I noted a lot of heavy caliber rifles, And I don’t disagree entirely, but my dad went hunting with three other friends in B.C. some years back, they encountered the very large black bear they had been stocking: With two .300 Win mags, one .338 win mag, and my dad with a .416 rem. mag. The charging bear took a total of 12 hits, the first 11 were totally ineffective, except for the 12th and final luckily shot, fired by a .300 win mag. that hit the jugular. killing the bear. Glen Douglas was the man with the bear tag, he won a trophy for his kill, it was the second largest black bear taken in B.C. up to that date. The largest was also taken that year, it was bigger than a small grizzly, or so I heard.the original story is just a repeat of one I heard, I don’t know its back ground, and heard it through a bear thread just like you, however the following story is a true account.
Basically big guns are a credit no doubt, but if you miss the sweet spot they dont seem to do quite so well as you might think, or so I've heard. (yeah, like I have a lot of expirence in this matter

My primary objective would be a mass of fire, with a round strong enough to penetrate a bears spine, the spine is the thickest and hardest bone matter in all our body’s, if it takes a hit it often shatters even large cal. bullets, and a grizzly’s skull is so thick it can deflect most rifle rounds up to .416 or .458 rem. mag. (this is most often due to angle of impact not the shear thickness.)But in the case of the spine, they often still penitrate and break the spine, and hit so hard it does shock damage, when put together, this damage can kill the animal instantly. But you have to hit the right spot, preferably upper spine, (the closer to the skull the better) or else it may not matter what caliber your useing, short of a .50BMG. Which hits with no less than 25,000 foot lbs of energy. 4.5x what a .458 rem.mag. hits with. However most all Fifty's weigh in at 25-30 lbs unloaded. Are you really going to carry that around with you?? thats like packing a large TV set made in the early 60's!
