I think there is a lot of back and forth going on about it, so let me clarify my complaint. It's not that the AI loads ammo. It's the fact that its a full clip already and doesn't need to be reloaded in the first place. So it doesn't matter what the AI loads into it, it's that if a player loads ammo they want to be ready when they shoot it, they shouldn't have to worry that the AI is going to run over there and reload an already full clip on them.
I mean, I obviously don't expect a human engi to have all the same ammo I do if there are multiple guns on the ship, so I don't mind if after all the shooting it's different ammo type. What annoys me is that there are no enemy, no shooting, and therefor no reason to change my preloaded ammo to begin with (I've thrown people overboard for touching my guns in such a terrible way). The difference is that usually after I tell a human engi 'hey, please don't change my ammo if it's full' they listen. I've tried with AI (and they are terrible at conversation. I end up talking to myself and get glanced at by the remaining crew. Thankfully they don't argue, being I'm the one at the gun).
I wouldn't know if its a bug or not (I have very little knowledge of coding, I'd have to ask Alistair since he used to do that for a living. It feels like a bug, but I wouldn't know), but honestly it doesn't matter. It's simply an annoying and sometimes hampering happenstance, especially if you are a gunner with a lot of different guns that require different ammo to be ready at a moments notice.