Since you wanted it, here it is:
First of all, it's stated from the start that these guys are supposed to be some sort of ex-special forces hardasses, but they really don't act like it. Like, at all. If they were really leaning so hard into their training they wouldn't bother doing obvious shit like warning each other that the fountain water's not safe, or having to make plans on the fly to the extent that they do. For normal soldiers that would honestly be excusable, but if you knew the first thing about special forces you'd know that those guys go nuts for planning missions out. Given that they're even participating, they probably care enough about winning to take it seriously. Their general dialogue also just doesn't really feel at all like how special forces would speak, retired or not. I feel as if you'd get a lot more leeway for yourself if you retconned them to just be retired veterans—maybe look into marine scout snipers for some ideas. If the utility of the dialogue is to explain a few things to the reader, you'd be better off with normal narration.
The whole taking the glasses off thing seems like it could become a pretty serious plothole if left unchecked, but since it's the first day of the challenge I guess it can be excused.
About the AR-15 thing. First of all, why would they even bother? As far as the audience knows, they're supposed to just get across existing civilian territory with highly limited resources, and law and order is still clearly in play. The second someone hears them shooting that damn thing, they're pretty much fucked on principle due to the cops that it'll draw. Even if it's suppressed, leaving bodies behind is also going to get the cops involved sooner or later. And honestly? Why would they bring the damn thing to begin with? There's not going to be many enemies to shoot, they're civilians in friendly territory. Unless, of course, there's a group of hunters that the cops ALSO don't know about, which just raises a ton of questions about the challenge itself(that I'm sure will be explained in due time, to be fair!).
What left me more dumbfounded, however, was the rifle being described as a "Collapsible AR-15". While it's true that collapsible stocks are a common feature on these rifles, the phrasing seems to describe the whole rifle as collapsible which doesn't actually exist, as far as I know. A collapsible stock would also not add much to the portability of such a rifle. Folding AR-15s exist, but that's not what's described here(unless that's what you meant to say? Still poor phrasing, though).