Star Model Z84

The Star Z-84 was a Spanish selective-fire submachine gun originally manufactured by the now defunct Star Bonifacio Echeverria, S.A.. The Z-84 is a sturdy, well-designed weapon that never saw high production due to politics. Originally manufactured for use by SCUBA divers, the Z-84 could be used right out of the water without any need to drain the working parts or magazine, known as over-the-beach or OTB capability.
Star S.A. developed the weapon after a successful run of submachine guns based on the German MP-40 design. Realizing they couldn't rebuild the same weapon over and over, they built the Z-84 completely from scratch using modern designs and engineering. Chief designer of Z-84 was Eduardo Iraegui.
At the time of the Z-84's design, Star was building and exporting large numbers of cheap handguns to the US. The 1994 Assault Weapons Ban (now repealed), banned the importation of many of their designs. This proved disastrous for Star and other Spanish gunmakers, and by 1996 had driven them into bankruptcy. 
Fewer than 1,000 Z-84s were manufactured before the company went bankrupt, but many were sold on a testing basis to various countries in South and Central America. Iranian Takavar commandos still use the Z-84 as it is found to be reliable in amphibious warfare.
Early development.
The Z-75 was Star's modern, 3rd generation, SMG chambered in 9mm Largo. It superficially resembled the UZI, and incorporated the modern features first seen on the Czechoslovakian Sa vz. 23, such as an overhanging bolt, to reduce overall length. The receiver was of stamped steel, with a square-section bolt riding on rails internally. It fired from an open bolt in the same method as the earlier weapons used, and had the same 20 cm (7.85 in) barrel length. It weighed 2.6 kg (5.75 lb) unloaded.
The Z-75 was a commercial development project that led to the almost identical Z-84 and the Z-75 never went on mass production.
Overview.
The Z-84 is a 9mm Parabellum, blowback operated, selective-fire, capable of fully automatic firing, open bolt weapon which heavily derives from Z-75. Having very few moving parts makes it a very simple weapon to operate and maintain. Made mostly of stamped and cast parts, little machining is needed to produce the weapon. It uses an "overhung" bolt meaning the bolt actually rides forward over the barrel for 3". This allows a shorter overall length while maintaining a long barrel for better accuracy. First pioneered in the Czechoslovakian Sa vz. 23 submachine gun, the overhung bolt had become a fixture in many of today's modern designed SMGs, being employed in firearms such as the Israeli UZI and Italian Beretta M12.
A sturdy folding metal stock helps the weapon gain accuracy when fired from the shoulder, and has a safety switch on the trigger. The sights are protected by large steel ears and are adjustable; the rear sight is a diopter sight with 100 and 200 meter settings and the front is adjustable for windage and elevation.
Variants.
There are two variants of the weapon: