As long as the powder fully burns why not use a short barrel. The only difference is the sighting plane, you are more accurate with the longer sighting plane but there is no difference in pattern at a given range based on barrel length, as long as the choke is the same. I love short barrels for upland that is why I got the turkey version of the 870 with 23" barrel. The ducks and geese don't know the difference either. The only thing I would wonder is how long of a barrel you would need with shotgun powder to fully burn the powder and maximize velocity, I have heard 18" but I am not sure on that one.