I couldnt find any Mauzer brass out here in the boonies, and NO, They do not need to be fireformed, Cast Bullet Kid is right, I tried trimming them first, and then found that it was easier to run them through the die, then I use a pumbers tubing cutter and take off about 3/8". This inadvertently crimps the mouth some, so they need to go through the die again, then just trim to length as normal, I use a Lee Universal chuck in my drill press or a regular drill. I would love to find a 'file proof case trimmer' for 8mm. If you cut some of the necks a hair short, it isnt a problem, the brass will grow anyway.