They say the freebore for 90's (ISSF reamer has .169) kinda wrecks it for lighter weight bullets. My 7 twist does alright with Frontier 55grn hp factory rounds. Being a cheap SOB, I planned on never buying 90s, which means 8 twist. Then the 88's came out, I ordered a 7, HA HA. I would go 8 unless you want to shoot mainly 90's