Me too (basic, AIT, & stationed at Ft. Beginning :-( ).

This does not surprise me at all. It’s a huge base, and full of unsavory types; all of the communities around Benning were full of businesses doing just barely legal activities designed to separate young males from their paychecks. And so. Much. Drugs.

For anyone who hasn’t been in the Army, the infantry is where they put you when you’re too dumb to pass the ASFAB - a sort of SAT you take when you enlist. The higher your score, the more options available to you. The infantry are the jarheads of the Army, but with less discipline. Even smart infantry guys are dumb in that they had other options and voluntarily chose 11B. I was one of those, and there were far smarter guys than me in my unit; one guy had gone through seminary school, decided at the end -with the equivalent of a four-year degree - that he didn’t want to be a priest, and had joined the army and chose the infantry. People are messed up. Anyway, Benning is the home of the infantry, and it’s enormous, and full of a lot of guys who were there because they had few other options in life.

IME, crime was pretty rife, maybe less so on the base, but certainly around the base. And while my experience matches your’s WRT the military-grade weapons, these are handguns any civilian could buy. Considering how many went missing, my guess is that there’s a supply sergeant somewhere who was accepting shipments of new weapons and “misplaced” a box, and recorded receiving one less box. Or, maybe it was indeed someone with access to a supply depot full of still-boxed handguns who just walked out with one.

The security you described was absolutely spot-on for issued weapons; my guess is these were stolen from a supply shed somewhere, and that it was months or longer before an inventory turned it up as missing.

only the DoD is allowed to rip off our armed forces

No, it’s about right. The military hardly pays much for the firearm because Sig also got the 9mm ammo contract so Sig makes bank.