For self defense against griz, the .44 mag is more than capable of drilling into the bear's brain and other vitals.
This is some crazy talk. It falls right into the same camp as those folks who say "a .22 LR will kill a deer plenty dead!" Yes, the round can do that job. Barely. Under perfect conditions. Sometimes. No one who knows what they're talking about goes into grizzly country and says, "my .44 Mag will protect me from an enraged Grizz -- no worries." When a 12 ga. with slugs is seen as just ok for the job, a .44 Mag is, literally, "better than nothing."
Do you think a S&W 500 is going to lift the bear into the air and throw it back against a tree? It just isn't going to happen, and the bullet size and weight difference isn't going to make that much of an advantage.
Again, craziness! More weight, faster, does more damage, penetrates farther, fights through more tissue and bone, gives you just that much more advantage. Of course it won't toss the bear aside like a rag doll. Firearms cartridges all lie somewhere on a power spectrum. The farther up that spectrum you can go -- and still control the gun and make effective hits -- the better off you are. This is not debatable.
Shoot an enraged griz in a non-vital area with either caliber and you're going to be hurting. Hit it in a vital area with either and it's the bear that will be hurting. All in all, I'd rather have a second shot option than to put my money into a one-shot cannon that is 8-10 ounces heavier. (Getting a second shot with the 29 will be problematic, but not impossible.)
You don't shoot large revolvers much, do you? Getting off a second shot with a heavy .44 Mag is not any kind of a big deal for a practiced large-bore shooter. I can draw and empty the cylinder of my 4" 629 -- into the scoring zone of a silhouette target, in about 2.5 sec. with .44 Spec. loads. With 300 gr. loads at 1,200 fps (the hottest rounds I put through mine) my time for that drill jumps up by about 1-1.5 sec. So 6 heavy rounds in 3-3.5 sec. Gonna be slower with a .500 Mag, sure. But to say it will be a "single shot" 'cause you just can't get off one more? Get outta here! That's silly. If you're facing down a mad grizzly or brown bear you'll have fired all 5 before you even realize it.
If the extra weight and velocity of the S&W 500's rounds would be welcome if they could be delivered without the extra weight of the gun or the additional recoil. But these prices are too high for what the gun actually delivers.
Yeah? For you. You've explored the platform and it isn't for you. Ok. But there are a lot of folks who feel the same way about .357s in a 642. Heck, there's folks who don't like the "heavy recoil" of a .45ACP. Everybody's got to know their limitations -- but don't preach that YOURS are universal and must apply to others.
Especially when lots of folks have explained that they shoot their .500s FOR FUN with heavy loads. If someone puts 700 gr. slugs through their .500 regularly, just because they enjoy it, chances are they'll do o.k. with the gun for defensive purposes.
-Sam