new case trimming ?

[SuperMagnum]

Is it necessary to trim all new cases down to the trim to length even if they are between the trim to and max length before loading them for the first time?

[denton]

You don't have to. But I usually do. Starts everything off nice and uniform.

[Rocky Raab]

It doesn't hurt. The mouths are sometimes a little bit off square, and are almost always sharp. Those that come in bulk are often dented, too.

I trim, chamfer and size all virgin brass. It's really no different than if it were fired.

[Cossack]

It largely depends if you're going to crimp the bullet, then case length uniformity is very important.
I found out the hard way that it's a good idea to size new cases tho. I measured powder into a batch of brand new 45 Colt cases that looked so good and uniform I didn't size them... only to find out that the bullet slipped right into them with handly any force or neck tension.