This is a tool that goes in an ammo slot. Automatically activates whenever the gun starts reloading. Once activated, the player can leave the gun during reload, and it will automatically load the same ammo that was being used rather than defaulting to standard.
Gunners would only have two special ammo types to use if they took this tool, but could more easily run more than one gun.
Engineers and pilots would have no special ammo types, but could keep whatever a fellow crew member had loaded.
AI should all carry this tool by default.