Personal experience is that #5's are great, have rolled a number of turkeys at up to 40 yards with 12 gauge/extra full/3" shell, usually don't even flop. The #5's put significantly more shot in the head/neck kill zone than the fewer count in #4's. I use #4's as a follow-up, more range and penetration per pellet, but fewer pellets reduces chance of a good hit. I've needed the #4's once when I mis-gauged distance, measured later to be 60 yards. The turkey rolled, did a "death-flop" and laid still until I stood up, then got up and flew back the way he came: apparently just knocked unconscious. The #4's dropped him, but at about 45 yards where another load of #5's might have also. Longer shots are not something to recommend, only justified with a bird known to be wounded. Hold your shots to 40 yards or hopefully less so you can accurately place a high number of hits in the head and neck, and #5's will have plenty of penetration. #4's in the body may kill at a longer range, but body shots frequently won't allow recovery of what is a pretty tough bird.