The size shot I use is #4 buckshot. I would pattern your loads no matter what. Maybe if you had a 3 1/2" 12ga you could consistantly get coyotes at 70 yards but at close range you pattern would be very small. You would need more than a bead on the end of the barrel for a sight. A standard 12ga #4 buck shell (2 3/4") has 27 pellets. A full choke pattern at 10yds is 10" in diameter (90% of the pellets). A full choke pattern at 70yds would be approximately 70" across and not a consistant coyote killer without a lot of shot. I think a 70 yds coyote killing patten would be too small at close range to cause misses on a runner. If they are 70 yds away, that's rifle range.