The Colt 1903 Pocket Hammer was a pistol produced by Colt for commercial sales, based on their earlier 1903 Sporting model, but at a more manageable length and with some refinements to the design. While it was their biggest commercial success in the .38 ACP caliber, kept in production into the late 1920s, it never achieved the success of the .45ACP M1911 or the .32ACP M1903 Pocket Hammerless.
The 1903 Pocket Hammer was designed by John Moses Browning as part of the "parallel ruler" series of pistols which eventually lead to the M1911. It was distinguished by its unsual construction, which had an open-faced slide with cone bushing barrel, attached to the frame by means of a transverse locking wedge similar to the Steyr 1912. While it was originally manufactured with a rounded hammer, later production incorporated a spurred hammer. While the pistol was originally a minor success, the introduction of the perfected .45 ACP M1911 made the 1903 Pocket Hammer obsolete. The pistol was catalogued until 1927 as the remaining guns and parts were sold off, and then quietly dropped.
The barrel is attached to the frame with two equal length links, one at the front and one at the rear. Upon firing, the slide and barrel move to the rear together, locked by interlocking lugs at the top of the chamber and the underside of the roof of the slide. As the rearward movement continues. the links rotate rearward and draw the barrel down, parallel to the frame. This downward motion pulls the barrel out of engagement with the slide, which is then free to move to the rear, completing the firing cycle. The slide is retained on the frame by a transversely mounted locking bar which is held in place by pressure from the recoil spring.
Cruffler.com Historic Firearm Of The Month June 2001