My son relates this story from his time in Iraq in 2006 and 2007. He was an army tank crewman but for the last few months his platoon was attached to a Marine Corps unit I think somewhere near Ramadi. Before that they were at Tal-afar. The marines, when they left the post or base to go an a mission, would only load their weapons after actually leaving the post and on one instance, received fire when they were doing that. I don't recall what he said happened next.
For my part, I once did guard duty when still in AIT at Ft. Sill, Oklahoma, with an M14, the only rifle I ever saw when I was in the army. It was loaded with three rounds but there was virtually no instruction (that I recall) about what to do when. We guarded the artillery park.
Shoot low, sheriff. They're riding Shetlands!
Underneath the starry flag, civilize 'em with a Krag,
and return us to our own beloved homes!
Buy War Bonds.