I was playing around, measuring an action that has lug setback. The receiver face to 'C' ring measurement was .630, the barrel shank was .630, and the 'C' ring to bolt face distance was .115

An unfired factory cartridge in an original Mauser 7x57 barrel had .095 protrusion.

Assuming .002 crush fit, does this thing really have .018 headspace?! I have never used a lathe and micrometer to install a barrel, so I'm not sure I'm calculating this right. If this is correct it's pretty scary, I was firing mid-range 270 handloads in it this way.

Todd

Todd---

It sounds like the 7x57 barrel had .020 headspace but you gave no figures on what a GO gauge protrudes from the .270 barrel. That's the one you have to worry about because it's the one you're shooting. The gauge should stick out of the barrel by .115 and not less than .108.

Jack,

Thanks for your response. I didn't measure the 270 barrel, and can't now as I sold it . I guess the most I could say is that the headspace was probably a bit excessive.

I'm just doing this 'figgerin' to plan my attack on this action, which will have the 7x57 barrel permanently installed and placed in a Mannlincher style stock, after the action is re-cased.

Todd

Primer protrusion does indicate headspace, but is not a measure of it. The primer drives the case forward, and sets the shoulder back. There are too many variables involved to make it a measurement.
Good luck!