Re: .243 cal. 1--12 twist barrel
I have a 12 twist .243AI. It shoots the 70gr TNT and the 75gr VMax great with tiny groups.
If you are shooting long range, then the 105 or 115gr would be better with the 8 twist. If you are shooting 500 yards and under at dogs, then the effect of the small bullet is great and the rifle shoots like a laser.
Hope this helps