Been toying with a way to use a Form 1 at home. Have been thinking this over for several years and wanted to share it.
Going to manufacture a barrel insert for a 12 gauge single shot 18 inch BBL shotgun, that will slip into the chamber. The adapter will comprise a .45 long colt chamber, a 18 inch long rifled BBL, and a muzzle centering flange that will keep the entire thing lined up. The BBL will be reduced diameter for the portion ahead of the chamber and to right behind the muzzle centering flange at the front end. I'd port the BBL and machine slip-over baffles to stack over the ported BBL and into the inner diameter of the BBL. Methinks this would make a really interesting subsonic carbine. Fit with some decent sights and enjoy. The hard work is going to be milling a slot in the side of the chamber adapter area for the extractor, and making a longer extractor (or a second mechanism actuated by the existing extractor to be the extractor for the new chamber). I have a lathe and a Bridgeport milling machine so it's not going to be a kitchen table and a file sort of process.
Host weapon would be your average every day available by the dozens at any gunstore for $75 used single shot hammer type 12 gauge shotgun of indeterminite origin...
Really, a H&R type 12 gauge would be the ticket here.
Using .45 LC you would have the ability to push a BIG bullet at subsonic speeds. Call it a "quiet thumper". Rimmed cartridge would be easiest to make an extractor as opposed to .45 ACP, etc. If I really want to make a Thumper, I might actually chamber it to .460 S&W, and use 300+ grain lead bullets at about 850 FPS. Hmmm......
Same system would work for many other cartridges. .38 SPL and .22 LR both come to mind.