I'm no gun expert, but I think of "heavy" or "large caliber" machine guns as .50 caliber. AR-15s, besides being semi-automatic, can be chambered in multiple calibers, I think, but I've not heard of as large as .50 caliber. MSM people and Libs/Progs are so anti-gun and so ignorant of guns at the same time, that one must be skeptical of their accuracy and agenda in just about any story involving guns. It's not a situation I like, but I think it's present reality.