Something persuasive...with larger bears, something like a Ruger Blackhawk in .41 Magnum or a Redhawk in .44 Magnum. For mountain lion, a .357 Magnum would make sense to me.

Bad advice. It's just extra weight. Your friend has a much better chance of getting struck by lighting or tree falling on him than needing a "backup gun" for bears or mountain lion. Is he going to wear a lightning rod on his head? I hunted elk hard for more than twenty years and even had my own pack string. Could always tell the greenhorns. They had a useless hog leg strapped to their thigh. I kept a .357 Highway Patrolman in the saddlebag. If I had a problem on the trail it was easier to get it out of the bag than pull rifle out of scabbard. Also, I never wanted to take a rifle on fishing trips. For fishing a handgun is definitely the way to go (not a "backup" weapon though). But big game hunting, no! Your friend will just advertise his dude-iness.

I take a Glock 20 10mm. It holds 15 plus 1 rounds and hits like a sledgehammer.

I won't pretend to know it all about this topic, but I can tell you that ANY deer or elk rifle is a better self defense tool than any handgun caliber. What? You are going to lay down your rifle to draw a pistol? I seldom carry both although I do take a .357 or .41 magnum revolver along when checking cameras, placing or retrieving stands, etc. when carrying a rifle is not practical or allowed (regs). Also, I don't carry a big rifle to kill deer or even elk, it's those other critters that I match my rifle to. Accordingly, anytime I hunt whee there are bears of any flavor or big cats, a .30-06 is bare minimum for me.

Hmmm, the original post did not state bowhunting but if I were bow hunting in big cat or bear country, I would consider one of the above firearms as a backup.

I agree with 99. +1

I cannot imagine hunting elk with some big pistol strapped to my side. For you guys who sit in a tree stand or ground blind, you really have no concept what it's like to go after elk. I mean really go after them. You're on your feet all day, day after day, going up and down mountains, through brushy gullies, across streams, wading snow drifts, etc., etc. Besides being a lot of extra weight that you'll be cursing before the day is half done, a sidearm will pull your pants down and gets caught on brush, etc. Just a damned nuisance. I always had a pistol with me when I was elk hunting - K22 revolver stuffed in the daypack and loaded with .22 longs for blue grouse. Not a showpiece and entirely functional. It more often than not brought home five times its weight in meat (often times to my regret by the end of the day!)

And for those who are going elk hunting with a bow, the bears and big cats will be the least of your worries. Elk are pretty savvy about tree stands and I don't know of anyone who's had much success hunting them that way. Most try bugling bulls and do it from the ground. But be ready to shoot or die! Unlike a bull moose, bull elk completely lose all sense of reality when they get worked up. When they are on the prod they are literally blinded by passion. You will not have time to reach for a sidearm if a bull is coming full tilt. Bow hunting for bull elk is perhaps every bit as dangerous as for bears. It's not for the faint of heart or the inexperienced.

Good advice. I had that stuff strapped to my belt every day in Alaska and was absolutely confident in its ability. Not so much my marksmanship with a pistol at a charging animal. I'm sure it will work just as well if not better on big cats. But it doesn't look very macho!

.44 rem mag or a .500 S&W.

The speed and tenacity of a big bear is not to be doubted. I have no desire to aggravate one with a pistol. There is just not enough stopping power. I haven't shot a bear with one but I have shot a charging Russian boar with a hot .44 Mag and was shocked at its lack of shocking power and stopping power. I don't hunt hogs on the ground with only a .44 anymore. I can only imagine what kind of trouble I could expect with a big bear.

In addition, I am among those who would rather not carry an additional four pounds for nothing. If I am rifle hunting, I will depend on my rifle all the way. I would carry a .22 pistol though to finish off any game that is still alive upon my arrival.

I remember those days well, 4 years in Alaska running the largest and busiest range in Central AK and those guys with their 454 Casuals etc blasting away on the range. I would ask if they were using them for bear protection and every one of them would say yes. "Did you know it’s State and Federal law that you must remove the front sight off your hand cannon". They knew they they were in serious trouble while looking at the massive front sight that would pass for an Farm Implement. Why they asked? You going to shoot a bear with that right? Ya they said. Well that bear is going to slap that hand cannon out of your hand and shove it up your, and I would leave it right there and walk off. Yep! Had a lot of fun I did! But my case and point is this, nothing smaller than a 44 Mag and don’t rely on it as you first line of defense. A good reliable rifle such as 308/30-06 or larger that you can manage instantly, accurately with quick follow up shots is your best choice.

This has been a "NO LIE GI" moment!

You mean about the testosterone-laden pachyderm?

Jay, have you ever noticed the wind conditions in bear country? Need to think that one throng! I always wondered where those chili peppers in bear scat cam from?

Clay,
Had a hunch my story would bring out your front sight comment. Where have you been?

When bowhunting for whitetails (from a treestand), I usually have a Super Blackhawk handy, loaded with Speer 300 gr. soft points. I'm not afraid, but I ain't stupid either, I have no plans to beat a bear or pack of coyotes off my feet with an arrow.

No prairie in the Flathead. You need a lesson in geography, Mr. Wannabee.

Of course if you are hunting with your neighbor a .22 is all you need. Just shoot him in the knee cap and while the bear is busy with him walk away briskly. You also get another parking space out of the deal.

the only time I have had any hint of anything after me was when I walked back out of a hunting area and found mountain lion tracks in my tracks. had no idea he was there, I was carrying a side arm but it would not have mattered if it was a 9mm or a 454 that thing could have been on me and I would have been screwed before I ever even had a chance to think about using any firearm