When I went to hunt Cape Buffalo on purpose, I used a 450 Dakota.
Can you kill one with a 338? Sure. Is it "great" for Cape Buffalo? I don't think so.
Same deal for the 30-30 and Bear.
I bought hundreds of 150gr TSXFN for 30 cents each and if I ever hunted deer or elk in grizzly country with a 30-30, I'd be sure using the X bullet. Actually, I'd probably use my 300 or 375 H&H.