I stand corrected:
http://matrix.dumpshock.com/raygun/firearms/assault/g3ka4.html:
The genesis of the G3 (Gewehr or Rifle) Battle Rifle actually took place 14 years prior to its adoption and initial production by Heckler & Koch GmbH.
During WWII, an engineering team at Mauser headed by Ludwig Vorgrimler adapted a roller-locking delayed blowback form of operation for use in the second-generation Sturmgewehr (assault rifle), designated StG.45. Succeeding the gas piston-operated StG.44, the StG.45 also fired the 7.92x33mm Kurz cartridge. However, the war was brought to an end before production of the StG.45 could begin in earnest.
After the war, Vorgrimler and several other German engineers eventually resumed development of the roller locking design at the Centro de Estudios Tecnicos de Materiales Especiales (CETME), Spain's small arms development center located in Seville. The rifle was designed around an experimental 7.92x40mm cartridge.
When the American 7.62x51mm T65 cartridge was standardized by NATO in 1954, the German Bundesgrenzschütz (Federal Border Guard) tested several 7.62x51mm-chambered rifles, including the Fabrique Nationale FAL (G1), the SIG SG510 (G2), the CETME Modelo A (G3), and the Armalite AR-10 (G4). Out of these, the FN FAL was accepted for service as the G1. However, Fabrique Nationale would not license post-war Germany to produce the FAL. The CETME rifle was then chosen to replace the G1. A manufacturing license was transferred from the Dutch NVM company to Heckler & Koch and production began in 1959.
The legendary G3 Battle Rifle has been used by more than 50 nations since its introduction, including Germany, Greece, Iran, Mexico, Norway, Pakistan, Portugal, Sweden and Turkey. It was the official infantry rifle of the German Bundeswehr from 1959 to 1995, when it was replaced by another Heckler & Koch rifle, the G36. As of 2002, Heckler & Koch have ceased production of the G3A3 rifle.
Designed for paratroopers and vehicle crews, the G3KA4 differs from the G3A3 by including a shortened 12.4" (315mm) barrel and a retractable shoulder stock. Due to its modular design, many options are available for the G3A3 and other HK roller-locked weapons.