Re: Mosin Nagant Headspace?
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: JLM</div><div class="ubbcode-body">Okay thanks for your help again.
How do you gauge the bolt to see if the length is right?
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I've done it by taking a sheet of paper (which generally has a very stable thickness through the sheet) and putting slips of paper on a shell base, continuing to build it up until the bolt closure gets very difficult.
Take it apart and measure the final crushed thickness of the paper, this will get you an idea of how far off the bolt might be.</span>
I've never dealt with rimmed carts before, and after looking at the gauges it appears as if the 'headspace' is between the end of the rim and the end of the chamber, and NOT to the shoulder.
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Correct, those were built to space on the rim, like many rimmed cartridge rifles are. A very easy way to improve accuracy is to set back the barrel so it spaces on the neck before the rim, but only just BARELY maybe under 10 thousandths</span>
Nonetheless it seems (to me anyway) that if the chamber is still too long your brass has to stretch somewhere and the potential for it to split somewhere is there.
<span style="font-weight: bold">Yes, it certainly sounds like this is the problem. You might have a proper bolt length and a bad chamber. Wartime production being what it was in Russia, there's a good chance they just said "screw it" and sent it to the line. I've taken corrosive surplus ammo from wartime, pulled the bullets and dumped the powder and bullets into new cases with non-corrosive primers. Doing this I found a couple pieces of grass seed in the powder. "Floor sweepings" was the way a CR fellow rationalized it to me. I've seen it in Turkish 8mm ammo too.</span>
I have the one case that blew out .058 longer and it has a crack on the shoulder itself. Thought that was weird, you'd think it would head sep first but.....
<span style="font-weight: bold">Try cutting one of those cases in half and take a look how thick the web on case head is, for the suplus ammo I wouldn't be surprised to find out that it's very thick so that crappy MG's can shoot it without sticking a separated case in the chamber.</span>
Thank you sir
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I'll send my dad a link on this thread and get his take on it, he's worked on a number of MN's over the past few years, he might be able to diagnose it immediately. He's a pretty decent 'smith and likes to tinker with CR rifles, so he maybe be able to offer you a cheap solution if the "extra long" chamber is the issue at hand.