I had the opportunity to hunt in British Columbia in 1987 for grizzly. I was going to use my 7MM. Rem. Mag. for the hunt. The outfitter described the 7mm as marginal for this bear. His recommendation was the 375 H&H. That is what I used and might I add, very glad with the decision when I saw the bear that I eventually shot. I would think that the 30:06 would do the job IF the bear is not in an aggressive stance. When a grizzly adrenalines, you what more than the 30:06. I'm sure many big bear have been harvested with this great caliber, but I wouldn't go looking for this kind of trouble with this caliber.