Can 5.56 rounds stop a bear attack?
The Germans use 5.6x57mm RWS with bullets 60gr or so for red deer. You can get similar bullets at similar velocity for 5.56x45mm ARs which are adequate for whitetail deer (used only where the caliber/energy levels are legal under state game laws.)
Personally, I don't think 5.56 is adequate for stopping a bear attack. I don't bear hunt but black bear attack is a possibility (defending against a bear attack would initially be treated as an illegal bear kill so I consciously practice bear avoidance when in the mountains; they are cool to observe from a distance). The lightest gun I own that I would consider adequate for bear protection is my 6.5mm Carcano with 160gr bullet ~2000 fps for deep penetration. Marlin in .30-30 Winchester second step up. Then my .303 Enfield. What I have heard is recommended for bear defense in Alaska as a minimum is the 12ga with 1 ounce slug. The last time we camped out on the mountain on family property in Tennessee we had 12ga just in case.
I notice the opening post is from a member in Seattle WA. Washington State has bigger bears. I have been warned by people with more experience than myself that 5.56 does not have the penetration or bullet momentum to reliably kill eastern black bear. I will opine that 5.56 does not have the penetration or bullet weight to stop a western brown or grizzly bear in attack mode.
I don't know bear anatomy well enough to determine what would be "perfect placement" with an inadequate round; in a bear attack I would prefer to bet my life on center-of-mass with 12ga 1 ounce slug. Poaching does involve taking the time to place a shot perfectly; as I recall, the reason we saw no deer on the mountain in the 1950s was that folks had fed their families during the Depression by shooting deer with squirrel rifles until there was no sustainable deer population left (but they have made a comeback). Defense against bear attack does not allow time for surgical shot placement.
As far as scaring a bear away, people have stood their ground like they belonged where they were and yelled at bears to go away; bears supposedly respect other critter's territory as long as their own is not threatened (or at least it worked for Anthony Hopkins in
The Edge).
I don't know about Washington State but in Tennessee I expect a self-defense shooting of a bear to be treated as an illegal kill until some kind of hearing: initial forfeit of gun and vehicle and fine, unless the hearing determines self-defense and not poaching.
I do wish the opening post had been
Can X caliber stop a charging bear? Then I could have recycled my old answer to
that question: only if you're good enough to shoot the card out of its paw. (Come to think of it, I stole that joke from someone else. Shameless.)
I'm confident a 30 rounder FMJ blast coming from a full auto M16 may stop a grizzly attack
I'm confident in a grizzly attack that a 30 rounder FMJ blast coming from a full auto M16 may have the first two or three rounds on the target and the rest on the countryside.
