almost throughout its entire length to accommodate its own operating spring. At the open end of the cylinder, a plate is welded and a groove is cut in each side of this to slide on the receiver guide rails. This linear hammer enters the hollow bolt and drives a free-floating firing pin forward with each shot. The vz.58 uses a trigger mechanism with a lever-type fire mode selector, which is also a manual safety against accidental discharge. When the selector lever is placed in its rear position ("1"—single fire) the sear is disabled and the left hammer catch is rotated by the disconnector, which is depressed by the bolt carrier after every shot and is therefore disconnected from the hammer catch. The forward setting of the selector lever ("30"—automatic fire) disables the disconnector, and the left hammer catch meshes with the sear mechanism. The center ("safe") setting with the selector lever pointing vertically downwards, mechanically lowers the trigger bar and the disconnector so there is no connection between the trigger and the semi-automatic sear which holds the hammer. The rifle also has an internal safety, which prevents the weapon from discharging when out of battery. The right linear hammer catch disables it, and it can only be released by pulling the charging handle back and cocking the weapon. The weapon is fed from a detachable box magazine with a 30-round cartridge capacity and made from a lightweight aluminium alloy. When the last round from the magazine is fired, the bolt will remain locked open on the bolt catch, activated by the magazine's follower. The magazine release tab is located at the base of the receiver on the left side, behind the magazine well. The bolt carrier has a built-in guide rail used for reloading from 10-round stripper clips (from the SKS rifle). Despite their similarity, vz. 58 magazines are not interchangeable with those of the Kalashnikov-pattern weapons. An interesting feature on this rifle is the ability to quickly change the type of stock. The vz. 58 can appear either with its original fixed stock (in either beech wood or composite material) or folding steel stock, or with one of the many aftermarket stocks available – including AR-15 style stock adapters that mount a buffer tube to the receiver. The latter usually has the buffer tube slightly angled down as to compensate for the very low ironsights on the vz. 58.