I change barrels a lot, using fired cases, an RCBS Precision Mic to measure case headspace, and plenty of time. I resize cases with a Lee Collet Die, and almost never FLS. Some case dimension can/does change such that a FIRED .000" headspace case will NOT go in a barrel headspaced with a .000" headspaced FLS case.

After firing 223 cases in a Stevens 200 bbl, and changing to a M12 HV bbl, the .000 headspace cases would NOT go in the M12 bbl. headspaced with fls .000" cases. FLS the ,000" headspace fired cases keeping headspace .000", and the cases fit just fine in the M12 bbl.

I suspect that the M12 fired cases WILL fit in the Stevens 200 bbl. I don't know WHAT dimension increases in the Stevens bbl.


Headspace with fls fired cases only!