Hey I’m a to each their own kinda guy. But my philosophy is if you need a pistol get a pistol. Don’t try to turn a rifle into one.
To me it’s like firing a .357 magnum cartridge through a 1-1/2 long barrel. All you’re going to get is a horrendous muzzle flash while achieving the muzzle velocity of a +P .38 Spl. Maybe.
Need a pistol? Buy one. Learn how to use it effectively.
Need a rifle? Buy one. Learn how to use it effectively.
Need a shotgun? Buy one. Learn how to use it effectively.
Put all the rest of the cash into ammunition, Range time, and professional training. Everything else is just silly.
One man’s opinion and it’s worth exactly what you paid for it.
L
There are some pistol caliber carbines where that is a concern - CMMG has a 10mm version, IIRC. However, most of these 9mm ARs have barrels at least as long as would ordinarily be found on a Glock, so I don't see where wasted gunpowder would be an issue.
People generally shoulder these things PDW-style, and since it's legally a pistol, no worries about having an unregistered SBR.
38/.357 in a lever action rifle makes for a good partner to a .357 wheel gun and nice muzzle velocity.