Re: AR15 Head spacing barrel and bolt
When I went to a major AR/M4 manufacturer's armorer training, we were told not to worry about it. Everything built to spec, etc, etc. 3 years later, time to recertify, that manufacturer wasn't holding a class near me, but another major manufacturer was, so I went to that class. This instructor taught that you absolutely needed to check, talked about component wear, tolerance stacking, etc. Then took one ot my rifles and checked it and it wouldn't close on a go gauge. I check all of our rifles at every inspection now. Also, just because the barrel is stamped 5.56, it may still be chambered/throated for 223. I have 3 rifles in our inventory like that, marked 5.56, throats are .223. It took me a while to determine why they were blowing primers on XM-193 ammo. It is always better to know for sure what you have, markings can be wrong, reams worn out, maker hung over, who knows. Check 'em, then YOU know.