When I was an SP stationed in San Antonio at Kelly AFB we use to have to take a bus to the Lackland AFB firing range because we didn't have our own. We use to joke about how it would be funny if someone tried to "carjack" a busload of M16 wielding SPs
Actually that joke is what changed our SOP of waiting to get ammo at the range...we were transporting 40+ M16s and 9mm Berettas and no ammo to secure the weapons even though we were travelling off base to go to another base. Our base commander was concerned about military LE carrying loaded weapons into civilian areas and it being a Posse Comititus issue. When we said that if someone learned of our "no ammo policy while transporting" then it could be a real possibility of being robbed for our weapons and just think of how embarressing that would be!!
He quickly saw our point and said that since we were armed all the time on duty then it wouldn't be a big deal if we had ammo while going to another base...What a genius