Japanese Militaria at Castle-Thunder.com

[Mosko]

Thanks to you guys with the help on the 99. The good news is, the rifle and head space are fine. I screwed up the ammo we were firing. With the correct length cases, she shoots perfectly!
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Mosko

[mag]

I missed the first part with your problem. what happened? what load were you using? As always I am interested in the shooting part. mag

[Mosko]

We were firing a t99 with formed 7.7 from 8X57 new Remington commercial brass. At shot #15 or so the cases started coming apart half way down. It looked like a head space problem in the rifle. I later learned the shoulder was .040" too short, which was technically an excessive headspace problem. The 1st 15 shots showed evidence of severe stretching, but I didn't notice that until whe had the case failure. we thought at first that the commercial brass was thin, but it was my forming mistake instead.

The cartridge was constructed using .311 pulled Russian light ball bullets, remington commercial 8x57 Mauser brass, WLR primer and 39 grains of M9 surplus powder (IMR-3031). This is a beginning load about 2300 fps for the first loading to fireform, so there weren't any pressure problems involved.

The strange thing, is that until the chamber heated up with the 1st 15 shots, the short brass formed to the 7.7. The hotter the chamber became, the worse the stretching until they started separating.
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Mosko

[mag]

Ok, Thanks for sharing. I just neck size my 1st time 8mm brass with a 7.62x54r die, just enough that it will just fit in the rifle. That lets the ripple in the neck hold it in place for the fireforming, easier on the cases that way. Your load is a good one. My overall best is 40.0 of I-3031 with the Hornady .312 150 sp. mag

[Mosko]

Thanks for the tip on necksizing with the Russian die, I hadn't thought of that.
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Mosko