I was a MP a while before I went to Vietnam (82nd MP Company, 82 Abn Div) and after I returned (67th MP Company Ft Devins MA). We were issued a loaded mag when we were issued a pistol. We carried the pistol loaded w/empty chamber.
The only time we carried empty guns was in training. I never saw a MP being required to carry empty guns while on duty.
CPT USAR Ret
USAMU Sniper School Oct '78
Distinguished Rifle Badge 1071