Hi Phil. Barrel length is not critical for knockdown performance, that is more dependent on your choke. I personally like short barrels for fast handling, say 18 to 22 inches. But some others go with a 26 inch barrel. A longer/ heavier barrel will help to counter some of the recoil, an important consideration when you are shooting a pump gun. With magazine capacity, more is better, 5 rounds will put you in the game.