I recently had a 7 SAUM built and the the free bore is 0.177, attached is the load data that I use. Grains of powder (Retumbo), Berger 180 Gr Hybrid, Olgive to Base, COAL, and velocity, this is out of 7.5 twist 26" Bartlein Carbon Fiber barrel. I found the brass at Powder Valley and Natchez shooter supply. Hope this helps and it is a tack driver, no picks at 700 yds but if its a calm day it will group about 4.5" at 700 yds, and if a real shooter did it I'm sure it would be even tighter.