- Apr 7, 2016
- Reaction score
I got a little out of sequence here.You can check for the carrier over-travel by inserting your BCG into the assembled lower w/RE. You should have about at least two U.S. quarters of a gap between the back of the gas key and the lower. Also good to check that your spring when fully compressed over the buffer still exposes the bumper pad on the rear, in addition to it being proper lenght.
Gunsmith/Instructor Chad A. from School of the American Rifle also talks about how if the threads on the lower, receiver extension, and castle nut pass class 3 gauging, that staking isn’t required, but still a good safeguard. He also mentions using Vibra-Tite VG3 in addition to staking on lower/RE/castle nut assemblies with a loose fit. Either way, you have to live the threads to get a proper torque reading. Plus it protects against corrosion on the aluminum/steel thread interface.
I haven’t thought of doing a reverse torque test on the castle nut, but that is something I have done on the gas key screws.
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The reverse torque test of the two gas key nuts was on the School of the American Rifle. It is what he does when doing a general verification of a bolt carrier.