At the end of World War 2, German engineers were working on perfecting a new breed of service rifle known as the "assault rifle". The assault rifle immediately antiquated the bolt-action service rifle as the standard-issue firearm of any modern army. The new weapon allowed use of a rifle-caliber cartridge in a more compact body with the capability of repeat, automatic fire at targets within short and medium ranges - ranges most often being encountered by infantry. The most famous early example of this type of weapon became the German wartime StG 44 (Sturmgewehr 44 or "Storm Rifle") - often cited as the "Father of Assault Rifles" - which led to a more refined and simpler prototype - the StG 45. Unfortunately for the Germans, the StG 45 only existed in prototype form before the end of the war in May of 1945 and perhaps as little as 30 units were produced.
The StG 45 made use of the intermediate 7.92x33mm Kurz ("short") cartridge though, perhaps most importantly, it brought about the use of the "roller-delayed blowback" firing principle. This operation essentially involved two locking rollers situated to either side of the firing pin near the base of the cartridge, engaging the sides of the receiver during the firing action and delaying the movement of the bolt head - the barrel remaining fixed in place. The principle was adopted as a cost-effective alternative to a proposed gas-operated, roller-locked breech system originally intended for the StG 45. The end of the war stymied development of the StG 45 but German engineers, having relocated to Spain after the war, began perfecting the system under the government-sponsored Centro de Estudios Tecnicos de Materiales Especiales ("Technical Studio of Special Materials") otherwise known as CETME. The engineers managed to produce a more refined and reliable roller-delayed blowback system chambered for the 7.92mm cartridge and marketed it towards the West German Army for consideration as their new standard-issue service rifle. The West German Army favored the CETME idea but preferred a weapon utilizing the 7.62x51mm NATO standard cartridge instead. CETME engineers continued their work on the design and ultimately produced the CETME "Model 58" assault rifle/battle rifle firing a reduced-charge 7.62mm cartridge (to become the 7.62x51mm CETME).
After evaluation of competing systems, the West German Army selected the CETME design as their new standard-issue assault rifle. License-production of the weapon was obtained and the firm of Heckler & Koch revised the CETME system to accept the full-power 7.62x51mm NATO cartridge. The resulting design became the HK G3 series ("Gewehr 3") automatic rifle/battle rifle series which made use of sheet metal stampings in its construction dotted by furniture manufactured of plastic. The internal firing mechanism was a much more refined form of the original StG 45 roller-delayed blowback system and the overall construction of the rifle budget-friendly. The G3 shared much with the Spanish CETME but was, for all intents and purposes, its own evolution of the Stg 45 before it - a fairly straightforward, basic unassuming rifle formally categorized as a "Battle Rifle" due to its use of a full-power rifle cartridge. The HK G3 was introduced in 1959 and became the standard-issue service rifle of the West German Army. Some early HK G3s were, however, known to feature "CETME" stamped along their receivers, at least up until 1961.
At its core, the HK G3 was a fine, if unspectacular, automatic rifle development exhibiting lines that would become a standard for the HK concern for decades to come. It yielded a very utilitarian appearance but was a fully-functional end-product worthy of the rigors of the modern battlefield. The design incorporated a solid fixed stock with an angled pistol grip near the thumb-operated fire selector (safety, semi-automatic single-fire and full-automatic fire modes). The curved trigger unit was held within a hardened trigger guard. Ahead of the trigger lay the magazine well which accepted a 20-round detachable box magazine. The magazine release catch was aft of the magazine well. The receiver largely incorporated long-running horizontal lines from front to rear. The forestock consisted of a plastic handguard shrouding a good length of the barrel which protruded a distance away and was capped with a slotted muzzle flash hider. There was a rear sighting installation atop the receiver (the identifiable "drum-type" diopter sight) with the front sight added at the extreme end of the forestock. Overall, the G3 served as a very clean, "no frills" gun design.
The designator "G3" was used to simply mark the initial production models which were noted for their wooden shoulder stocks and flip over rear sights. The G3 followed much of the form and function of the preceding Spanish CETME Model B rifle marks and these were then followed into service by the HK GA1 which incorporated a retractable buttstock. The HK G3A2 mark were simply G3 service rifles with a standardized rotary rear sight installation.
The HK G3A3 became the final production form of the G3 family line and its most definitive mark. The G3A3 utilized the rotary rear sight unit of the G3A2 models with a revised front sight and fixed plastic shoulder stock. Additionally, this version also saw its flash hider upgraded to a "prong" type. A bipod was optional for stabilized sustained fire. This version weighed in at 9lbs, 11oz with a 40 inch overall length and 17.7 inch barrel. Cyclic rate-of-fire was 550 rounds per minute with a muzzle velocity of 2,625 feet per second. The G3A3A1 incorporated a brass ejection port deflector and ambidextrous firing selector.
The HK G3A3 series itself spawned several notable sub-variants related to the G3 breed. This included the G3A3ZF ("Zielfernohr") which introduced receiver support for an optics installation (the Hensoldt 4x24 power scope). This essentially allowed the G3 to be used as a long-range "sniping" weapon firing a full power cartridge and formed the basis of more dedicated sniper platforms. The G3A4 brought about use of a collapsing stock - which greatly reduced the weapon's overall length - as well as scope support. The similar G3A4A1 included the brass ejection port deflector and ambidextrous fire selector control. The G3KA4 was a compact carbine variant with a collapsible stock. The G3KA4A1 was similar though with the brass ejection port deflector and ambidextrous fire selector. G3A5 designated G3A3 models produced in Denmark (as the Gv M/66).
The G3SG/1 was an accurized version of the G3 intended for dedicated sniper use within the inventory of the West German Army. This variant utilized a standard scope, folding bipod, cheekpiece at the shoulder stock and specialized trigger unit. A revised scope G3 was the MSG3. The G3TGS incorporated the HK79 series 40mm grenade launcher under the forend. Scoped G3s eventually gave rise to the refined PSG-1 sniper rifle series (intended for police forces) which sported a more powerful scope, standard ergonomic comforts, a free-floating barrel and available in semi-automatic fire only. The high cost of the PSG-1 rifle led to the more economical (and militarized) MSG-90.
G3A3s produced under license in Luxembourg, Iran and Turkey were designated as HSG1, G3A6 and G3A7 respectively. Iran developed a "bullpup" G3 version as the DIO G3, the integral working components and magazine now set to the rear of the trigger group. The collapsing stock version (G3A4) was also produced in Turkey, though as the G3A7A1. Denmark leased G3 rifles as the Gv M/75. A locally-produced Norwegian version of the G3A5 was the AG-3. The AG-3F1 was the collapsible stock form and AG-3F2 was an improved form. Sweden produced the G3A3 as the Ak 4. Scoped versions were the Ak 4OR and Ak 4B. Pakistan locally-produced the G3A4 as the G3P4.
The G3 went on to serve as the basis for a whole family of weapons related to the original G3 line. The HK41 was a police/civilian version with semi-automatic fire only. Similarly, HK produced the HK91 in semi-automatic fire for civilian consumption. The HK911 followed the HK91 in an effort to comply with US firearms restrictions. Similarly, the SR9 followed in the SR9 (T) and SR9 (TC) sporting guises. Other forms under non-HK designations have emerged since the types importation into the lucrative US gun market - these applied by various importing companies.
The HK G3's reach cannot be overstated for it has seen widespread use (not to mention license production in some parts) across Argentina, Angola, Bahrain, Bangladesh, Bolivia, Brunei, Burkina Faso, Burma, Burundi, Chad, Chile, Colombia, Ivory Coast, Croatia, Cyprus, Djibouti, Dominican Republic, El Salvador, Estonia, Ethiopia, Gabon, Ghana, Greece, Guyana, Haiti, Iceland, Indonesia, Iraq, Jordan, Kenya, Latvia, Lebanon, Libya, Lithuania, Malawi, Malaysia, Mauritania, Mexico, Morocco, Myanmar, Niger, Nigeria, Norway, Paraguay, Peru, Philippines, Portugal, Qatar, Rhodesia, Rwanda, Saudi Arabia, Senegal, Somalia, South Africa, Sudan, Tanzania, Togo, Uganda, United Arab Emirates, Zaire, Zambia and Zimbabwe in addition to the previously mentioned nations. Since its introduction in 1959, the G3 still continues service today and has seen countless combat actions in a myriad of localized and large-scale wars. It formed a standard-issue NATO assault rifle for decades.
Production has been undertaken by Heckler & Koch, Rheinmetall, SEDENA, DIO, FBP, Carl Gustafs, Husqvarna, Hellenic Arms Industry, Kongsberg Vapenfabrikk, MAS, Military Industry Corporation, MKEK, Paksitan Ordnance Factories and Royal Ordnance PLC. Such global exposure was attributed to the fact that the G3 was, in fact, much more economically-friendly that other competing automatic rifles of the time - namely the Belgian FN FAL and the American M14.
For the unified German Army, the G3 ceased frontline operational use in 1997, giving way to the HK G36 family line.