I've gone back and forth on a new AWB. I've fired various assault rifles, they're deadly in that they are
ridiculously easy to use/aim. It felt like I had auto-aim on in a video game. That said, as mentioned in this thread, the overwhelming amount of gun deaths and injuries are caused by hand guns, not rifles. And the reason for the high kill count was not just the gun used, but the size of the magazines, which is not an exclusive thing to rifles (there are high capacity magazines for pistols and shotguns).
To me, rifles make sense for hunting, shotguns for home defense (at least, more than rifles or handguns - you're still more likely to do harm than good with a gun at home), and handguns only for recreational or competitive target shooting. All make sense for collecting, sure. But the two things that don't make any sense are high capacity magazines of any kind, along with ammo stockpiling.
You don't need hundreds of rounds at home. You don't need a dozen 30-round magazines. Banning and recovering those would make a much bigger impact on mass shootings than just banning semi automatic rifles.
Banning both open and concealed carry for handguns (only usable at the range) would also help, but that's not happening for at least a couple more administrations...
It's not really even close to being based of the AR-15 platform though, it's closer to an AK in terms of operation, it just uses the AR mags(like every other carbine length rifle made in the west) and ergonomics.
Sigs are a pretty rare choice for a terrorist nutjob though cause they are a good 2-3x the price of your average entry level AR or AK.
Money doesn't really matter when you're about to die.