Headspacing an aftermarket barrel

[Qbert]

Hypothetical question: Let's say you know what the base to datum line measurement is on a PTG headspace go-gauge. Couldn't you just - using your Hornady headspace comparator thingy that attaches to your calipers - find and use a virgin piece of brass that has the same base-to-datum measurement as the PTG...and use that as a cheap go-gauge? And find another piece of brass that measures .004" longer and use that as a no-go gauge?

Thanks for any thoughts or enlightenment. I'm not the sharpest tool in the shed, but I'm learning.

[sixonetonoffun]

I think your over thinking it. Unless it's a fireform case. Otherwise sized virgin brass go. Add tape no go. Double check or triple check. It worked for me and many before me!

[cranebird]

Hypothetical question: Let's say you know what the base to datum line measurement is on a PTG headspace go-gauge. Couldn't you just - using your Hornady headspace comparator thingy that attaches to your calipers - find and use a virgin piece of brass that has the same base-to-datum measurement as the PTG...and use that as a cheap go-gauge? And find another piece of brass that measures .004" longer and use that as a no-go gauge?

Thanks for any thoughts or enlightenment. I'm not the sharpest tool in the shed, but I'm learning.

My thought is that datum lines suck for trying to duplicate measurements unless you have the given measurement that the datum line is created from. It is difficult at best when not in the knowing where the datum line was established from because you are dealing with round diameters that are usually at a taper from the case design. The only thing to do is rent the gages and create your own once you set your barrel within the gages spec, keep a couple pieces of fire formed brass to reset from. They still will not be exact but should put you within specs.

[earl39]

You won't find virgin brass that will measure out correctly. Virgin brass is by design slightly undersized to allow it to fit all factory chambers.

[Steelhead]

The go gauge is the way to go.
I messed with using cases and thought the to gauge gave a more positive setting.
New brass only gets blown out .002 in my chamber-perfect.

[Qbert]

Thanks, guys!