Operating mechanism The vz. 58 is a
selective fire gas-operated weapon that bleeds expanding combustion gases generated in the
barrel from the ignited cartridge through a port drilled in the barrel, from the chamber, opening into a hollow cylinder located above the barrel that contains a short-stroke piston. The vz. 58 does not have a gas regulator and the full force of the gas pressure is exerted on the piston head, propelling it backwards in a single impulsive blow. The piston is driven back only when a shoulder on the piston rod butts against the seating and no further movement is possible. There is a light return spring held between the piston shoulder and the seating which returns the piston to its forward position. The gas cylinder is vented after the piston has traveled back and the remaining gases are exhausted into the atmosphere on the underside of the cylinder via two ports. The entire piston rod is
chromium-plated to reduce fouling. The locking system features a locking piece hinged from the bolt and housed in the bolt carrier that contains two locking lugs which descend into and engage locking shoulders in the
receiver's internal guide rails. The weapon is unlocked by the short tappet-like stroke of the piston rod as it strikes the bolt carrier and drives it rearwards. After of unrestricted travel, a wedge-like surface on the bolt carrier moves under the hinged breech locking piece and lifts it up and out of engagement with the locking recesses in the steel body. The hinged breech locking piece swings up and this movement provides the leverage required for
primary extraction. The breech block is then carried rearwards extracting the empty
cartridge casing from the chamber. A fixed ejector passes through a groove cut in the underside of the bolt and the case is flung upwards clear of the gun.
Features The spring-loaded
extractor and
firing pin are both housed inside the bolt, while the fixed ejector is slotted inside the receiver. The extractor retains the firing pin and is powered by its own plunger and spring. The weapon does not have a conventional rotating hammer but a linear hammer instead. The hammer is a steel cylinder hollowed from one end 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 so as to compensate for the very low ironsights on the vz. 58. Switching between the various options requires merely removal of a bolt at the rear of the receiver and swapping in the stock of choice.
Sights The rifle's
iron sights consist of a fully adjustable front post and a tangent rear sight with a sliding notch with range denominations from 100 to 800 m, graduated every 100 m. Besides this, the left side of the rear sight leaf is marked with the letter "U" (
univerzální meaning "universal"), for snap shooting, firing at moving targets and night combat at ranges up to 300 m. The rifle's sight radius is . The front sight base also serves as a mounting platform for the vz. 58 edged
bayonet.
Accessories Several modernization accessories have been manufactured for the vz. 58 platform from different companies. Accessories include "tactical" bolt release, extended and/or ambidextrous magazine release paddles, ambidextrous fire mode selectors, custom handguard rails, several types of sight mounting options and various muzzle brakes and compensators. Both civilian and military users use these upgrades, and they also see frequent use with
private military companies in the Middle East. Additional equipment supplied with the rifle includes: 4 spare magazines, a magazine pouch (in either canvas, leather, or leatherette), vz. 58 bayonet and scabbard, cleaning brush and rod, muzzle cap, oil bottle, unified sling, front sight adjustment tool, disassembly aid and a threaded
blank-firing adaptor. The vz. 58 also has a proprietary bipod, flash hider and scope mount for NSP-2 night vision scope (vz.58 P variant). Grenade launching inserts, as well as under barrel grenade launchers were developed but never adopted. ==Variants==