Originally Posted by notorious
That's just going by what he said. It's an AR15 in my eyes.
Kinda sounds like that dude's talking out of his ass.
Unless the upper actually has a 3-stage switch that gives you a full-auto mode at the up position, it's just an AR upper. Besides, an upper is an upper; steel is steel.
I mean I guess I could be talking out of my ass here, but as near as I can tell, there's absolutely no distinction between the upper receiver on an AR and an M4.
Still a badass gun and I guess a SWAT dude would know more than me, but if there's really some high-strength steel on an M4, that would be the first I've heard of it.