6mm ARC, you have plenty of bullet choices from 58gn to 115gn. it is a very versatile round from range plinking and prairie dog, deer, hogs. It is also pretty cheap to reload, maybe a few pennies more than reloading .223, and has ballistics that out do .308 by a slight margin. stays subsonic out past 1200 yards with some of the secant olgive bullets in the 105 to 110gn. And you can get 3000+fps with the under 100gn bullets.