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Samopal vzor 58 (Sa vz. 58) is czechoslovak automatic rifle intended for destroying manpower and light armored targets. It is gas-operated and can fire single shots or bursts. It uses 7.62 x 39 mm M43 rounds and the same 30-rounds magazine as AK-47. It is used by czech and slovak army.



Development
After end of World War II, &#268;eská zbrojovka and Zbrojovka Brno began designing weapon, based on german autoloading rifle StG 44 Sturmgewehr and it's ammunition 7,92x43 mm. But, because of ongoing development of new SMG (Sa vz. 23 and Sa vz.25), military administration didn't show any interest in this project.

After introducing 7,62x39 mm vz. 52 round, the military administration wanted to modify Sa vz. 23 and Sa vz. 25 to 7,62x39 mm vz. 52. This turned out to be non-attainable due to desing issues (unlocked breech, dynamic slide), so development of new weapon with locked breech has started. In 1953, tactical-technical requirements of "universal infantry rifle" was determined: effective range of 400 meters, good accuracy, maximal weight of 3.5 kg and using 7,62x39 mm vz. 52 round.

These projects were elaborated:
 * ZK 503 (designers Koucký bros. from Zbrojovka Brno)
 * &#268;Z 522 (designer Ji&#345;í &#268;ermák from &#268;eská zbrojovka)
 * ZB 530 (designer Václav Holek from Zbrojovka Brno)

When soviet round 7.62 x 39 mm M43 was introduced into czechoslovak army (and research was moved into Konstrukta Brno in 1954), new tactical-technical requirements was elaborated, and development was restarted under codename "Košt&#283;" (Broom). Ji& was set as leader developer. In 1958 this weapon was introduced into czechoslovak army under name 7,62mm samopal vzor 58.

Generally
Sa vz. 58 can fire single shot or bursts. It has 3-position mode-selector/safety on right side of frame above trigger. In "down" position the weapon is secured. In "front" position the weapon is firing bursts and in "back" position single shots. It is equipped with simple sights adjustable from 100 to 800 m (in 100m steps) and "universal" distance marked with "U". It is firing in front position of slide and it is using standard soviet 30-round magazine used in AK 47.

Main weapon parts

 * barrel
 * slide housing (with stock, understock, barrel guard and housing sleeve)
 * slide, composing of breech block with locking bolt, striker and extractor, breech block carrier with two springs and their guide rods, hammer (straight cock) and main spring with guide rod
 * trigger
 * sights (foresight and back sights)
 * fixed stock or folding shoulder stock

Design and operation
Sa vz. 58 uses powder gases, diverted from barrel by inclined gas pipe to gas cylinder, located above barrel. In cylinder, gases act on piston, whose piston-rod's back end leaning against breech block carrier, transferring gases' impulse on it. Piston with piston rod is returned into forward position by standalone piston spring. Linearly moving slide is locked by tilting bolt carried by breech block. Round initialization is mechanical, by ramming srtriker on round's primer. Hammer (speeded up by main spring) gives striker energy needed for primer initialization.

For burst fire trigger has so called automatical trigger, which releases striker just after slide has been locked. Whole slide is returned into front position by two springs, which are located above main spring. Shell case is extracted by extractor located on breech-block and ejected up and right by fixed ejector located in weapon's frame (behind magazine shaft).

Versions

 * 7,62 samopal vz. 58 P (p&#283;chotní - infantry) – with fixed stock
 * 7,62 samopal vz. 58 V (výsadkový - para/airborne) – with folding shoulder stock
 * 7,62 samopal vz. 58 Pi – with rail for attaching IR scope, flash suppressor and bipod

Sa vz. 58 and AK 47
At first appearance the Sa vz. 58 may look like just another clone of famous Kalashnikov AK 47. That's mistake. Of course, design is based on StG 44 Sturmgewehr and AK 47, but the most important part, the inner mechanism, is completely different and new. This specific breech-locking mechanism wasn't so used in other weapon so far.

Czechoslovak army made comparsion test between Sa vz. 58 and AK 47. Few rifles of each type was selected, dissassembled to pieces, and from those pieces were assembled 2 "new" rifles. From each rifle, total of 20000 rounds were shot. Nehind shooter stood few women which were loading magazines. When shooter depleted magazine, he reached back, got new one, loaded it and continued firing. After every 3 magazines, whole rifle was immersed into barrel with water to cool it down. After completing the test, both guns were dissassembled and damage to internal mechanism was evaluated. Both guns scored very well. In the whole test, one failure occured in both guns. In Sa vz. 58, lock return spring cracked (it has two).

Literature

 * &#268;eskoslovenské automatické zbran&#283; & jejich tv&#367;rci – Lubomír Popelínský (1999 Naše vojsko, Praha)