oralloy wrote:
My first choice in warding off a large bear would be a double rifle in 470 nitro express....
Good luck finding ammo for it. I personally believe that the mildest (smokeless) ammo you'll ever find for a 45/70 would flatten any bear. Nonetheless, for those who don't buy into that, there's always Garrett...
http://www.garrettcartridges.com/420.asp
That stuff will let an ordinary Marlin 45/70 kill anything which walks the Earth now and most likely, anything which ever did walk the Earth, now or in past ages.
Then again, if that's still not enough and you don't think you could handle the recoil of Hans Rudel's 37mm flack gun, there's always this:
http://www.thehighroad.org/showthread.php?t=123188
available, apparently, in 50 SW and also 50 Alaskan. The 50 Alaskan would be far the better choice, being another low-pressure rifle round like the 45/70. The problem in trying to get rifle-like power from pistol cartridges like the Cassul or the 50 SW is pressure, which you don't really want in a true lever-action gun like the Marlin. Browning's lever guns of course are basically just bolt action rifles with a lever to turn and operate the bolt.