C&R handguns are exempt from the SBR rule, if they were originally fitted for a shoulder stock. Guns like Mauser Broomhandles, the rare Webleys cut for the stock, Hi-Powers, etc. are fine.

That doesn't help with this question, just some info to further muddy the waters

I have wanted a Ruger Super Redhawk .44 Mag revolving carbine for a while now........it seems an ideal solution, if Ruger could make me a 20" barrel (might as well go longer than 16") I could have a custom shop like Pinnacle fit it........and then have a custom stockmaker fit a shoulder stock. The grip "peg" of the Super Redhawk would allow for the stock to be fitted to the gun far easier than having a S&W fitted for one.

To avoid the "burn" on your hand, you would need a two hand hold back on the grip of the stock.........there have been numerous attempts at revolving carbines and stocked revolvers, none of which were ever really successful. Colt tried a revolving rifle, Remington tried an 1858 Carbine, and all the military Colt cap and ball revolvers had an option for a shoulder stock, but I doubt many were used with these stocks.

Taurus is trying it now with that Circuit Judge thing, but I will not buy any more Taurus'.