What type/brand of slug is best suited to anti-personnel usage? How about against bears? Also, considering one 00 buckshot pellet is on par with a .32 acp, does 00 buckshot provide effective incapacitation?
Every shotgun slug works "good enough" for "anti-personnel" - probably toss out the .410 - a full-caliber hole through something usually does the trick.
Those in the know regards bears recommend a shot through the nose if attacking. Same-same shot placement (= through the heart/lings, if not) .... just like a deer, whatever. Dave's comment is "there are no ineffective slugs." (I would add that you're using a 20-12 gauge slug & putting it in the right spot.)
I've played around with PMC's Brenneke slug lately in 12 gauge & am hugely impressed with accuracy (the slug will do the trick if placed right). A case of 20s on order & expect similar results. $2/box of 5 & couldn't be better tickled.
Not a lot of bears here in Md, except up in the mountains of western Md. Going on what I've heard from those in bear country, many park rangers who deal with problem bears use a pump or auto loader with slugs,00,or a mix of both. 12 gauges seem to be the rule here.
If I was in bear country and wanted a protective piece, I'd use an 870, with the first couple up slugs, backed up by a pair of full, not reduced power 00.
While fishing in the Northern parts of the continent, bears are not an uncommon sight.
A certain comfort is an 870 with an extended magazine loaded with Brenneke slugs. I've hunted enough deer to know that the slugs will break large bone structures and Brenneke's are tops for penetration. Buckshot won't get the job done unless you are nose to nose with the animal.
Bear attacks are very rare. I've seen them frequently in the north and they usually just go along their way. The best defense is proper food and garbage handling and woe betide the fisherman who guts his fish too close to camp. Most often noise will frighten the bears off. FWIW, I've seen my share of bears but never had a problem with any of them.