The S&W 686 is a L-frame. The original 357Mag revolver was a large N-frame M27. Since it was used often as a duty gun, police officers began complaining about the size and weight of the revolver. The result was the K-frame M 19. The K-frame is typically a 38spl frame. After years of shooting and training, standard power 357Mag loads were starting to trash the smaller K-frame guns and the L-frame 586 and 686 models were born. The L-frame is basically a beefed up K-frame revolver designed to handle full power 357Mag loads. In my opinion the L-frame is the perfect size and weight revolver for the 357Mag. There are also J-frames which are typically the tiny 5-shot 38spl and 357Mag revolvers with 2-3" barrels.
