i have a 21 on my remington 870 express mag turkey gun.....i love it...i hunt long and hard.....and like to have my gun on my knee ready...just me.....i have a mossberg 500 with a...26 or 28 on it......good gun...but heavy and the long barrel gets in the way walking in the woods and swinging the gun once in a while.........ultimag is right.....that a shorter barrel doesnt reach its highest potential velocity.....takes something like 28 in a shotgun?? not sure......but its NOT that big of a diffrence.....think its like 10-20fps an inch if that.........and thats not much of a diffrence in a turkey load.....dont tell the turkey i rolled at about 35-40yds from a 21 inch barrel that my shot could have been going faster!........IMO buy what feels right and you like....some guys like longer barrels......i like my 28s for wing shooting.....but i got my turkey gun solely for hunting turkeys.....its all upto you in the end.......thats really not one better then the other.......and my 21 inch barrel in my rem with a undertaker HS tube and a 3 inch rem high velocity 1 1/2oz 3inch mag of hevi-shot #6's puts something like 190 pellets in a target at 30yds......the gun is feather light...and believe it or not it doesnt kick all that much even with a stiff 3inch mag......dont ask why.....i mean..im not tooting my own horn but i am decint sized and been shooting all my life..and take recoil well...but i really dont think its bad......i like to pattern my turkey gun lol....good luck......and dont let someone try to talk you out of a mossberg....they are EXCELLENT guns for the money......i cant count the rounds i put through my 500.....and weather condition...any season.....always went bang.....and put the pellets where i wanted em......good gun....i know theres guys out there that may try to tell you something else is better blah blah.....mossbergs are cheap and crapy......they shot good and are rather cheap......i only went with a remington because thats what dad bought me for my birthday....but i do love it.....i like it because its so small.....the mossberg has bulk to the stocks and reciever....my rem is alot thinner....