My Lyman 49th manual calls the trim to length of 9mm Luger at .751" but many of my once fired Winchester and Blazer cases are measuring in at .743" and up. The manual says "The cartridge headspaces from the mouth and therefor case trimming must be uniform and accurate. Do not reduce cases below the trim to length." Are there any inherent issues with the shorter cases? I am new to pistol reloading and trying to learn.
Thanks

Mals