Sa vz. 23

The CZ Model 25 (properly, Sa 25 or Sa vz. 48b/samopal vz. 48b – "samopal vzor 48 výsadkový", "submachine gun model year 1948 para") was perhaps the best known of a series of Czechoslovak designed submachine guns introduced in 1948. There were four generally very similar submachine guns in this series: the Sa 23, Sa 24, Sa 25, and Sa 26. The primary designer was Jaroslav Holeček (1923–1977), chief engineer of the Česká zbrojovka Uherský Brod arms factory.
Design.
The Sa 23 series utilize a straightforward blowback action, with no locked breech, and fire from the open bolt position. They also use a progressive trigger for selecting between semi-automatic fire and fully automatic fire. Lightly pulling on the trigger will fire a single shot. Pulling the trigger farther to the rear in a continuous motion will fire fully automatically, until the trigger is released or the magazine is empty.
The Sa 23 series were submachine guns with a telescoping bolt, in which the forward part of the moving bolt extends forwards past the back end of the barrel, wrapping around that barrel. This feature reduces the required length of the submachine gun significantly and allows for better balance and handling. Handling was further improved by using a single vertical handgrip housing the magazine and trigger mechanism, roughly centered along the gun's length. The gun's receiver was machined from a single circular steel tube.
The design of the Sa 23 series submachine guns is most notable in the West for having inspired the open-bolt, blowback-operated, telescoping bolt design of the slightly later Uzi submachine gun.
Variations.
The Sa 24 and Sa 26 were introduced after Czechoslovakia joined the Warsaw Pact, and were redesigned to fire 7.62×25mm Tokarev standard Soviet type pistol ammunition.
Usage.
The Sa 23 and 25 models were used by Cuba during the 1960s and 70s, and some can be seen in photos of the Bay of Pigs invasion.
After the Sa 25 was declared obsolete in 1968, many of the 9mm weapons were sold around the world. The surplus weapons were exported to other communist countries including North Vietnam. A somewhat-modified copy of the 9×19mm Parabellum model was produced in Rhodesia in the early 1970s as the LDP and given the nickname "Rhogun". Manufacture was later transferred to South Africa where it was briefly marketed as the Sanna 77 in semi-automatic fire only.