“civilian guns are strictly prohibited on military bases.”
In my day they were stored in the armory if you lived in the barracks on post.....living off-post with them was a different matter, but even then, you could elect to store them in your units armory if you wished
As a Marine, back when, we never had weapons unless we were involved in direct training. The weapons were issued out of the armory!
Actually personal weapons can be held on most bases and besides that most bases right now only check your id and eyeball the vehicle passengers. If you are in an expected delivery or some other service vehicle they won’t normally do an extensive check but that might change depending on these circumstances.
Pretty much the way it's still done. But of course the point is that the soliders are generally disarmed, except when on the range or training/exercise area. Not only the soliders, but us civilians too, Army and contractors alike. Many of the folks I work with have CHLs, but we can't even take our handguns onto post and lock them up in our vehicles so we could protect ourselves and others once we get back off post.