Vt/u. 54c

The vt/u. 54 is a Kotaplan rifle chambered in the Marnin 6.91x47mm round. The rifle was designed and manufactured in Kotapla and accepted into service in 1959, as the vtor umopal 54 (submachine gun of 1954), replacing earlier Kotaplan rifles.

The Vt./u 54 bares a strong resemblance to Marnin assault rifles thanks to it using stocks, pistol grips, magazines and a modified Marnin handguard to make the rifle more compatible with the Marnin rifles in service with Kotapla.

History
Development of the weapon began in 1954; leading the project was chief engineer Felix Řehá assigned to the Konstrukta Mesko facility in the city of Mesko. The early vt./u 54's used furniture and magazines made in Kotapla, not to the Marnin standard, though the rifles used the Marnin round. Originally, the rifle was meant to use the 7.62x45 round used in the earlier vt/r. 50 self loading rifle.

Operating Mechanism
The vt. 54 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, 215 mm (8.5 in) from the chamber, opening into a hollow cylinder located above the barrel that contains a short-stroke piston. The vt. 54 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 19 mm (0.7 in) 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 16 mm (0.6 in) 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 prevent fouling.

The locking system features a locking block 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 22 mm (0.9 in) of unrestricted travel, a wedge-like surface on the bolt carrier moves under the breech locking piece and lifts it up and out of engagement with the locking recesses in the steel body. The 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.

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.

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", for snap shooting, firing at moving targets and night combat at ranges up to 300 m. The rifle's sight radius is 15 inches (38 cm). The front sight base also serves as a mounting platform for the bayonet.