Hi kiwijames, I've fireformed quite a few cases for my 300Lapua improved. I use N320 from my pistol shooting days and oat bran from supermarket with a patch to plug the end. Work up from a lite load something like 10gn in .243 till you get the case forming out fully. Just finished 50 cases for my 338-416 but it took 27gn to fully form the brass and had less than a .001 run out in the necks.
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