Shotguns are not a novel concept, and haven't been for hundreds of years. A few inches size difference, and even the change in loading mechanism, do not appreciably detract from the core function which remains pretty much the same. To attempt to draw a line between the two re:RKBA is to expose a bias that will not be satisfied by any examples or words, instead passionately seeking out any variance upon which to hang the "because of X, you can't exercise that right" argument.