As this Howdah is a smoothbore, couldn't any suitable shotgun be made into a similar "Howdah" pistol? The old "sawnoff" given some class? Assuming it can be done legally.

I wonder how 12 gauge slubs or brenneckes would perform in such a short barrel? And would the recoil be usuable? A 16 gauge or a 20 gauge?

It used to be possible to buy old 12 gauge shotguns in the shorter chambering cheaply - 2 5/8" (?), from $200 to $400. Because most people wanted the usual chamber length of 2 3/4". I haven't seen many of these cheaper vintage shotguns for some time though, so perhaps have 'dried up'. One with hammers might make a suitable donor gun to be chopped up.

I actually have two hammer shotguns with the shorter length already. Both "grandfather" shotguns. One is a Hollis with "twist weld" barrels and rusted and not up to ti. The other is a Stevens, also with a hammer, the other hammer is broken and missing. My Uncle still has not found it, or did and misplaced it again! A new one needs to be made. However I won't be chopping up either of these.

An Italian brand of 12 gauge ammo is 2 5/8" and I bought a carton or two of these for use in them. Still have some left. Hopefully still available.