First off. Is the shooter a good shot with a pistol?
Me? I have no use for a SB pistol or SB long gun for that matter.
Also a longer barrel (sight radius) will make it easier to hit things. Short barrels are OK but harder to shoot well.
This is a 50 yard group with a rifled 50 cal GM barrel shot using my left eye
. I think the 22 twist is too fast and would rather have 48" for pistols or rifles in 50 cal and even 54.
Also note that a 66 or 70" twist 54 barrel 9" long will shoot into 2" at 25 yards but may take a good charge of powder to shoot well and will still shoot bird shot pretty well at short ranges, 10-15 yards, if enough shot is put in. I have killed rattle snakes with my rifle's ramrod I sure as heck am not going to shoot one when I am hunting.
Grouse I can shoot with a round ball, or used to, I think Montana changed the law. I guess the bird hunters did not consider shooting grouse with a pistol sporting. But I don't shoot things for "sport".
So far as self-defense and clearing doorways? I have better things for this.
Dan