Tactical Wire just wrote a a review of the Smith and Wesson revolver as a good choice for a backup carry gun.

A backup gun to complement the excellent M&P auto pistols and M&P15 carbines, the M&P340 is a Scandium frame super-light Magnum revolver. I’d avoided flyweight Magnums before this one. The steel small-frame guns got to be too much for me to shoot with any regularity.