AR barrel shimming

[openclassterror]

1.010 receiver bore is ridiculous. .9975 on the extension is at the extreme limit of tolerance as well. Add them together and it is like throwing a hotdog down a hallway. You can bed them together with shims or epoxy, but I would toss the upper for sure. Even the $30 Anderson uppers are never that loose. Good uppers are too inexpensive (in the big picture) to try getting by with a poor one.

[kurtm]

Sigh, we are talking wraping the ENTIRE extention in shim stock and then heating the upper so the shim stock AND extention enter the upper making for a light tight fit. I've also had good luck wit the Loc-Tite fix. All we are looking for is a barrel to receiver fit with no slop. It doesn't matter what dimensions that " it should be thrown away at" or anything else shim it or glue it so it doesn't move and all will be well.

If you feel your receiver is junk because Mr. XYZ says its crap send it to me and I will use it to make an accurate rifle.

Note: this is not to say that Tom's advice is bad, far from it. I suspect there aren't too many folks that know these specs inside and out like he does and when he says "hotdog and hallway" I would listen, but I have also found that as long as it doesn't just bang the hell out of the sides either with a shim or filler almost any combo can be accurate!

Edited June 16, 2015 by kurtm

[mike4045]

Been using the Loctite fix like Kurt said for about 10 yrs. No issues so far.

[bmiller]

Which locktite do you recommend Kurt?

[openclassterror]

To note, I didn't say that he SHOULD throw his away, I said that I would, if it was mine. I am well aware that pretty much any method of tightening the gap is productive as long as the extension can't "squirm" in the receiver. BUT, I am anal-retentive about gun builds, and uppers are cheap. If I got one in for a customer's gun that fit so loose, it would go back to the maker. One advantage to using "mil-spec" parts is that if it is out of tolerance from the GI print, you can generally get the manufacturer to replace it. Ditto the names with reputations (like JP). One phone call is generally enough to get satisfaction on a bad part.

Kurt, I may have a bucket of parts (or more) that are serviceable, but not good enough for me to feel good about putting on a top-tier build. A different attitude is required when building a gun with my name all over it for a customer versus, say, a varmint gun that I use myself. Lemme know what cast-offs you need, and I can look through what I've got for ya