.22 gallery guns are a thing of mine and it doesn’t look like any that I recognize. From close examination of the OP’s pictures I have to agree with him. It is clearly pneumatic. There is a very obvious spring loaded BB magazine on the right hand side of the receiver. I thought BB gallery guns shot steel shot so that it could be reused? I don’t know if it was pintle mounted or not but it looks like it was just tethered. Brian, just curious, what leads you to believe it is full auto?Are there any visible markings on it?What is the receiver made of?
I'd guess it is a BB gun given the air nipple/connection sticking on the bottom