I was out shooting my M95 yesterday, Loaded up 7.62x54r cases resized to accept the .330 FMJ bullet. 42 gr IMR 3031. The rifle is in VG shape, bore was dark with well defined rifling. I focused on fire forming the brass and seeing how the rifle was performing (loading, firing extraction ejecting etc)..
Well I'm not too impressed with the forming of brass using 7.62x54r to make 8X56r. Now it would be fine for 8x50R, but in my opinion and experience there's just not enough brass to make a good re loadable 8x56r cartridge case. I fired 15rds fired, three were fire formed to the chamber dimensions, three formed but split, the rest never formed correctly. I was surprised with the powder load, they remained almost in the shape of the 7.62x54r cartridge case. Perhaps I need a faster powder??
Lots of blow back BTW as you can see the carbon on the 9 cases.
It's not a faster powder you need, it's higher pressure. I'd use the same powder, but work up to 45.0 grs.
As for the splitting, try annealing the upper half of the cartridge body after you size it, and then again after first firing.




















































