How a Heckler & Koch HK33 Rifle Works

Wikipedia: The Heckler & Koch HK33 is a 5.56mm assault rifle developed in the 1960s by West German armament manufacturer Heckler & Koch GmbH (H&K), primarily for export.

Building on the success of their G3 design, the company developed a family of small arms (all using the G3 operating principle and basic design concept) consisting of four types of firearms: the first type, chambered in 7.62×51mm NATO; the second, using the Soviet 7.62×39mm M43 round; the third, chambered in .223 Remington and 5.56×45mm NATO; and the fourth type, chambered for the 9×19mm Parabellum pistol cartridge. Commercially the HK33 was a successful design but it did not sell as well as the G3.

The HK33 series of rifles were adopted by the Brazilian Air Force (Força Aérea Brasileira or FAB), the armed forces of Thailand and Malaysia where they were produced under a licence agreement. The rifle was also licence-built in Turkey by MKEK, and exported from France branded as MAS but actually made in Germany.

The HK33 is a selective fire weapon with Heckler & Koch's roller-delayed blowback system of operation. It employs a two-piece bolt consisting of a bolt head with a pair of rollers and bolt carrier. Upon firing, the two cylindrical rollers in the bolt head are cammed inward by inclined surfaces of the barrel extension and impart a rearward motion on the locking piece, which also propels the bolt carrier rearward. This built-in mechanical disadvantage delays the movement of the bolt head relative to the bolt head carrier which is withdrawing at significant higher velocity of the bolt head. The rollers soon compress entirely into the bolt head, clearing the locking recesses of the barrel extension, and both parts now continue rearward together, opening the breech and actuating the extraction and feeding cycles. The chamber is opened under high pressure, thus the chamber received a series of flutes in order to increase extraction reliability and prevent sticking of the spent casing to the chamber walls.

Type Assault rifle
Place of origin West Germany
Service history
In service 1968–present
Used by See Users
Wars

Vietnam War
Araguaia Guerrilla War
Salvadoran Civil War
Lebanese Civil War
Kurdish–Turkish conflict
Internal conflict in Myanmar
Cenepa War
South Thailand insurgency
Insurgency in Northeast India[2]
Militias-Comando Vermelho conflict

Production history
Manufacturer Heckler & Koch,
MKEK (licensed)
Produced 1968—2000 (H&K)
1999—present (MKEK)
Variants See Variants
Specifications
Mass HK33A2: 3.65 kg (8.05 lb)
HK33A3: 4.0 kg (8.8 lb)
HK33KA3: 3.9 kg (8.6 lb)
HK53: 3.05 kg (6.7 lb)
Length HK33A2: 920 mm (36.2 in)
HK33A3: 940 mm (37.0 in) stock extended / 735 mm (28.9 in) stock collapsed
HK33KA3: 865 mm (34.1 in) stock extended / 675 mm (26.6 in) stock collapsed
HK53: 755 mm (29.7 in) stock extended / 563 mm (22.2 in) stock collapsed
Barrel length HK33A2: 390 mm (15.4 in)
HK33KA3: 332 mm (13.1 in)
HK53: 211 mm (8.3 in)
Cartridge .223 Remington
5.56×45mm NATO
Caliber 5.56mm
Action Roller-delayed blowback
Rate of fire HK33A2: 750 rounds/min
HK53: 700 rounds/min
Muzzle velocity HK33A2: 950 m/s (3,117 ft/s)
HK33KA3: 880 m/s (2,887.1 ft/s)
HK53: 750 m/s (2,460.6 ft/s)
Effective firing range 200–400 m (219–437 yd) sight adjustments
600 metres (656 yd) with Fero Z24-G telescopic sight
Feed system 25-, 30-, or 40-round detachable box magazine
Sights Rotary rear aperture drum, hooded foresight.