The thing I am most curious about is the barrel. I've seen a choke shaped like that, but it wouldn't affect anything because the straight or parallel portion of the barrel would already be driving the shot in a straight enough line that it wouldn't open up. In a blunderbuss, the barrel starts to widen much earlier on. This would of course reduce velocity considerably, but there is a diminishing point of returns on that inside the house anyway. We know it's a myth that you just have to point a shotgun in a defensive application because the spread is not wide at all. Moreover, shotguns loaded with 00 buck penetrate a lot, something like 13-14 sheets of drywall (or 6-7 walls). When you look around most peoples homes, you can see the danger of over penetration for both your home and that of neighbors. It would seem to me that this technology could work again to make it harder to miss indoors while reducing the ability to overpenetrate.