I am using copper plated #5 shot , and the load is 1/18 oz of shot over 2 1/2 drams( 70 grains) of FFg powder. I found that the #5 has sufficient pellet energy at 30-35 yards to kill pheasants cleanly out of a cylinder bore gun. Beyond that the patterns get rather thin, and hitting a pheasant becomes problematic. The pellets hold enough energy to kill out to maybe 40 yards, and cripple at 45, but I like to hold my shots to 30-35 yards, if I can.
Read Bob spenser's Black Powder Notebook, both his article, and that by V.M. Starr on shotgun loads for various gauges. Its very educational, and you will probably be surprised that to get better patterns you use LESS powder, and less Velocity than what you might use in a shotgun with chokes.