They often didn't survive.
Hence why now a days they use modern firearms.
As much as I love my 30/30 I'd feel better having my 45/70 with me in big bear country. Also nothing wrong with a good 12 gauge but personally I find the ammo too bulky...it's preference thing.
I would think more died from starvation then Grizzly attacks.
No doubt bigger is better (if you can shoot it well) against a big bear but keeping a cool head is the main thing that's going to allow you to not have to shoot in most cases.