RE: grizzly caliber
IMHO a grizzly cartridge starts with the .338 Winchester magnum and goes up from there.
.338 Win mag, .338 ultra mag, .330 Dakota, 35 Whelen, 350 Rem mag, .358 norma mag,.375 H&H, 375 ultra mag and the Weatherbys of the same bore diameter. Then of course the big bore levers like the 45-70, 444 Marlin, and 450 Marlin.
IMHO dangerous game is not the place to rely on shot placement. I like to use a .270 elk hunting but I have the luxury of waiting for the right shot. Something I might not be able to do if I startle a Grizzly or make a bad shot and really piss one off.