G3 Rifle by Montanau on DeviantArt (original) (raw)
The G3 (Gewehr 3) is a 7.62x51mm NATO, selective-fire battle rifle developed in the 1950s by the German armament manufacturer Heckler & Koch (H&K) in collaboration with the Spanish state-owned design and development agency CETME (Centro de Estudios Técnicos de Materiales Especiales). The G3 was the service rifle of the Bundeswehr until it was replaced by the Heckler & Koch G36 assault rifle in the 1990s.
The origin of this rifle can be traced back to the final years of World War 2 when Mauser engineers at the Light Weapon Development Group (Abteilung 37) at Oberndorf am Neckar designed the Maschinenkarabiner Gerät 06 (MKb Gerät 06, "machine carbine device 06") prototype assault rifle chambered for the intermediate 7.92x33mm Kurz cartridge, first with the Gerät 06 model using a roller-locked short recoil mechanism originally adapted from the MG-42 machine gun but with a fixed barrel and conventional gas-actuated piston rod. With careful attention to the mechanical ratios, the gas system could be omitted. The resultant weapon, Gerät 06H (the "H" suffix is an abbreviation for halbverriegelt - "half-locked") was assigned the designation StG-45(M) (Sturmgewehr 45(M) , assault rifle 45) but was not produced in significant numbers and the war ended before the first production rifles were completed.
The G3 is a selective-fire automatic weapon that employs a roller-delayed blowback operating system. The two-piece bolt assembly consists of a breech (bolt head) and bolt carrier. The bolt is held in battery by two sliding cylindrical rollers that engage locking recesses in the barrel extension. The breech is opened when both rollers are compressed inward against camming surfaces driven by the rearward pressure of the expanding gases upon the bolt head. As the rollers move inward, recoil energy is transferred to the locking piece and bolt carrier which begin to withdraw while the bolt head slowly moves rearward in relation to the bolt carrier. As the bolt carrier clears the rollers, pressure in the bore drops to a safe level, the bolt head is caught by the bolt carrier and moves to the rear as one unit, continuing the operating cycle. Based on the geometric relationship arising from the angles of the roller contact surfaces of the locking piece and the barrel extension recesses, the recoil of the bolt head is delayed by a ratio of 4:1 for the 7.62×51mm NATO chambering. Thus during the same period of time, the bolt head carrier moves 4 times faster than the bolt head. This ratio is continued until the locking rollers have been withdrawn from the barrel extension recesses. The bolt features an anti-bounce mechanism that prevents the bolt from bouncing off the barrel's breech surface. The "bolt head locking lever" is a spring-loaded claw mounted on the bolt carrier that grabs the bolt head as the bolt carrier group goes into battery. The lever essentially ratchets into place with friction, providing enough resistance to being re-opened that the bolt carrier does not rebound. The spring-powered claw extractor is also contained inside the bolt while the lever ejector is located inside the trigger housing (actuated by the recoiling bolt).
The G3 is a modular weapon system. Its butt-stock, fore-stock and pistol-grip/fire-control assembly may be changed at will in a variety of configurations (listed below). Simple push-pins hold the components in place and removing them will allow the user to remove and replace parts rapidly. The weapon made extensive use of cost-saving pressed and stamped steel components rather than machined parts and spot welding to connect parts. The stamped sheet metal cocking handle tube and receiver are large exposed parts that are prone to deformation from hard impact as they were designed to be relatively thin to save weight. If dented severely or deep enough during field service reliability problems due to internal parts movement impairments can occur that put the rifle out of action and can not be field solved by the user. To determine and correct such situations armorers are trained to employ specially designed “GO” and symmetry gauges and straightening mandrels to fairly quickly repair such problems.
The original G3 and G3A1 rifle variants had a relatively low iron sights line that consisted of a Klappvisier a "L-type" flip up rear sight and hooded front post. From the G3A2 variant the firearm is equipped with a relatively low iron sight line that consists of a Drehvisier a rotary rear drum and hooded front post. The rear sight is mechanically adjustable for both windage and elevation with the help of tools. This deliberately prevents non-armorers to (re)zero the iron sight line. The rotary drum features an open V-notch (numbered 1) for rapid target acquisition, close range, low light and impaired visibility use and three apertures (numbered 2, 3 and 4) used for: 200–400 metres (219–437 yd) in 100 metres (109 yd) increments for more precise aiming. The 1 V-notch and 2 or 200 metres (219 yd) aperture settings have an identical point of aim. The V-notch and apertures are calibrated for US M80 / German DM111 series or other equivalent 9.5 grams (147 gr) 7.62x51mm NATO ball ammunition. The receiver housing has recesses that work with STANAG claw mounts/HK clamp adapters used to mount day or night aiming optics.