Trim Length for 6.5mm BRM and Other BrassThere are two reasons to trim your brass: First is just to make sure it's not too long for your chamber. But second, is to even them all up to the same length for accuracy considerations.
1. A Chamber Diagram (left) will tell you the maximum length. If everything measures shorter than that, you shouldn't have to trim unless you want to even them all up. Chamber diagrams for most cartridges are listed at the ammoguide.com website.
2. How to Choose an "Even-Them-Up" Length - Quite simply, measure the length of each fired case and determine which one is the shortest. Then, just trim them all to match that shortest one.
Uniform case lengths improve the consistency of bullet align-ment, exit gas pressure as the bullet leaves the case, and bullet retention friction in the case neck. If you haven't got a case trimmer, we recommend the Forster Original Case Trimmer...
It's the easiest and most versatile case trimmer available.
6.5 BRM Chamber Diagram Courtesy of AmmoGuide.Com