Hard rubber stunt rifle seen hanging on the wall in the UAC weapons lab. This gun seems to have been cast directly off a hero gun that never made it into the movie. It looks very similar to Sarge's gun so it's often been called Sarge's prototype. One theory is that it was actually Duke's gun but it looked too much like Sarge's so they gave him one of Portman's spares to use during filming. Some of the prop documentation in the weapons lab refers to it as the AGK-310.