Having a high regard for precision, I trim. Brass for 10mm average .988" Cartridges used for the highest level of precision shots need sorted by length and by mass and trimmed to the same length to ensure concentricity of the rim - This cartridge headspaces on the rim, so case length must be right to ensure the C.O.A.L. positions the ogive of the bullet to meet the "sweet spot" distances from the lands.
I do believe this is one of most important methods to get low standard deviations of velocity, and therefore tighter groups vs. not trimming.
"What's the down side to 10mm again? Oh, that's right, there isn't one."" Carrier21
Last edited by Kegs; 12-27-2010 at 08:14..