Questions about my first AR build???

[NugginFutz]

The procedure that LRRPF52 and Midway were talking about is to lap the bolt to the lugs inside the barrel extension.

Squaring the upper receiver to the barrel extension is another matter. The uppers are not always square to the bore. Brownells sells a lapping tool that can be used to square it up and make sure you have 100% contact around the upper receiver to the barrel extension. Then you get into, is the barrel nut machined square, are the threads on the upper machined square, etc, etc. It would be similar to "blue printing" a bolt action receiver. An awful lot of work to chase that last 1/4" of accuracy. Maybe worth it in National Competition, but not a hunting rifle.

I don't have a jig, or know of anyone that has one. I do have a large surface plate and machinist squares, so I'll check it that way. If necessary I can turn a jig on my lathe and lap the upper, but from what I've read the VLTOR's are machined pretty well.

What he said.

Because some of my rifles do shoot for that last 1/4", I find the effort worth while. Just not explicitly for a hunting rifle, as CC says.