BTW, that nut job in Colorado did all his damage with a shotgun loaded with 00 buck.
His AR jammed
Not to encourage other nutjobs, but my take on that AR jamming is:
1-he bought a new AR
2- He didn’t clean it after he bought it and clean it before he used it
3- He didn’t break it in.
4- He didn’t learn how to clear stoppages fast.