I havent gotten around to buying a 500 smith and wesson yet but want one for Grizzly Bear defense. What are the differences in velocity for the different barrel lengths? I want to be able to control it and get enought velocity for the big round. I also want to be able to carry it on the belt. Who makes holsters for these? Considering between 3 and 14 inches... How much muzzle vel does this have? Is it close to a 3030 or 12 guage?