There are documented cases of people being hit with all manner of small arms rounds that kept on fighting. Again, it all depends on the condition of the human who is hit. His mental attitude about being shot, his state of sobriety, use of drugs, and even just religious fervor all can make a man take incredible amount of abuse before he ceases to fight.
Right now, the only firearm that seems to be able to put a man down fairly ocnsistently is a 12 gauge shooting slugs. But that is not a handgun. The new 50 caliber revolver cartridges have not yet been around long enough to be tested in real combat, so the jury is out. You have noted the trouble handling the recoil when shooting them. Its hard to believe anyone can shoot this accurately enough without a flinch developing so that it can be used in a combat situation.
The .357 shooting 125 grain jacketed Hollow Points has the best one shot stop record for handgun cartridges, with a torso hit. It even edges the heavier .44s, and .45s. Go figure?? I still can't find and volunteers for testing. :surrender:
The one black powder handgun that had a pretty good track record for stopping a man was the old Tower Flintlock pistol, in .62 caliber. With a round ball weighing 3/4 oz, and traveling at modest velocities, any torso hit would usually take a man off his horse. And that is from historical records from the British, and comments made by American historians after observing the pistol's use in shipboard fights, and in land battles. The pistols were smoothbores, with either a front bead, or no sights at all. They were heavy, and usually carried in saddle scabbards, hung over the horn of the saddle, in pairs. They were " point and shoot " weapons, and were used in conjunction with swords by cavalry troops, or " dragoons."
They were far too long, and heavy to be carried on a belt, so never found much favor with the walking public, who wanted a pistol for self defense, but had to resort to small calibers, and smaller guns.
The famous .41 Colt Deringer was a notorious killer because the bullets were outside lubricated, and the grease held onto all manner of pocket lint, and debris, which was pushed into the wound along with the bullet. The bullet could sometimes be removed, but the lint and debris caused a slow, painful death from peritonitis, because there were no antibiotics. The round also was so weak, that is could not send the ball completely through a man's body with any kind of a torso hit, so that a man facing someone holding a deringer was pretty assured that if the gun fired in his direction, and he took a bullet, he was going to die. That probably deterred more bad guys from pushing a gunfight, than all the other guns used in the American West. The little gun did not deliver a " punch ", or knock anyone down, unless a brain shot was taken across a card table, but its reputation for a mean dying gave it respect far beyond it mechanical and ballistics capabilities.