.444 Marlin headspace hair-pulling

I'm rebarrelling a rifle to .444 Marlin. I just lre-earned that headspacing a rimmed cartridge isn't as easy as I expected.

A rimless cartridge, the distance from the base to the shoulder is fixed within narrow limits at time of manufacture; usually no more than a few thousandths at most. Rimmed cartridges seat on the rim. Cool.

The SAAMI drawing for the .444 cartridge says the rim thickness for the .444 Marlin is .064-.010, or .053-.063. That's a .010" variation between the limits.

.444 GO gauges are .063, and NO-GO are .067; that's .004" maximum headspace.

If I set up for zero headspace on a .063 rim, I should be okay; I've never seen a thicker-than-spec rim on anything. But even with zero headspace on .063, a minimum rim can give me a headspace of .010" - or .014" if I'm on the edge of the NO-GO with the .064".

How likely am I to see thin rims in .444 brass? I ran into this once, years ago, with a .45-70 conversion, with rims all over the place, and wound up standardizing on one brand of brass so I could keep the headspace consistent.

I've only got RP and Hornady brass, but they both seem to be around .060"-.062" and I suspect thinner ones (RP) the caliper was actually getting into the bevel on the edge which was more pronounced than on the Hornady brass.

What kind of rifle are you working with? I have zero .444 Marlin experience but I am interested in your project.

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Moleman:
Thanks. I ran into so much variation on .45-70 brass I'm always leery of rimmed cases now.

TBG:
Unless a bolt of sanity strikes, the intended victim is a Saiga .410 shotgun.

On the one hand, it already feeds .444s from the stock magazine into the .410 chamber, then extracts and ejects them, with no fiddling with the magazine, feed ramp,or extractor. On the other hand, the breechface on the Saiga is absurdly complex; the back of the barrel also forms the feed ramp and a "hood" to guide shotgun shells to the chamber; the rim is maybe 3/4 inch down in there. Every time I look at that I get the urge to close my eyes and back away slowly...

My only suggestion would be to get a barrel blank longer than intended and turn the first 6" or so to the trunnion diameter so that need be any errors could be lopped off and started over. Not having the stub threaded means you'll only have to cut off the hood length to start over.

SO- basically a .444 AK! That would be cool. Buy a brass catcher!

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