Necked Down .40 actuallyThat’s practically a .357SIG. I know, slightly larger diameter bullet, but it is essentially a necked down 10mm, and they DO offer conversion barrels.
Yes I‘m very familiar with the 357sig, I’ve had most of the makes and model handguns chambered in that caliber and still have some.
7.62x22 would be even faster and lighter recoil and better penetration than typical 125gr 357sig, those would be the advantages.
Of course someone may point out “do you want handguns banned, because that’s how you get handguns banned” lol