To the OP, let me offer a small disclaimer assuming you are new to turkey hunting.
Shooting turkeys at beyond 40 should be reserved for people who have spent considerable time patterning their guns. The downrange killing power of lead drops like a stone at 35-40. Shooting turkeys at 45-50 is no different than flinging a 60 yard shot at a whitetail with a compound bow. Sure, you may make the shot... But there's a darn good chance you'll miss or worse yet end up maiming the turkey.
I appreciate those people that do take the time and become turkey marksmen. I suggest that the better and more ethical route is learning to call them. If you cam get him to 45 there's a solid chance you can get him to 25-30.
The consensus for 12 gauges is a .670-.675 choke when using #5-7 shot. With lead shot #5 is solid, with Hevi-Shot the #6-7 is better. Be wary of the Federal Flight Control loads as they only perform when using a choke without wad catchers.
This post was edited on 10/14 at 8:33 am