new case trimming ?

[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.