Re: .308 2.005" to 2.015". Different length & velocity
I’m no expert on internal ballistics but my guess would be that the trim to length has no effect on the velocity. As long as you seat to the same depth every time the actual length of the neck of the case has no effect on case capacity once the bullet is seated. In my mind all that matters is how much usable case capacity there is once the bullet is seated and how much of that space is filled by the powder, where the neck and bullet bearing surface meet is unusable space. The neck tension may be slightly less on cases with shorter necks but as long as you still have sufficient neck tension to hold the bullet in place that should not make a difference.
As I said though I am no expert on the matter, only offering my opinion, hopefully someone will come along and confirm or deny what I have said.
