What cartridge would be the most efficient short barrel giving me the most velocity. I’m running 20” 6x6.8 w/55-58s for day time. I’m using 6x45 18” w/70s going almost 3000 for night. I’m hoping to possibly shoot a 70 in a short barrel 6x6.8 or similar to achieve similar results to my 6x45 18”. Should I pick a 6.8 To shoot 70s? Maybe 11-14” barrel. It will be a atv/truck gun/night gun or woods large predator calling gun. Washington won’t let me run around with a mag in the rifle with a vehicle unless it’s a pistol.