Personally not advocating shooting a bear, but would if it's all I had, and if properly loaded, would feel confident the killing power would be similar to a 30/30 at say under 100 yds. I'd be shocked if ballistic media test showed a top load in a 357 rifle, would be much worse than a 30/30.
Seems you have had experience with 357s on humans, but not bears. Picking cartridge choice for afield is often based on emotions, much as the buying and selling of stocks.
Agree on heavy hard cast (save a 140 Barnes) and brain shot and realize any marginal caliber requires exact shot placement to be most effective on stopping a large animal quickly. There are many better choices we all agree. I think a 44 with a heavy hard cast might surprise the hell out of someone who thinks the 30/30 will outpenetrate it. Higher vel with jacketed expanding bullet i.e. 30/30 often stops short of high momentum hard cast handgun bullets. Having shot both out of a TC handgun, I know which hit the ram much harder at 100 yds due to bullet blow up 30/30 vs. lack thereof, and sheer momentum due to bullet weight-44.
