Whitworth, what do you consider using false information to discount a fine option?
The OP's 4" 500 weighs 56 oz, or 3.5 lbs. Your suggested revolver that he go out and spend ~$1,000 getting set up instead weighs 47 oz, or just under 3 lbs. That makes his revolver much more similar to your suggestion than what you assume it to be (4.5 lbs).
I wouldn't consider saving 9 oz to be a game changing difference compared to saving the money. Then there's the fact that the 9 oz heavier revolver opens the door to better performance.
But, if we go along with the "it's just a backup gun" and worthwhile to shop for a new revolver to save weight idea, we'd see lot's of steel 44 mag options in 37-40 oz range, and then the titanium and/or scandium 44's in the mid 20's oz range. Or, like others have noted, there's a good argument for his Glock 20.
It's all up to the OP to reason his best decision. Our best contribution is to give accurate facts for him to use.
You're right in that I am not a fan of the .500 Smith & Wesson Magnum. I have used them in the field on game and all that recoil, muzzle blast, heavy weight doesn't buy you anything over other .50 cals from a terminal standpoint, negating any "advantage" claimed or otherwise. I have trouble believing the accuracy of some of the weights posted on Smith & Wesson's website, given the overall girth of the .500. My 6 1/2-inch Model 29 weighs 51.2 ounces empty. I have real trouble believing the 4-inch X-frame is only 4 ounces heavier. Seriously. Considering the cylinder of the X-frame is 1.920-inches in diameter, length is 2.3-inches. The frame from the top strap to the midsection of the action bar ahead of the trigger guard is a whopping 2.85-inches, the same measurement the Ruger .454 SRH Toklat is 1.8-inch diameter, cylinder length is 1.750-inches and the same measurement of the frame is 2.650. The Toklat weighs 47 ounces -- 2.93 lbs versus the what 56 for an empty revolver? My .460 XVR weighed 76 ounces empty so I have some trouble believing the posted weights on Smith & Wesson's site. I assume since you are carrying it for bear defense you will probably load heavy hardcast loads and what will that add to it's rather impressive weight. All that girth makes for an unwieldy revolver and rather clumsy. I had a 6 1/2-inch that I let go of a few years ago and have never looked back.
Not to mention the horrendous muzzle blast of a 62,000 PSI round. I know, you will argue that you can load it down which then begs the question, why bother with a .500 Smith if not loading to potential. One could make a similar argument against the .454 Casull, I suppose. A 4-inch Redhawk in .45 Colt would be the cat's meow for the task at hand and they weigh only 46 ounces. There are some really good boutique loads in .45 Colt that I know work well on really big animals, like Garrett's 405 grain RHO (Redhawk Only) load.
Like .458 Lott said, the OP asked us our opinions on the .500 Smith collectively and many have taken a similar position to mine. If that is the only revolver the OP has access to, then by all means he should use it if he can shoot it well. I have had the benefit of using a whole slew of different revolvers and calibers on living and breathing targets, and have drawn my conclusions based on my experiences. Some, I suspect, have decided they like something and no amount of contrary information is going to sway them. So be it.
I'm not suggesting he goes out and buys anything, I'm only suggesting he consider other options as short X-frames are less than optimal in my experience. And having actually shed blood with the .500 Smith, that extra velocity potential isn't buying you much of anything terminally, but it does kick harder.
