Century Arms produced many of these C91 rifles starting around 2006. They made these rifles into the 2010’s. Some rifles used surplus parts kit and others used more US parts. The rifle resembles an HK-91 and is a semi-automatic build using surplus components.
The Heckler & Koch G3 (Also known as Gewehr 3) is a 7.62x51mm NATO Battel rifle developed in the 1950s by the German H&K in collaboration with the Spanish state-owned factory Centro De Estudios Tecnicos de Materiales Especialses CETME. The design actually came to be shortly after the Second World War and was developed heavily by CETME of Spain. Before the fall of Germany and Mauser Oberndorf the German developed a prototype assault rifle chambered in 8mm Kurz known as the Gerat 06 which utilized a roller locking short recoil system, which was adapted from the MG-42. This rifle later went on to become the lesser-known STG 45 (Sturmgewehr 45) and was not produced enough by the time the war ended.
The same German engineers involved in the STG-45 project went on to work at France for CEAM. Ludwig Vorgrimler and Theodor Loffler modified the design and chambered three rifles in .30 Carbine, 7.92×33 Kurz, and 7.65×25 French. Manufacture d’Armes de Chatellerualt and Saint-Etienne tested many of these prototypes. However France had to cancel their adoption and study of these new weapons due to financial reasons and the Indochina War. That is when in 1950 Vorgrimler moved to Spain to create the LV-50 rifle and made versions in 7.92x40mm CETME. The rifle was renamed the Modelo 2 and gained much attention from the West German Bundesgrenzschutz. The Germans required the 7.62x51mm cartridge to meet NATO specifications and had help from H&K. HK produced the CETME Model B which received some modifications from the model A. It was able to fire from a closed bolt and added much ergonomics like a folding bipod, 22mm rifle gernande launcher guide, and sleeker design. It was adopted in 1958 by the Spanish Army as the famous CETME Modelo 58 aka CETME C.
The Bundesgrenzschutz canceled their order for the CETME rifles as they adopted Belgian made FN FAL rifles designated (G1) Gewehr 1 and even purchased from SIG Switzerland Neuhausen 510 rifles as the (G2). However the West German Army (Bundeswehr) were very interested in the CETME rifles and purchased many. Eventually the German government chose the CETME design but required that the G3 rifle needed to be produced under license in Germany, FN could not compete as they did not want to let the Germans produce G1 FAL rifles. Rheinmetall and Heckler and Koch were assigned production rights and began producing rifles for the German Army. Interestingly enough Rheinmetall gave up the right to produce G3 rifles in 1969 to HK in exchange that HK would not bid on the MG3 machine gun production. Eventually in 1977 the West German government gave HK ownership of G3 production and sales rights, and they were the exclusive manufacturer. HK would need to pay the government 4 Marks per rifle even after being awarded the rights.
The G3/HK91 utilizes a roller delayed blowback operation system. It is a two piece bolt that has a bolt head and carrier. The bolt is locked in battery with two steel rollers that lock intro the recess of the barrel trunnion. The bolt cams from rearward pressure of expanding gases upon the bolt head and unlock the bolt and carrier . Many people like the roller locking action because it is very reliable and does not need to be adjusted because it uses the mass of the operating system against the power of the cartridges gases.
The HK91-G3 is one of the most famous rifles in the world. It really was a competition in the West between the FN Fal and the H&K G3 for most popular battle rifle. Countries like Norway, Sweden, Denmark, Iceland, United Kingdom, Greece, Portugal, Turkey, Rhodesia, Zambia, South Africa, Columbia, Saudi Arabia, Mexico, and Iran all adopted the G3 and either built licensed copies or placed direct orders through HK. The Germans replaced the G3 with the G36 rifle but the G3 remains in service by other nations around the world today.