and requires a device known as a magazine release to allow the magazine to be separated from the firearm. The Lee–Metford rifle, developed in 1888, was one of the first rifles to use a detachable box magazine, and the spare one could be optionally worn on soldier equipment, although with the adoption of the Short Magazine Lee–Enfield Mk I this became only detachable for cleaning and not swapped to reload the weapon. However, the first completely modern removable box magazine was patented in 1908 by Arthur Savage for the Savage Model 99 (1899), although it was not implemented on the 99 until 1965. Other guns did not adopt all of its features until his patent expired in 1942: It has shoulders to retain cartridges when it is removed from the rifle. It operates reliably with cartridges of different lengths. It is insertable and removable at any time with any number of cartridges. These features allow the operator to reload the gun infrequently, carry magazines rather than loose cartridges, and to easily change the types of cartridges in the field. The magazine is assembled from inexpensive stamped sheet metal. It also includes a crucial safety feature for hunting dangerous game: when empty the follower stops the bolt from engaging the chamber, informing the operator that the gun is empty before any attempt to fire. The first successful semi-automatic pistol was the Borchardt C-93 (1893) and incorporated detachable box magazines. Nearly all subsequent semiautomatic pistol designs adopted detachable box magazines. The Swiss Army evaluated the Luger pistol using a detachable box magazine in 7.65×21mm Parabellum and adopted it in 1900 as its standard sidearm. The Luger pistol was accepted by the Imperial German Navy in 1904. This version is known as Pistole 04 (or P.04). In 1908 the German Army adopted the Luger to replace the Reichsrevolver in front-line service. The Pistole 08 (or P.08) was chambered in 9×19mm Parabellum. The P.08 was the usual side arm for German Army personnel in both World Wars. The M1911 semi-automatic pistol set the standard for most modern handguns and likewise the mechanics of the handgun magazine. In most handguns the magazine follower engages a slide-stop to hold the slide back and keep the firearm out of battery when the magazine is empty and all rounds fired. Upon inserting a loaded magazine, the user depresses the slide stop, throwing the slide forward, stripping a round