I'd forgotten one of the reasons I migrated here: that was to be able to post explanatory pictures.
Well, to inaugurate the audio-visual aspect of this presentation, a picture of the prop that has been taking all my spare time for almost two months.
This is the Fury Gun (well, actually, this is a picture from a couple days ago, prior to the final touch-up and details...like the sights!) A 1930's Pulp Adventure 45mm double-barreled break-open grenade launcher.
It is a practical prop; largely metal, using some actual gun parts (like the pistol grip and the butt stock). Pressure on the forend unlatches the barrels which pivot open for re-loading. The pistol grip and butt stock can be removed for cleaning or storage. And the entire barrel and breech assembly pushes back on a buffer spring (which was a LOT of work for what turned out to be not that interesting an effect!)
Materials run the gamut; from actual gun parts to 3d printing to steel barrels and 1/8" brass tube making up the receiver and 1" black pipe adding strength to the forend, to details of Apoxie Sculpt and styrene.
The foam plastic grenade is a stand-in. The client who I made it for is making up some rounds out of plastic. I might do a couple myself...once I recover my strength!