He developed 1100fps loads with the RCBS 285 grain SAA SWC.
Around 39 years ago, after a few years experimenting with 250/265gr jscketed slugs in the 12-1300fps range in my Ruger (new model) Blackhawk 7.5".
Then I settled on a load with a hard cast 250gr swc at 1100fps. I've been shooting nothing but that load out of that gun for decades, and before "the glorious result of a mis-spent youth" took its toll, I could regularly ring the 200yd gong on the rifle range, off hand, one handed. I'm pretty confident in the load doing every job I would ask it to do. A bit less confident (today) of my ability to hit the vitals of a charging bear outside of point blank range, though.
IF the goal is to stop a charging ..anything, really.. then you're probably better off with what I would call an express rifle. Or a 12ga with good slugs. Or a brace of howdah pistols...a .50 BMG would give me a warm fuzzy, but only if someone else was carrying it, or driving what it was mounted on.
There are cases of attacking black bears being killed with 9mm Luger and up. There was one case of a grizzly being killed by a bowhunter STABBING it repeatedly with one of his broadhead arrows. He was horribly injured, but survived.
On the other side of the coin, I have seen pictures of the leg bones, sneaker and a fired empty .38 snubnose. of a hiker. (Grizz did it NOT black bear, and that particular grizz was later stopped with several rounds of 7mm Magnum)
Also there is the story of the guy who carried a .32 auto as his bear defense gun. When asked by a buddy how he figured a .32 would save him from a bad bear, he said, "simple! I just shoot YOU in the knee..."
There's no free lunch, the .45 Colt
suitably loaded can stop anything walking in North American woods. The rest is up to the shooter. You can go more, there are bigger and more powerful rounds available today, but the same limit applies, success is up to the shooter WAY more than the cartridge.
Light, Powerful, cheap
pick any two
Light, Powerful, controllable
Pick any two
and so on...
Bears are not noted for their good eyesight, so if you don't hit them, at range (and in the right place) they aren't impressed with the caliber of your gun until they are close enough to read the markings on the barrel.
Bears do respect fire, but not firepower, until you hit them with it. Primitive man's best bear deterrent was probably a torch, and I do wonder why no one makes a small (gun sized) flamethrower for bear defense. Maybe the long term consequences of starting forest fires make the idea unpopular...
What is today called "situational awareness" is your best defensive weapon. Done right, it prevents needing to use the firearm. But, have a decent gun, anyway. Just in case. its always better to have it, and not need it than the reverse.