When the most popular gun becomes the civilian version of the new XM5 the Army is switching to you'll understand what I mean, and why outlawing the AR makes no sense.
The typical AR has about half the impact force of most hunting rifles.
It's great for shooting small game if you don't have to do a lot of walking, and awesome for target shooting since you're stationary and the rounds are small.
A handgun would be far more deadly in a school shooting, and an XM5 (or even semi auto 30-06 like the M1 Garand) would be unspeakably devastating.
Outlaw the AR15 and that's what will likely take it's place. Carnage on a whole new level. Watch the video I posted above with the watermelons to understand what I mean.
It's critical we start identifying these troubled people much sooner and eliminating the risk.