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.