Orwell wrote: The fellow you met with the 14.5" "Mk18" may, indeed, have just had an M4....."Army stuffs"
errm while under normal circumstances that may be fine and dandy logic, you know for Joe Schmoe Navy/Army/Cream Corn like in your example, but this guys is a marksman for Team 2 I'm pretty sure he knew exactly what he was using, do look at my location and what I said I was doing, I didn't wheel and deal to the blunt end.
Most of the Team guys I know can't tell you what their kit is beyond plate carrier or a "Rhodesian", but they can tell you just about anything you want to know about their weapons, I also know this guy personally and have no reason to doubt what he says to me.