The Škorpion vz. 61 is a Czechoslovak 7.65 mm machine pistol developed in 1959 by Miroslav Rybář (1924–1970) and produced under the official designation Samopal vzor 61(“submachine gun model 1961”) by the Česká zbrojovka arms factory in Uherský Brod from 1961 to 1979.
Although it was developed for use with security forces and special forces, the weapon was also accepted into service with the Czechoslovak Army, as a personal sidearm for lower-ranking army staff, vehicle drivers, armoured vehicle personnel and special forces. Currently the weapon is in use with the armed forces of several countries as a sidearm. The Škorpion was also licence-built in Yugoslavia, designated M84. It features a synthetic pistol grip compared to the original version. A civilian, semi-automatic version was also produced, known as the M84A, also available in .380 ACP (9×17mm Short).
The Škorpion is a select-fire, straight blowback-operated weapon that fires from the closed bolt position. The cartridge used produces a very low recoil impulse and this enables simple unlocked blowback operation to be employed; there is no delay mechanism and the cartridge is supported only by the inertia of the bolt and the strength of the return springs. When fired, gas pressure drives the case back in the chamber against the resistance provided by the weight of the bolt and its two recoil springs. The bolt travels back, extracting the empty case which is then ejected straight upwards through a port in the receiver housing top cover.
The Škorpion’s compact dimensions were achieved by using a telescopic bolt assembly that wraps around a considerable portion of the barrel. The weapon features a spring-loaded casing extractor, installed inside the bolt head and a fixed, double ejector, which is a protrusion in the weapon’s frame.
As the bolt is relatively light, an inertial rate reducer device housed inside the wooden pistol grip lowers the weapon’s rate of fire from 1,000 rounds/min to a more manageable 850 rounds/min. The rate reducer operates as follows: when the bolt reaches the end of its rearward stroke it strikes and is caught by a spring-powered hook mounted on the back plate. At the same time it drives a lightweight, spring-loaded plunger down into the pistol grip. The plunger is easily accelerated and passes through a heavy weight which is left behind because of its inertia. The plunger, having compressed its spring, is driven up again and then meets the descending inertia buffer. This slows down the rising plunger which, when it reaches the top of its travel, rotates the hook, releasing the bolt which is driven forward by the compressed recoil springs.