I have the first year Remington mad the 870 super mag. This gun patterns great but is heavy. Remington has a 870 predator/turkey model now that has a 20 inch barrel and shoots 3 1/2 inch shells. Would that short barrel in theory pattern with a 3 1/2 shell the same as my gun now. I guess what im asking is will all the powder in a 3 1/2 inch shell burn in a 20 inch barrel or will some not be used?? Does that make any sense?? lol Like I need a new gun but boy that would be handy in the woods.