I've personally logged nearly 7500 miles of wilderness backpacking over the last 30 years.
In all that time I've only ever had one semi-dangerous encounter with a bear. As 'luck' would have it, that was the only time (since I was 18) that I had backpacked without a firearm. My friend and I hastily prepared to defend ourselves with a hand-axe and luckily the bear took off.
All things considered and presuming you follow proper food storage practices at night, your likely hood of being involved in a bear attack is INCREDIBLY remote. But that doesn't mean it won't happen...
I've never considered carrying any form of longgun...simply too much weight if you're travelling anything more then 10-15 miles. Especially if you're with a small group where you don't have as many bodies to distribute loads.
I've had maybe a dozen encounters with 2 legged critters where I thought things might go sideways. So all things considered I'm far more worried about 2 legged threats then 4 legged ones.
I've also seen dozens of mountain lions over the years and I've never had a problem with them either. I even had one lick me on the ear while I was sleeping
My normal backpacking piece is a .357 Mag S&W 340pd