Help remembering another fps

I think weasel posted a vid on it before, but it was some experimental fps that gave you a pistol that was quite interactable; I remember watching the way you have to check your ammo in the gun by popping out the mag and looking at the notches in the clip. I think the primary enemies in the games were these flying robots, similar to manhacks but with guns.

Receiver?

Yeah, thank you!