Not problem. Shims then. Just trying to give information.
I just bought the tool. Lapping compound is JB bore compound I already have. Or a tube of lapping compound from autozone will work. Gun products cost more. In a pinch even tooth paste works. No need for a drill either. Turning the tool by hand works. Just takes more time. Necessity for lapping is debatable. It may not be needed, neither is shimming. But sometimes it is. I have seen it a few times, especially with budget milspec parts.
-TL
PS. The tools actually came with a jar of compound. I didn’t use it. JB cuts slower, so I use that instead.
Good idea. Didn’t think of that. A rat tail file would do too. Just remove enough metal to allow the gas tube through. Thanks I will bear that in mind when it becomes desperate next time.
Don’t get me wrong, your’s is certainly a better solution and the solution I would use now that I have started lapping…I just tried to keep it fairly simple as it was his first build.
I don’t have the patience for hand turning! I use 600 grit compound, which takes a bit even with a drill.
I got the shims from Bison Armory and installed the thinner one, which did the trick. Once installed it only took a hair over 30 ft. lbs. to get it indexed. I installed the gas tube, hand guard and function tested. Everything looked good so I put it on a known lower and took it out to my range for some live fire. It ran like a top, no issues at all. Now on to build the matching lower. Thanks all for the help, I may be back once I start on the lower.
You put the shims between the receiver and the barrel flange. Do not put them under the nut.
The receiver and barrel do not move relative to each other when you tighten the nut, therefore the shims only get squeezed. If you put the shims between the barrel flange and nut, as you torque
the nut, the nut will slide on the shim, running the risk of tearing, or wrinkling the shim.