They don't call the Remington 7400 "jam-amatic" for nothing.

Are you not listening to any of the advice we are giving you?

If you are buying a gun specifically for the purpose of being able to stop a Grizzly bear attack then forget about any gun chambered in a cartridge with a bullet smaller than .338 inches. This would start at the 338 Winchester magnum and go up from there.

Forget about a semi auto rifle. You can bet that if you need it to save your life it will jam up. You may have fired 10,000 rounds before hand but that one jam will be when the rare bear decides you are food. And besides that most do not fire a cartridge larger than a 300 magnum. While it is definetly a bear killing cartridge it is not a bear stopping cartridge.

You want a firearm that will throw large and heavy chunks of lead at the bear. This would include cartridges such as the 444 Marlin, 45-70, 450 Marlin, 375 H&H, 375 JDJ, 458 Winchester, and the 12 Gga shotgun firing slugs or large buckshot.