Here it is. I think it's safe to say that there is no more powerful shoulder-fired weapon on earth. The two-bore cartridge fires a 3500 grain, or half-pound projectile! Buy one of these bad boys, and even if you miss the bear, you will rupture the tectonic plates of the earth between you and the bear, thereby preventing it's ability to reach you.
Here's a picture of the two-bore case. The "little" one on the left side is a .600 Nitro Express. The two-bore on the right side is more that 1.30" in diameter. More info here: http://www.2-bore.com/home.html