shots. The disadvantage of this is that the long, heavy pull cocking the hammer makes the double-action revolver much harder to shoot accurately than a single-action revolver (although cocking the hammer of a double-action reduces the length and weight of the trigger pull). A rare class of revolvers, called automatic for its firing design, attempts to overcome this restriction, giving the high speed of a double-action with the trigger effort of a single-action. The Webley-Fosbery Automatic Revolver is the most famous commercial example. It was recoil-operated, and the cylinder and barrel recoiled backwards to cock the hammer and revolve the cylinder. Cam grooves were milled on the outside of the cylinder to provide a means of advancing to the next chamber—half a turn as the cylinder moved back, and half a turn as it moved forward. .38 caliber versions held eight shots, .455 caliber versions six. At the time, the few available automatic pistols were larger, less reliable, and more expensive. The automatic revolver was popular when it first came out, but was quickly superseded by the creation of reliable, inexpensive semi-automatic pistols. In 1997, the Mateba company developed a type of recoil-operated automatic revolver, commercially named the Mateba Autorevolver, which uses the recoil energy to auto-rotate a normal revolver cylinder holding six or seven cartridges, depending on the model. The company has made several versions of its Autorevolver, including longer-barrelled and carbine variations, chambered in .357 Magnum, .44 Magnum and .454 Casull. The Pancor Jackhammer is a combat shotgun based on a similar mechanism to an automatic revolver. It uses a blow-forward action to move the barrel forward (which unlocks it from the cylinder) and then rotate the cylinder and cock the hammer. Revolving long guns Revolvers were not limited to handguns and as a longer barrelled arm is more useful in military applications than a sidearm, the idea was applied to both rifles and shotguns throughout the history of the revolver mechanism with mixed degrees of success. Rifles Revolving rifles were an attempt to increase the rate of fire of rifles by combining them with the revolving firing mechanism that had been developed earlier for revolving pistols. Colt began experimenting with revolving rifles in the early 19th century, making them in a variety of calibers and barrel lengths. Colt revolving rifles were the first repeating rifles adopted by the U.S. Government, but they had their problems. They were