My experience with black bears (5x) is that you hit 'em in the "boiler room" and they are down and dead in seconds. Less than 10. The only way to top that is a head shot I suppose. And mine were with archery equipment.
It sounds like for the most part the hounds tree the bear in which case your 30-30 in the right spot has plenty of power and close range to do the job quickly.
As discussed, you have lots of ways to go regarding a "trapper" sort of thing if you feel a change is in order.
The only other thing I'll toss out is a cut 12 gauge w/slug. Possibly the stock as well. That would be short, light weight and powerful. Having said that, I'd stick with the 30-30 unless an upgrade falls into your lap.
Southern,
Those few seconds can do some real damage to a fine hound dog. We've had several dogs to get injured this year due to poor or misplaced shots that were ultimately lethal just not immediately so. Most the bear I have taken were indeed treed but it seems our local bears are more prone to baying or even crawling in a "hole" under a rock ( makes for a REALLY interesting harvest sequence) lately. Last year I was within 10 yards of fairly large bears on two occasions and couldn't get off a shot due to either dogs being in the way or insufficient time when shot opportunities presented themselves.
You are certainly correct that my existing 30-30 is ample medicine but why have one gun when I can have two for the same purpose. Still, there are other projects pending so something will need to fall into my lap or come with an attractive price tag.
Finally, some guys do carry shotguns. My first bear was taken with a NEF single shot 12 ga although most who carry a scattergun trend to a pump or auto. There are times, however rare, where a shot opportunity is up to 100 yrds to I'd like to stick with a rifle. Now that I type this out I realize how specialized the criteria are for these hunts!
