I think that what many are getting at, but are unable to articulate due to a lack of knowledge, is the AR/modern sporting rifle's capability to be outfitted with high capacity magazines that can be quickly exchanged when empty. I have nothing against the firepower of the AR itself, although I have some reservations about what a person's actual motivations are to buy one over a standard .308 or .30-06 (outside of affordability concerns). I hinted in another thread that I suspect the AR has more of an appeal to those looking for some sort of validation of their manhood, but you could say the same thing of some motorcycles, Corvettes, etc. I admit it is not entirely fair to assume this, as well as being kind of irrelevant. Just something to think about.
But you have to at least tacitly admit that the speed with which an AR's magazines can be exchanged, combined with the fact that 30 round (or more) magazines are legal in the majority of the states, is ideal for someone seeking to inflict mass casualties. I'd like to hear what you think about keeping the modern sporting rifles as they are, while having a 10 or 15 round magazine limit, for all firearms. I don't think this would neuter the weapon's effectiveness in home invasion/defense scenarios, but it would make it much less lethal in an active shooter scenario. I think it would be wise to also mechanically add an extra step when equipping a magazine, such as a key or latch. It would do nothing to inhibit the rifle's utility for home defense or hunting, but it sure would make it more difficult to mow down a large number of people with only one weapon. A responsible gun owner would already have his or her weapons under lock and key at home, so the weapon could safely be kept loaded and ready for self defense.