Gentlemen and Ladies,
Yesterday I was shooting my M39 Finn Mosin Nagant rifle with PPU brass. After firing, and before sizing, I checked the shoulder with a Hornady Headspace guage with my calipers. To my surprise, the brass is stretching .025" after firing. Is this normal for a rimmed case? Thanks.
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Rimmed cases stretch upon firing, just like rimless and belted cases. When you fire it, the brass stretches to fill the chamber, thus the term “ fire forming”. If your rifle has a very sloppy oversized chamber you will get more stretch, or if the headspace is off, you will get excessive stretching.
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Should I just size the shoulder back a few thousandths by backing my sizing die off? I'm probably overworking my brass by full length resizing. Using Lee pacesetter dies.Originally Posted by JeffreyDeGraff
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That is what I would do.
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Thanks
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Nice fire formed brass now . Neck size and bump a couple thousandths
I don't have a neck sizing die yet. It's on my list to get. I bumped the shoulder back .002 to .003" and it chambers fine. Need some bullets and powder and I'm ready to load some ammo.
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Keep us posted. I’m working over an old m38 for my son for his first deer rifle. Waiting for the last of the pieces and parts to come in.
JTD
Will do. I need to see if my barrel is .308" or bigger. A 308 muzzle guage won't even start in the muzzle.
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Loading up 15 test loads for my Finn M39. 150 gr Hornady fmjbt boolits from Wes, some IMR 4895 powder, and WLR primers in PPU cases.
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