[marktwain]

I don’t know why you couldn’t take a old 22cal barrel and ream out the rifling, except the chamber, and put a ‘jug choke’ in the end?

A ‘jug choke’ can make a CYL bore shoot a tighter pattern.

I think it would work. A fair amount of effort.

I don't think you need to ream out the whole bore. The experiment indicates the choke overcomes the rifling effect.

More experiments are ongoing.

I could see barrels that are rifled for 12 inches, and smoothbore, at a larger caliber, say .38 for 12 inches, with a choke on the end, that would shoot both bullets and shot well.

[Oatka]

The experiment indicates the choke overcomes the rifling effect.
Taurus successfully uses this in the Circuit Judge carbine.