I am relatively new to reloading. Have a new case trimmer on the way. I measured a bunch of cases with my cool new micrometer. Many were a good bit under the trim-to length in the manuals (several different calibers).

The way I understand it, there are accuracy benefits to be had from having uniform case length. So should I trim all cases to the length of the short one, so they're all the same? Or should I just trim the long ones and let the short ones grow a bit?

Any other tips for a newbie trimmer would be welcome.

Presuming you're talking about the short length in just one cartridge group, that's what you should trim to. Also, don't trim new brass until it's been fired once. You'll find the brass will great disparity after shooting and require uniforming and trimming again after fire forming.

Anything which will make ALL your brass virtually identical to each other, won't hurt.

Do your trimming after you resize...the resize process will change your case length.

Ok:

-New brass, fire once first, then trim.
-Resize/decap before trimming.
-OK to trim a batch of cases to the length of the shortest case, for uniformity, even if the short case is up to .010 shorter than the "trim-to" length. (Right?)

Great tips. Any others?

I like the lead plugs Sinclair sells that help determine the exact length of your chamber. Basically, you sacrifice a case by trimming/cutting off .100 or so, insert the plug in to the case mouth and chamber the round. Then carefully remove it and measure the overall length. I do this a minimum of three times to make sure the length is consistent. The last factory chamber I measured was .020 longer than SAAMI specs. With this rifle I won't need to trim cases for awhile!!!

Good Shooting,
Ben H

Ben H
Most chambers are cut longer than SAAMI specs in this area.

Still,there are benefits to having all of your brass the same length.

The only really accurate trim die is a file trim die IMO....The lathe types vari a good deal, but not enough to make a lot of difference in accruacy IMO..Mostly triming is for safty IMO....

I only use a file trim die for big bores wherein I need real repeatability to get the proper crimp in the cannalure on certain calibers...