I'm an older guy, I was in Berlin in 1961 and all of my senior NCO's were WW2 vets. Actually folks I don't think anyone was legally able to bring back taxpayer purchased military equipment. They were able to bring back registered war trophy's. The unit S-3 office had all the paperwork. A fairly substantial number of guys, mostly from National Guard units like the 29th Inf Div were able to take a certain number of weapons as long as they weren't assigned to that unit. (read battle field pick ups of M-1.s etc that weren't on the unit's property books) I hate to say it guys but read stolen into that.
But, the NRA and the old DCM began to sell 03's, M-1's, and Carbines, and yes even Johnson rifles to eligible vets.
Handguns also. In 1960 the first month I was in Berlin I went to the Rod and Gun Club and bought a 1911 for $16 bucks, WW2 Air Force issue Smith M and P for $5.00, and a German PPK that had been tossed into Lake Wansee and later retrieved with about 2K of the others. The German gunsmith at the Rod and Gun restored at least 50 of them and sold them to us for $2. bucks apiece.
Ah the good old days. But no freebies that I ever heard of, Uncle Sam is a bit nitpicky on anything on a property book.
I think the problem is that so few folks nowadays have ever served and are unfamiliar with military law. So if Grandpa says "I brought it back from the dark recesses of the earth," most likely means he got it from DCM at a really cheap price.