Hank
I'm reloading for 7mm prc. 160 grain acubond bullet. Using imr 7828 scc powder. 66.8 grains was what came up. This over pressured. Fps was 3220. Can anyone tell me how much to back down on grains to make it not over pressure.
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I hadn't seen this until now. I double checked a couple of load settings and believe the 66.8gr used is just under 3000fps using xxl and a 26" barrel. The closest data using the 162 X bullet using the same 66.8gr value pushed it to 3075. The only time I have seen this happen before was a bad CIL L3 value either cut short in the chamber or the brass was not trimmed. The interference of this dimension is very small and if the neck gets pinched against the bullet. So the cartridge is fighting to expand the neck to release the bullet. Very common on military 556 where you see the neck ripped off. Both IMR7828 & IMR7828SSC are explosive and the SSC type more so. My calculations attached.