Smith & Wesson Model 646

The Smith & Wesson Model 646 is a six-shot, double-action revolver chambered for the .40 S&W pistol cartridge, manufactured by the U.S. company Smith & Wesson.

It was only produced for one year, and did not catch on quite as well as Smith & Wesson had hoped.

Design
The 646 was offered in a stainless steel finish with titanium cylinder. Production was limited to 300 guns. It was offered in a standard L frame and a Performance Center version; a space-age looking stainless steel revolver with a slab-sided heavy barrel and matte gray titanium cylinder.

Operation and availability
The 646 is unusual in that it is a revolver chambered for a rimless cartridge generally used only for semi-automatic pistols. In order to effectively use the rimless .40 S&W cartridge, the revolver utilized moon clips, a metal flange which holds the cartridges in place for loading and ejection. But unlike other moon clip revolvers such as the 610 and 625, the 646 generally wouldn't fire a cartridge without the clips. Dogged by persistent complaints of sticky extraction, ignition problems caused by varying rim thickness on factory .40 ammo, and a MSRP just shy of $850, it vanished without much comment after its short run.