I decided to take a closer looks at Starscream's gun. In essence, it's pretty cool, but sucks as is. Taking out all the Mech Tech guts left a good shell that I thought could fit over his arm to make a sort of gun-arm. I think it works out pretty well, but that's for you to decide! I think it fits on the right arm, too, but I may have only tried it once or twice. Since the colors are reversed on the right, I prefer the way the purple lines up with the arm purple on the left.