from the top of the magazine stack and chambering it. In single-action pistols this action keeps the hammer cocked back as the new round is chambered, keeping the gun ready to begin firing again. During World War One, detachable box magazines found favor, being used in all manner of firearms, such as pistols, light-machine guns, submachine guns, semi-automatic and automatic rifles. However, after the War to End All Wars, military planners failed to recognize the importance of automatic rifles and detachable box magazine concept, and instead maintained their traditional views and preference for clip-fed bolt-action rifles. As a result, many promising new automatic rifle designs that used detachable box magazines were abandoned. As World War II loomed, most of the world's major powers began to develop submachine guns fed by 20- to 40-round detachable box magazines. However, of the major powers, only the United States would adopt a general-issue semi-automatic rifle that used detachable box magazines: the M1 carbine with its 15-round magazines. As the war progressed the Germans developed the Sturmgewehr 44 assault rifle concept with its 30-round detachable magazine. After WWII, automatic weapons using detachable box magazines were developed and used by all of the world's armies. Today, detachable box magazines are the norm and they are so widely used that they are simply referred to as magazines or "mags" for short. Function and types All cartridge-based single-barrel firearms designed to fire more than a single shot without reloading require some form of magazine designed to store and feed cartridges to the firearm's action. Magazines come in many shapes and sizes, with the most common type in modern firearms being the detachable box type. Most magazines designed for use with a reciprocating bolt firearm (tube fed firearms being the exception) make use of a set of feed lips which stop the vertical motion of the cartridges out of the magazine but allow one cartridge at a time to be pushed forward (stripped) out of the feed lips by the firearm's bolt into the chamber. Some form of spring and follower combination is almost always used to feed cartridges to the lips which can be located either in the magazine (most removable box magazines) or built into the firearm (fixed box magazines). There are also two distinct styles to feed lips. In a single-feed design the top cartridge touches both lips and is commonly used in single-column box magazines,