The Smith & Wesson Model 646 is a six-shot, double-action revolver

Revolver

A revolver is a repeating firearm that has a cylinder containing multiple chambers and at least one barrel for firing. The first revolver ever made was built by Elisha Collier in 1818. The percussion cap revolver was invented by Samuel Colt in 1836. This weapon became known as the Colt Paterson...

 chambered for the .40 S&W

.40 S&W

The .40 S&W is a rimless pistol cartridge developed jointly by major American firearms manufacturers Winchester and Smith & Wesson. The .40 S&W was developed from the ground up as a law enforcement cartridge designed to duplicate performance of the FBI's reduced velocity 10mm cartridge which could...

 cartridge

Cartridge (firearms)

A cartridge, also called a round, packages the bullet, gunpowder and primer into a single metallic case precisely made to fit the firing chamber of a firearm. The primer is a small charge of impact-sensitive chemical that may be located at the center of the case head or at its rim . Electrically...

, manufactured by the U.S.

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 company Smith & Wesson

Smith & Wesson

Smith & Wesson is the largest manufacturer of handguns in the United States. The corporate headquarters is in Springfield, Massachusetts. Founded in 1852, Smith & Wesson's pistols and revolvers have become standard issue to police and armed forces throughout the world...

. The 646 is unusual in that is was 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.

The 646 was offered in a stainless steel finish.