As to why bother, when you can nearly get 325grs going nearly as fast in a Ruger .45 SA, and certainly get there with some other caliber revolvers, what you will not get on arrival or even after impact, is .61 cal.

Neither will you get, even with a pump gun, the pure menace of a shorty double. I own a Shockwave 12ga 14.5" bbl, and it weighs about a pound more, and is about 9" longer, to get the 3 extra shots. Since I carry a gun a whole lot more than shoot one in life and death scenarios in civilian life, two shots of 20 ga is just fine, and if i need more, there is always the G43 9mm somewhere on my person.

of course, also the obvious, in many/most states, the gun mailed or bought over the counter with no more paperwork than a bill of sale, and ditto many/most states zero record keeping, or it even called a firearm and may as well be an umbrella. But, again, CHECK for your area and KNOW.