Really, any slug will do the trick if put on target. You can spend a fortune on Uber Super Slugs and such, and that is fine if you are hunting deer and want a 2" group at 100 yrds.....but for bear defense? You better be shooting inside 50, maybe 25 yrds at a charging bear or it isn't self defense anymore, is it? And at that range, any huge hunk of lead that you put on target will be equally effective. Just my .02, but the cheapo Federal blue box slugs, in 2 3/4" or 3" work just fine, and I can hammer stumps all day out to 75 yrds with them. Close enough for government work in my book. Also, as mentioned, 00 Buck up close works wonders on changing a bears direction. I generally alternate buck and slugs in my BPS when out and about. Luckily, it is all theoretical to me, never had to use it on anything. But ohhhhh, the tempation sometimes.