The CETME rifle was a Spanish battle rifle designed by Ludwig Vorgrimmler and produced by CETME. Itself developed from the German StG 45(M), the CETME rifle served as the basis for the Heckler & Koch G3.
Shortly after the establishment of the Spanish state-owned arms factory CETME in 1949, ex-Mauser engineer Ludwig Vorgrimmler emigrated there to continue development of the prototype StG.45(M), which had been designed shortly before World War II ended. CETME agreed to take on the design with Vorgrimmler heading the project. A series of prototypes were created in a variety of different calibers, including the German intermediate cartridge, 7.92×33mm Kurz, and the Russian rimmed cartridge, 7.62×39mm. Eventually CETME settled on the 7.62×51mm NATO cartridge after it became standardized across Europe in the 1950s. Initial prototypes were known as the Model A.
By 1957, the rifle was improved as the Model B and was tested by the Spanish Army, who selected it as their new standard-issue service rifle. The same year, CETME sold production rights of the weapon to Heckler & Koch in West Germany, who produced their own version known as the G3, which became a popular battle rifle during the Cold War. The design was finalized as the Model C in 1964, which superseded production of the Model B.
By the 1970s, the 7.62×51mm had begun to fall out of favor and the 5.56×45mm cartridge became the new NATO standard. In response, CETME updated the design in the form of the rechambered Model L, which sported a sleeker aluminium finish and scaled-down mechanism. The Model L replaced the Model C as the Spanish service rifle in 1987 and was itself replaced by the Heckler & Koch G36 in 1999.
The CETME rifle pioneered the roller-delayed blowback mechanism, designed by Vorgrimmler for the StG.45(M). The heavy two-part bolt is inclined at the bolt face and operated by two rollers which accelerate the movement of the bolt. When the gun is fired, the rollers push down on either side of the inclined bolt, forcing it backward. While the bolt travels back, the empty casing is ejected and a new round is chambered during the bolt's return. The chamber is fluted to prevent the cartridges from getting caught and causing a jam. The rifle fires from an open bolt in automatic fire and a closed bolt when switched to semi-automatic.
The Model A was the first production version of the rifle, designed in 1955. It was chambered for 7.62×51mm CETME, which was dimensionally similar to the NATO cartridge but used a smaller projectile and propellant. The cartridge was found to be underpowered and rejected in favor of the standardized NATO round.
The Model B succeeded the Model A in 1957. It was basically identical in design but could be chambered for either the NATO or CETME cartridge. The Model B was accepted into service with the Spanish Army and was their standard-issue rifle until it was phased out by the Model C in the 1960s.
The Model C a detail improvement of the Model B developed in 1964. It was made from strengthened steel to support the 7.62×51mm NATO cartridge, as it no longer could be chambered for the CETME cartridge, which by the 1960s had become obsolete. The aluminium furniture of the Model B was replaced with wooden components. Production of the Model C began in the mid-1960s and lasted until 1976.
The Model E was a cheaper variant of the Model E that utilized aluminium pressings instead of steel parts. The wooden furniture of the Model C was also replaced. The Model E was made to a lower standard than the Model C and was only produced for a short period.
The Model L was an improved and updated version of the Model C, re-chambered for 5.56×45mm NATO. It replaced the Model C in Spanish service in the 1980s.