This is, maybe, the coolest ray gun ever. One of the eBay auctioneers I follow, ToyTent, put it up for sale and kindly allowed me to post these images.
The Atomic Machine Gun by Ideal was made in the 50’s and fired caps. The box and hand crank are replica, but who cares. This gun just looks soooo awesome.
If you’re interested in the auction you can find it here.