Thanks for the contributions so far, very interesting.
It was the issue of hearing protection in particular that made me suppose there were indeed other firearms than the 1911 involved, but seemingly that was not the case or only in terms of "paper tiger" projects which never actually reached the guys in the mud....
"Get off of my lawn!" Walt Kowalski
. Savage Axis XP (.223 Rem)
. G17 3rd gen. (9mm)
. Taurus PT22 PLY (.22lr)