At last and finally I have found the answer to this internet wide question, 'what is the best gun for bear defense'. It is this;
The Colt Bulldog Gatlin gun. Chambered in 45-70 and capable of delivering 1000rds/minute, if you can fill it quick enough. You just need a strong back to haul it and I am not sure if Diamond leather make a holster for it yet.
'But it's an automatic weapon and just in museums'. Not so on either count, as it is hand-cranked it falls into one of those strange BATF loopholes that means any of us who can legally buy guns could own one (I understand, but may be wrong).
And Colt is making a limited run of 50, 2 per month over the next 2 years. If you have $43,000 (yep that's three zeros) and a strong back, this is the bear gun for you.
Would look pretty cool mounted on the front of an ATV or snow-machine!!