Built up an AR a couple years ago but other than sighting it in haven't shot it much. Originally I got it with a telescoping butt stock but recently put a full size butt on it(I suppose it's called the A2 pattern). It's made it a much more satisfying gun for me to shoot and carry if I choose to take a gun for a walk in my woods.

However, I don't like the slight movement between the upper and lower. On the one hand, it's not bad at all but you feel it if you are paying attention, so what's the best long-term way to eliminate it? I wouldn't mind putting a set screw under one or both pins, I'm not planning on anything more than using this for coyote hunting.

Not a fan of duct tape shims, probably don't have that clearance anyway, don't need to have reason to field strip it or take it apart anywhere other than a work bench. So for you guys who have black rifle experience, what are some "clean" and competently designed ways to remove the play between the upper and lower?

Thanks!

Mark

they make action wedges for that purpose.

Heres just one a quick search found.

https://www.midwayusa.com/product/100340833

The obvious answer is to have multiple uppers and lowers so you can match up the ones that fit the best.

I invented the Wedge tightening suystem years before the "accu-wedge" came out. I used Pencil Erasers. The Wedge type.

Yeah, and if you make a mistake-----YOU CAN ALWAYS ERASE IT!!!

Couldn't resist that one!

You do have a sense of Humor don't you Tom?

Hip

Since you asked the BEST way to tighten it, the best way is to put an angled screw up from behind the pistol grip that screws into a trunnion in the rear take down pin hole of the upper. Then epoxy bed behind the lug so that the lug has a solid seat to bear against. Tighten the screw to a uniform torque to ensure consistent zero. The screw will draw the upper and lower together, not just push them apart as most make shift methods do. Won a whole mess of matches with such a set-up. Just make sure you plug the take down pin holes in the lower or the CMP may DQ you in the National Trophy Individual match. Don't ask how I know.

John

quote:

Originally posted by gasgunner:
Since you asked the BEST way to tighten it, the best way is to put an angled screw up from behind the pistol grip that screws into a trunnion in the rear take down pin hole of the upper. Then epoxy bed behind the lug so that the lug has a solid seat to bear against. Tighten the screw to a uniform torque to ensure consistent zero. The screw will draw the upper and lower together, not just push them apart as most make shift methods do. Won a whole mess of matches with such a set-up. Just make sure you plug the take down pin holes in the lower or the CMP may DQ you in the National Trophy Individual match. Don't ask how I know.

John

Aeroprecision makes an inexpensive (a few dollars) retrofit kit that mimics their factory system. It does take some machine work, though.

I use the wedges on one of my 6.5 Grendel.

Everything I have is airtight - all matching upper and lowers from Aero, LaRue, and Sons of Liberty.

He asked for the best way. I told him the best way. Not that there are not other ways. Matching just means they sorted through bunch of parts and found some that were tighter than others. See how tight they are after a dozen barrels and tens of thousands of rounds. Yes, mine has likely has had over a dozen barrels in the 20 or so years I used it. It got retired 5 years ago when they changed the rules to allow scopes for service rifle. Trigger and hammer pin holes got wollered out and needed swaged to tighten them back up, but the upper to lower fit was still rock solid and it shot lights out. To bad the shooter does not shoot like he did 25 years ago.

The marine team used the method for a while but decided the gain was not worth the effort, and they broke the rear lug off the upper because they did not bed it into the lower. The AMU glass bedded the upper to the lower for a while but still used the pins to hold them together. I think they gave that up several years ago. In all honesty, the commercial parts we are getting today all fit so much better than what was available 15-30 years ago that the little wedge is really all you need.

I've got a lower that I used for years for test firing. Probably has had several thousand different uppers on it and who knows how many rounds down it. It rattles like a bucket full of bolts, but still shoots small groups. When using it I do use a hard hold with lots of cheek weld to try and hold the slop to one side.

Regards,
John

Thanks for your explanation John, it makes a lot of sense and put me down as someone who would have figured out bedding the lug after I had already broken one off.

However, somewhat similar to an accu wedge in theory does putting a set screw in the lower below the rear lug and essentially "pinching" the lug between the set screw and the takedown pin have any drawbacks, such as possibly elongating the holes in the lower?

At any rate, your initial suggestion was an answer I was looking for and looks like it will be an interesting project in the shop for this winter, thanks!

accuwedge is cheap and easy