I've heard rumors that later PPU brass wasn't annealed, either, and splits when trying to fireform it to K-Hornet. (I shoot a stock Hornet, so it doesn't matter to me, but I thought others might find it helpful). The older PPU brass is pretty good stuff, or so I'm told. I've only bought one box of it, and still haven't tried loading it yet. I've still got about 40 rounds to shoot up before I endeavor that chore.
I fireformed 400 factory PRVI 22 Hornet cases to K-Hornet and lost a few to split necks - it's been a few years but want to say it was 3-5% loss. Prior to that, I loaded new PRVI Hornet brass to fireform and lost closer to 10%, FWIW...
