Straight wall cases stretch very little to nothing at all. I will trim revolver brass once, never had to trim it again. I once trimmed hundreds of 45 ACP cases, chasing best accuracy for USPSA competition loads. I don't think I really gained anything in that effort and all the brass was eventually lost in matches. In big matches, you were not allowed to police your brass, that was payment for the services of the range officers.


Bottle neck cases are a different story. Typically, the case neck will stretch as the case comes out of the die, the expander ball swages the case neck against the die and that will stretch the brass.

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VCDL, GOA, NRA