Ok, what a fun read this was!!!!
Now i got a few thing's to add, Chuck Adams completed the grand slam using a bow & arrow to harvest one each of all North American large game animals. I'm an avid bow hunter myself, and would certainly feel alot more comfortable with my .375 win than with a bow. I hope you can see what i'm getting at here, in a pinch i'd like to complete a grand slam someday using my favorite rifle the .375 win cal. I have no doubt's about it being able to knock down a grizzly bear, but i thank you all for your opinion's.
Now lets look at one last thing, fact the 45-70 has a proven track record and alot more power. However, it also has alot more recoil, and i shoot a .375 much better. I like the light weight and ease of handling without the recoil of a .45 cal. Just for instance i shoot this gun better, and could likely place multiple shot's into Grizzly bear more accurately and faster than i could with a 45-70! My opinion is it's alot easier to handle, point, and carry than a 45-70. Plus like i said, i would get alot more satisfaction out of killing a grizzly with my .375 like Chuck Adams probably does using a bow.
I know its an odd choice but that's exactly why i like it, and want to use it. Just about anybody can go get a 45-70 and kill a grizzly, what funs that? ;-) I think a good hard cast bullet would be the way to go but the Barnes 255 gr flat nose is certainly a stout a bullet. Again thanks for your input, i have really enjoyed reading this post. If i ever do get the chance to hunt a Grizzly their's no other gun i would take....