I took my grizzly with my 338 Win Mag and a 210 gr Partition at 8 yards while on a mountain goat hunt. Came around a corner and he was at 20 yards. He ran to 40, and then turned and came back. Young bear, probably more curious than anything, but was too close for my comfort level! As his head was down, I shot him in the hump trying to break his spine, which it did. I waited a bit and threw a rock and whistled at him. His head came up, looked at me, then was trying to bite his shoulder, but could only move his head. When he stopped moving, I moved around and tried to put one in from the side. As he was in knee high grass I could not tell that he was laying in a small depression, and the bullet went into the dirt in front of his chest. He was still for a whle, so I went back around and whistled at him again. He raised his head slowly and glared at me and then lowered his head again. I cranked my scope up and could see his eyes through the grass looking at me. So I put one between the lookers. I didn't want to as I was hoping for the skull. Nothing left of it after that shot! Squared just over 6'.
Assisted my old mentor on his 2 grizzly LEH hunts. He was packing his 95 Big Bore in 356 Win loaded w/ 220 gr Speer Hot Cors. I backed him up with my BLR in 358 Win with same bullets. He took his grizzly on the first hunt @ 140 yards. Not the distance we were hoping for, but we ran out of cover. Unfortunately, we were downhill from the bear, something my Dad (who has guided for many grizzly (hates hunting them!), as did his father and grandfather - over 140 years of guiding in Alberta and BC between the 3 of them) and many of the old guides recommended against, but was our only option due to wind direction and location. His first shot was good and did knock the bear down. He got a little excited when the bear was immediately back up and swirling around biting at his wound in his side. It got a littler western from there! He dumped the rest of the shots into or at the bear as it was swirling around. 2 were misses, one in the front leg, and one in the neck that missed the spine. While he was reloading, I shot it once in the shoulder that knocked it down, and then he fired the finishing shot. The bear squared just over 7'. While the bear would have died from the first shot, it didn't occur as quick as one would like. Yes, it did kill, but an animals that can hurt you even when it is dead on its feet, requires additional shots until after it is dead. And even then an additional insurance shot is not an unwise thing. I continue to carry the BLR for back up on many hunts, but something with more power would be carried for back up on a grizzly hunt, such as my 376 Steyr. A full stocked, LH Ruger M77 with a 21" barrel, loaded with 260 gr AccuBonds.
I have also worked and played in grizzly country for many years and seen and been near these bears on many occasions, including guiding and performing bear watch for crews and groups. They make me nervous..not afraid to admit it...but I am less nervous when I can see and watch them, than I am when I know that they are close by in the brush and cannot see them and know what they are doing, And I have been tracked and followed by them on numerous occasions, where I could hear them, or have gone back later and found their tracks and where they have sat or laid to watch and listen. Mostly, I think that they are just plain curious...but I do not want to let my guard down and become a statistic either!
I has always read or heard in the old hunting movies that most guides wouldn't let you shoot a grizzly or a brown bear from beyond 100 yards. Doesn't seem to be the case today with modern cartridges, bullets and the long range hunting craze.
Yes smaller calibers can do the job. And shooting a cartridge/rifle combination that one is experienced, comfortable and confident in is very important. I would recommend the biggest that you are comfortable and practiced with.
And discuss tis with your outfitter.
I know the story mentioned about Donna Boddington, and it was the outfitter's requirement for a 375, not a regulatory requirement.
Even Craig's books and articles about north american game and cartridges discuss this topic in detail, and his recommendations are the same as I have mentioned above.
There are also a lot of guides that pack 338 Win Mags for back up on grizzly and brown bears. I also hear that the Ruger Guide Gun in 375 Ruger is a popular choice for a quick and handy bolt action rifle.
And yes, completely different from black bear hunting.
Most grizzly hunts are unsuccessful, Many of those that are, it is the first bear that presents an opportunity that are shot, resulting in the average bear being a 6' bear for an interior grizzly.
And brown bears are a lot bigger. Everyone tries for a 10' bear, btu I believe that there are a lot of 8' and 9' bears taken every year.
Interior grizzlies have a more notorious reputation for the behaviour and attitude compared to brown bears, but as with any animal, each has their own characteristics, personalities and attitudes!
Grizzly hunting has often been described as 95% boredom and 5% sheer terror.
Be prepared for a lot of glassing of a lot of territory to find a bear. Then be prepared for the stalk and shot opportunity when it comes.
Best of luck on your adventure when the time comes!
My grizzly bear was tasty! Fall bear eating berries. I wanted to get the rear quarters made into hams, but there was an issue with the meat cutter who said he could do this. I got my meat back, but never did get my hams.