11-25-2013, 01:38 AM
AR15 head spacing is sloppy by design. There's no way the mass and inertia of the bolt carrier group can generate enough force to deal with variance in shoulder location like the camming action of a turn-bolt Mauser. So precise shoulder locations aren't an issue, and have to be under-sized to feed in a gas gun. There's no way you're going to affect headspace with lapping, unless you use heavy grit media, and go to town on it for hours after ingesting some serious amphetamines.
You don't need to blue print as far as receiver face is concerned, unless it's obviously out of spec, which will break bolts all day long. Some smiths start from scratch, and will true the barrel extension, all the faces, and go super-anal on it, and end up with a gun that shoots sub-1/2 minute consistently. There is a lot of work involved in getting that extra 1/4" that most people won't bother with.
You don't need to blue print as far as receiver face is concerned, unless it's obviously out of spec, which will break bolts all day long. Some smiths start from scratch, and will true the barrel extension, all the faces, and go super-anal on it, and end up with a gun that shoots sub-1/2 minute consistently. There is a lot of work involved in getting that extra 1/4" that most people won't bother with.