AR. There seems to be a problem with the rear take down pin being very tight fitting. I have to use a punch to drive it in and out. The upper is DPMS and the lower is a Bushmaster. The guys that were helping me said the lower was probably out of spec. The front take down pin is tight as well just not as much. Is there any possible fix or am I just going to have to live with it.

Posted: 10/22/2015 2:55:21 PM EDT

[#1]

Lube it up and drive it back and forth several times. Take the rifle out and shoot 100 rounds through it. Use will loosen it up quickly enough. I would rather have a tight fitting pin than a loose pin.

Posted: 10/22/2015 3:47:05 PM EDT

[#2]

you can always take a drill to the inside of the rear lug and very gently and slowly remove a little material?

Posted: 10/22/2015 4:06:07 PM EDT

[#3]

Thanks for the replies. I will go with shoot it and lube it and see if it loosens up method first. If that doesn't work I will take drilling the lug into consideration. I have two other AR's and I can get this pins loose on those by hand. Not easily but not impossible like they are on my build rifle.

Posted: 10/22/2015 8:59:07 PM EDT

[#4]

Meh, it's better than a super sloppy fit. Yeah, I know supposedly that won't hurt accuracy (which I think is debatable), but it's fricking annoying when the upper is wobbling all around. I've seen some pretty loose ones in my time. And yeah, I know there are fixes, but still. I think I'd prefer to just use a punch and have it be stiff.

Posted: 10/22/2015 9:45:56 PM EDT

[#5]

If you decide to modify something, modify the cheapest part... the pin... not the receivers.

Posted: 10/23/2015 12:32:05 PM EDT

[#6]

If it Feeds, Fires and Ejects properly, there's no way I'd do anything to it.

So, IMO, I would leave it be !!! It will loosen up a little in time, don't be in a hurry, just let it happen slowly.

Posted: 10/23/2015 3:59:19 PM EDT

[#7]

Yeah, just stick a punch in the buttstock or something. You can always smack it against the bench or ground or something if you don't have a hammer handy.

Posted: 10/23/2015 4:46:58 PM EDT

[#8]

It is entirely possible that neither of the receivers (upper or lower) are "out of spec", as the term "Mil-spec" is actually a range of measurement rather than just one specific individual number, and so while both may be within "mil-spec" tolerances, both may also be on the low side of the range, rather than the exact middle of the specification, giving you an exceptionally tight fit, but as others have already stated, if you can physically get both pins to close, they will loosen up with repeated use over time. So go shoot it & enjoy the tension while it lasts.

Posted: 10/23/2015 6:14:02 PM EDT

[#9]

Thanks for the advice everyone. Now I wait for this rain to pass so I can get out and shoot the thing.

Posted: 11/7/2015 9:28:06 PM EDT

[#10]

I had the same issue with my A2 build. It loosened up with time.

Posted: 11/12/2015 10:14:02 AM EDT

[#11]

I check the holes in the lower with a .250" gage pin. It should pass through the pin holes smoothly. I have found a number of lowers that the gage pin did not go through. If it doesn't, I ream the lower holes, front or rear as needed, with a .256" straight reamer. Mil spec is the takedown and pivot pin be removeable with finger pressure.

Posted: 11/12/2015 3:39:01 PM EDT

[#12]

I have found that on one of my rifles that is very tight I can push down on the upper and its easier to to push the pin out.

Posted: 11/22/2015 3:05:30 AM EDT

[#13]

Quoted:
Hello all,

I just built (with some help) an A2 style AR. There seems to be a problem with the rear take down pin being very tight fitting. I have to use a punch to drive it in and out. The upper is DPMS and the lower is a Bushmaster. The guys that were helping me said the lower was probably out of spec. The front take down pin is tight as well just not as much. Is there any possible fix or am I just going to have to live with it.

View Quote

My DPMS A2 upper was the same. Light sanding of the rear lug bore allowed the takedown pin to be moved with finger pressure.

Posted: 11/22/2015 3:18:29 AM EDT

[#14]

This is the norm for how receivers are cut for the last decade. Consumers by and large do not want a loose fit.

Posted: 11/22/2015 8:54:02 PM EDT

[#15]

Quote History

Quoted:
This is the norm for how receivers are cut for the last decade. Consumers by and large do not want a loose fit.

View Quote

Yea my A2 build is the same way and I would love my other ARs to be just like it. My lower to upper fit is by far the best on my A2 and I also have to use a punch to take the rear pin out. If push comes to shove and I need to get it out in the field, then I can use a rod to punch it out. No big deal.

Posted: 11/22/2015 9:48:30 PM EDT

[#16]

Quote History

Quoted:

Lube it up and drive it back and forth several times. Take the rifle out and shoot 100 rounds through it. Use will loosen it up quickly enough. I would rather have a tight fitting pin than a loose pin.

View Quote

This. On the handful of ARs I've build everyone had tight pins that need a punch initially.

Posted: 11/29/2015 3:12:42 PM EDT

[#17]

Thanks again for the advice everyone. I have just never handled an AR that was this tight. Still haven't gotten to the range with it yet due to life matters. I will let everyone know if it loosens up after I put a few hundred rounds through it.

Posted: 11/29/2015 4:05:11 PM EDT

[#18]

Put a little bit of grease inside the rear pin hole and on the rear pin to make pin movement easier when under tension.

The dimension that is made tight is almost always the rear of the pocket in the lower were the rear lug goes in. Recoil forces from the upper bear on that surface, and as previously mentioned, will subtly mate those surfaces together and ease the fit after a little bit of shooting.

Posted: 11/30/2015 9:16:19 PM EDT

[#19]

Do as others have said, also the pushing down on the upper always helped me. It took around 1k rounds on one rifle for it too loosen up without using something to separate the two. Shoot and enjoy

[ARCHIVED THREAD] - First build A2. Problems with rear takedown pin.

AR-15 » A2 Builds

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