Question for you reloading fanatics that carry things out to the n’th degree. I’ll just explain my situation because I know these numbers. I am reloading 7mm WSM AI.
Spec’s say case length 2.100” trim to 2.090” after fire forming it seems that my cases are getting shorter 2.085” – 2.086” and I see that the end of the case neck is not running perpendicular to the centerline of the case, they can vary 0.003” to 0.004”. I know the importance of having the barrel crown perpendicular to the centerline of the bore so for the best accuracy would it be better to trim the cases so the neck end is perpendicular to the center line of the case? That would bring the OAL down to around 2.080” and about 0.020” back from book spec. My chamber ream measured 2.113” in total putting me back around 0.033” from the chamber dimensions. I know the 7mm WSM doesn’t have that much bullet to case bearing surface anyway so the real question is: for accuracy is it better to have the case neck trimmed for perpendicularity and a straight bullet release or to have this uneven but fit the chamber better and more bullet contact surface area?
Thanks
Bill

You fireformed and the case expanded brass has to come from somewhere so the neck got shorter. 2.08 vs 2.09 will make no difference. I simply find the shortest piece of brass cut it square and cut the rest to match.

I would trim the brass and even out the case mouth. From time to time I trim under book length, and I've never had an issue with it.

Thanks !! Thats kind of what I thought but I am new to this reloading for accuracy after finishing my first custom bench rifle and it never hurts to ask thoes who have been there & done that.
Bill

Some people do agonize over getting case mouths square; I'm not one of them. A lot of things are going on in the chamber that have no relationship to what happens on bullet exit.

First, the case wall and neck is probably pressed hard against the chamber even before the bullet heel exits the case mouth, meaning all any tiny out of square fit would simply be a part of the chamber so far as the bullet is concerned.

Second, the start pressure is so strong and the bullet's inertia is so great by the time it moves a small fraction of an inch it's very doubtful the bullet's alignment could possibly be significantly changed when it passes the case mouth.