re: #228 Sol Berdinowitz
Because, for all practical purposes, there is none
That system is damn hard to control without a foregrip and lots of practice. If you look at the second video, the muzzle is at times moving visibly. Unless your are dealing with a solid mass of targets (which even most mass murderers are not), those unsteady shots are very unlikely to hit something. The people in the first video who can keep the rifle steady handle it as trained people would, and thus are effective with it. That effectiveness takes a long time and lots of money (ammo isn’t cheap) to acquire. A nut bent on going out in blaze of evil isn’t going to be able to master the skills without spending a lot more money and time than such people generally have.
Bump fire is something of a red herring, unless you are dealing with someone far more skilled than any active shooter is liable to be. Unlike actual full-auto, it cannot be effectively used to sweep fire across a wide area without firing multiple short bursts (another discipline and control skill) and firing an AR-15 at that high a rate of fire will overheat the rifle in short order.