As I explicitly stated "That study needs to be updated, since there are many more gun and bullet options now...." The methodology of the USFS study could probably also be updated, using more modern methods of testing.

However the point remains that if you choose to carry a firearm for bear protection, the best gun is the most powerful one that you can shoot well. The best test is performance on actual bears. The weapons I mentioned (375 H&H, 338 Win Mag, 12 gauge with slugs, etc) are some of those that have been very widely and very successfully used either in bear hunting or bear defense. Certainly many other calibers will also do the job.

I killed a brown bear on a hunt with one shot from a 338 Win Mag using 250 Nosler Partition bullets. I killed a black bear with my 30-06 with 220 gr bullets. Doing field work in the Brooks Range, my employer equipped us with 12 gauge pump shotguns using slugs. I spend a lot of time outside in Alaska. These days my personal choice is to carry bear spray. Spray has achieved very good results in actual bear charges, and is much lighter to carry than any firearm. Your choices may vary.