Headspace usually isn't the problem with any #1. It is the fact the rifles' chambers were cut so they would work with all ammunition & work in the mud of Flanders (being a fellow Canuck, I shouldn't have to tell you about the Ross fiasco, should I?).

Don't forget the military doesn't / didn't reload.

What I do is neck up new PRVI / ppu brass (made to mil spec) or if you have access to new DI 42-45 brass (Canadian made Defence Industries war-time brass, of EXCELLENT quality) to ~.338 or .357 & then neck them back down so your bolt just closes on the round. Thereafter, just neck size, I use either/both a Redding bushing neck sizer as well as a Lee collett die and even though I also have a Redding body die, I haven't had to use it yet.

If you don't have headspace gauges, a trick I've used is to use one of the small round peel and stick sale stickers you get at the dollar store. Trim to just fit the base of the cartridge. They measure about 0.004" thickness.

btw, all of my old LS's really like cast bullets, especially the heavy ones that mimic the old Mark VI bullet. I've designed a few on accurate moulds and mountain moulds.