1960's Colonel Wesson took elk, grizz with 357 swc's
Now this was an 8" barreled Smith, with the full load 160 gr swc, at 1550 fps. Charley Askins, ever the naysayer, said that the critters were small and unimpressive. I don't recall seeing any info on their size/wt. But Lewis and Clark took elk, bison and grizz with Ky rifles, which don't provide any better performance. Elgin gates took a Cape Buffalo with a 357, but IIRC, that was with a brain shot. Ted Nugent has supposedly taken a Cape Buff with a 10mm auto, utilizing a spine hit. I wonder fi that was from a tree stand? Bill Cody supposedly took Bison with a .44 Russian revolver, but that was by means oif shooting them in the ear hole, again, IIRC while riding alongside of them on a horse. The revolver was supposedly chosen rather than being limited to a single shot rifle.
When I was in Rhodesia, 1977, I was introduced to a man who had taken 3 Cape buffs with a 357 and an elephant with a .44. Since it's illegal to hunt dangerous game without a pro hunter present, you can bet that an elephant rifle was being aimed at the critter as the client shot it with his pistol! :-). Water buffalo are "commanded" all over Asia with nothing more than a stick, guys. Very few animals charge after being shot. The natives poach elephant with AK's, you know. It's been filmed for TV. They simply stalk to within 10m, fire a full auto burst into one lung, and run like hell. They then wait 24 hours and look for circling buzzards.
Larry Kelly, he of Magnaport fame, said that he took a tusker with a .44 mag, too. So there is no reason to believe that a hot .45 L colt can't handle Cape Buff just fine, actually. When you put a 1/2" diameter hole thru both lungs, that critter is a goner in a minute or two. Its demise is faster if there is an exit wound, to cause collapse of the lungs. The exit wound also produces a more reliable blood trail. The skin of the critter shifts over the entrance wound, quite often, and that means little or no blood trail.