"IMC Armories: exploits related to clipping through the roof, a mantling bug after teleporting in, and various script errors." This was supposed to cover all the possible bugs around the armories. Players had found different ways to sneak into the armory. All of them seem to be patched except for one.
Granted the most dangerous ones were the ability to throw grenades into the closed space and use an Ash teleport to shift in. Those don't work anymore, but players can use the Trident to shift one player in at least. If you can get the trident on the top of the Armory, if you stand underneath the trident, and another player hops in the driver seat, you should phase the bottom player into the armory.
Again, this isn't exactly ideal, as the one player is left in there alone against three possible enemies. You could use an Ash teleport or Wraith ultimate to bring in your teammates, but it isn't exactly foolproof.
Try it for fun, but don't be surprised if it fails miserably.