My antelope rifle is a 6RemAI and I use 95gr Nosler at 3400fps in a 1/10 twist barrel it's a pretty good rifle. I also shoot a 243AI with a 1/10 twist barrel with 80gr bullets 3700fps plus and one of these days I might shoot the same bullet in both rifle just to see how they compare in velocity.
Years ago I had a Rem 40x 6Rem with a special order barrel 1/12 twist and the test targets that came with the rifle had two five shot groups in the mid .2' to mid .3's with the old Rem 80 match bullet. I could duplicate the load and groups almost wore the barrel out still have about 500 Rem 80gr match bullets.
I always figure if Rem can build a rifle to shoot like that I sould be able to have one build that can shoot like that. I think maybe the only real difference would be in velocity and it didn't stop me from building a 243AI. I also shoot the 6Rem/243 and my 243 has been rebarreled afew time I got that rifle new in 1965 so for 43 year now it's been 243vs6Rem both of them are good calibers.