3/12" or 3' No. 5 Hevishot. Although last year I was not that impressed. Shot a bird left-handed(I'm right) and he ran a good 100 yards before going down. I pulled the shot a little bit but there was 6 holes through his breast and lungs, plus other areas.
I know I did'nt head shoot him, but I was amazed at his willpower. Saw one shot youth season with the same load at 35 yards and hardly kicked, got knocked over and stayed there.
I use 3.5 inch no 5 from Kent. If you hit them in the chest the feathers are so thick that you will not get good penetration, also the heart and lungs are lower in the turkey and not right up on the breast bone. You definitely want to aim for the hears and neck for sure killing shots.