The carbine pistol stock is more viable than people think. The problem with most was a poor design with considerable play in most examples EXCEPT the Broomhandle Mauser.
Certain vintage handguns are exempt from the prohibition,being found in collections or arcane calibers.
I owned a C96 commercial in 7.65 with the stock, perhaps the only example that works well.
I took it to Colonel Jeff Coopper's GUNSITE class as a joke, his disdain for small calibers and admiration for the 1911 well known.
After he calmed down, the Col took my broom and proceeded to shoot up a box of fiocchi's at some rather LONG ranges with usefull accuracy and put my few handloaded winchester silvertips into gelatin.
He finished with a undeniable smile and a look of brainstorming some ideas.
Then I pulled out my 3 digit colt navy 1911 and started another lecture about fine fireams.
There is an Arizona sheriff writing for the firearms magazines who carried a 'broom along with his big bore S&W while on horseback for just such an application.
A nearly forgotten firefight between Polish cavalrymen and a Bolshevik unit in the early post ww1 period saw broomhandles VS nagants at close quarters. The polish nearly wiped out the much larger Soviet force.
That little 7.62 was the fastest pistol cartridge until the .357 came out.