Welcome to the site!
Interesting situation you have set-up. I'd agree with Bisley's analysis, above, but I also think that goNYG's comment is pertinent; what kind of person are you talking about? Although the larger caliber magnum revolvers are very potent, they are so large and cumbersome that most folks would not be wearing/carrying one without darn good reason -- and concealment would be difficult, if not impossible, depending on the circumstances. For a true "just-in-case" handgun, but still being more powerful than normal and a little bit unique, a short-barreled .44 Magnum revolver or a Glock 20 or 20C would be much more believable, IMO.
"Placement is power" -- seen in an article by Stephen A. Camp
(RIP, Mr. Camp; you will be remembered, and missed)