There was a grizzly killed in AK in the early 20th century. Two guys were in a drainage looking for gold. A few years previous a man had gone into the area with a 33 WCF and a 38 Long Colt revolver but did not come back.
The two noted that there was something in the area that made a lot of groaning noises and seemed to not like them much.
It was a fairly large Gbear. If was stalking them and finally charges one prospector and his dog. The dog distracted the bear and as it ran past the guy at close range he gave it a 38-72 WCF slug in the shoulder. This or a followup shot (would have to get the book out and read it)did for the bear.
A postmortem on "Old Groaner" reveled he had a broken jaw that never healed and had a healed over eye socket. There was a 33 WCF in the bad eye socket, another had broken the jaw. There were several 38 cal pistol bullets in the underside of the bears neck and chest.
It was a bad day it would seem for the owner of the 33 WCF (200 gr bullet at about 2200 fps). Its actually a pretty good elk gun. Friend has one he inherited.
So as with all such things there are always variables. If you shoot the bear in the head and break its jaw it can still kill you. The 38 long Colt was well proven to not be able to even stop a man with solid chest shots. So shooting a bear with it is an exercise in futility.
So I have a friend who killed a Gbear with a 22. A documented report of a guy shooting one about 2004 with a 9mm pistol with the desired results. Anecdotal reports of a head shot with a modern 45-70 load. I read a report of a guy killing a charging bear with a 30-30. IIRC he missed the world record skull because the bullet knocked off a piece of skull as is exited the back of the head shortening it.
Then we have "Old Groaner".
Now the 33 WCF is no popgun. Its like a super 30-30. Why did it stop in the eye socket? Maybe it hit a tree limb first, maybe he had bad ammo.
There is a documented report of a prison warden in MT shooting a knife wielding convict during a prison riot with no effect. The guy was in the act of stabbing a man in the wardens OFFICE when he shot him in the head at a range of INCHES with a 41 Long Colt Revolver with NO EFFECT or significant penetration. Head shots on people USUALLY work and subsequent testing by the Warden resulted in a nasty letter to the ammo maker (Win. IIRC) since it would not penetrate a pine board.
So there are a host of possible out comes.
Shooting an angery bear at close range is a have to. Not a want to. How it turns out will be determined by many factors. There is luck, bullet design, weight and velocity and the determination of the bear and the shooter.
Yes, almost anything will stop bear if it hits the right spot and will penetrate adequately. Even some very powerful modern rifles sometimes fail in this however.
There was an excellent video of a bear hunt where the guided hunter shot a large boar twice IIRC and they were then charged by a sow from 100-150 yards away who they could not even see. The sow came on even though 3-4 people were shouting and waving their arms. The guide shot her in self-defense at about 8-10 feet. The bear then turned and moves off, hurt but at good speed about 80-100 yards and collapsed.
F&G cleared the guide, it was well documented by video but the guide was put out since shooting a sow reduced the bear population unnecessarily and thus reduced his income potential. Plus the extra work and explanations to F&G.
The vast majority of our posts here are from anecdotal or written accounts. Few of us are going to see much less shoot a big bear or be forced to shoot a bear with a flintlock. If you think its a possibility or you intend to hunt large bears with one use a large round ball, one ounce or heavier, a heavy charge or powder, 1500-1600 fps and place the shot where it will disable the bear the first shot. This means looking at the bears anatomy or relying on a guide to instruct you. I would choose a shot that would break shoulders and perhaps shock the spine. IF THIS WAS POSSIBLE.
If the range as close and all I had was a head shot its going the be that.
I am paraphrasing here, Forsythe IIRC, who said that a hunter should never pull the trigger on an animal unless he was sure he could kill or crippled with the first shot. Be it the timid kind they fly FROM you or the kind that fly AT you.
Animals, deer, Elk, Moose, Bear, Tiger, etc can sometimes be extremely bullet resistant. But the Elk is not likely to attack and shred the hunter if poorly hit. Predators, even relatively small ones sometimes do.
Yes a FL will stop/kill/disable a bear, or a leopard or a Tiger. All have been killed with FLs at some time or another. How the powder is ignited has nothing to do with the projectiles effectiveness.
Dan