one thing that everybody around here seems to be missing, the 20 ga. was made to shoot a 3/4 oz load and any increase wt. of shot from that amount just makes the pattern a little worse. that's the law of physics caused by the roundness of the pellets and the bore. some gauge's are more particular than others, some just don't care. trial and error is the only way but don't think you will ever get a tighter nicer pattern shooting more shot than less, not with the 20 ga. anyway. there may be other reasons to go heavier but a nice even pattern won't be one of them turkey don't really care what they get hit with, use something and get close, try hunting

cheers