finding the right powder for the barrel is always the first hurdle for me. I had a 26" Critrerion in .260 Rem that loved H4831SC and 140 grain SMK. Anywhere between 44.0 - 44.6 grains flat velocity and consistent sub .5 MOA performance. Replaced it at about 2500 rounds with a 30 inch Shilen. That barrel hates H4831 but loves H4350, I have a 24 inch Criterion in .260 on another gun that has never met a powder it did not like
once past that I think seating depth plays with the group sizing a lot
once past that I think seating depth plays with the group sizing a lot
