Heckler & Koch HK33

The HK33 is a 5.56 mm assault rifle developed in the 1960s by West German armament manufacturer Heckler & Koch GmbH (HK), primarily for export. Capitalizing on the success of the 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 7.62x51mm NATO, second – using the 7.62x39mm M43 round, third – the intermediate 5.56x45mm caliber and the fourth type – chambered for the 9x19mm Parabellum pistol cartridge.

The HK33 series of rifles were adopted by the Brazilian Air Force (Força Aérea Brasileira, FAB), the armed forces of Thailand and Malaysia where they were produced under a license agreement. The rifle was also license-built in France by MAS, and in Turkey by MKEK. The HK33 is no longer marketed by Heckler & Koch.

Design details
The HK33 is a selective fire delayed blowback-operated weapon. It employs a roller-locked two-piece bolt consisting of a bolt head and bolt carrier. After firing, two cylindrical rollers in the bolt head are cammed inward by inclined surfaces of the barrel extension and locking piece within the bolt carrier under rearward pressure on the bolt head, delaying the bolt’s movement relative to the bolt carrier which is withdrawing at four times the velocity of the bolt head. After the rollers compress into the bolt head clearing the locking recesses of the barrel extension, both parts continue moving back together, opening the breech and operating the extraction and feeding cycle. The breech is opened under very high pressure, to increase extraction reliability the bore chamber is fluted.

The bolt also contains a spring extractor, an anti-bounce device (that prevents the bolt from bouncing after impacting the barrel breech) and a buffer. The lever ejector was placed in the trigger housing (actuated by the recoiling bolt).

The HK33 has a hammer-type firing mechanism.

In the standard version, the rifle comes equipped with an ambidextrous trigger group with a selector lever that is simultaneously the weapon’s safety (it has three positions: “S” or “0” – weapon is safe, “E” / “1” – semiautomatic fire, “F” / “25” – continuous fire). The “safe” setting mechanically disables the trigger. The rifle is fed from 25-round steel magazines weighing 250 g or 40-round aluminum magazines (weighing 157 g). 30-round arch magazines were also introduced for use with the rifle.

The weapon is aimed using adjustable iron sights with a rotating rear drum (corrected mechanically for windage and elevation) that contains a notch used for firing at 100 m and three aperture settings for 200, 300 and 400 m. The receiver top cover has notches permitting the attachment of a clamping mount (standard with the HK33, G3, G3SG/1 and MP5) for use with a telescopic sight (usually a Hensoldt 4x24 scope) or a night vision device.

The barrel is equipped with a closed-type slotted flash suppressor that enables the use of rifle grenades and supports a bayonet.

During its production life the rifle received several minor improvements (these modified weapons are sometimes referred to as the HK33E). The fixed stock was strengthened and the synthetic forearm replaced with a handguard that allows a lightweight bipod to be attached and stowed into two recessed grooves at the base. The shoulder pad in rifles fitted with a telescopic stock was changed to a concave type used thus far in the Heckler & Koch MP5 series. Initially the rifle was produced with a 305 mm (1:12 in) twist rate barrel, which was later upgraded to the faster 178 mm (1:7 in) twist rate (used to stabilize new, heavier NATO standard SS109/M855 ammunition).

Included with the rifle are a detachable bipod, bayonet (from the G3), sling, cleaning kit and a magazine loader. Additionally, the HK33 can be used to mount a 40 mm under-barrel HK79 grenade launcher or a blank-firing adaptor.

Variants
The HK33 is available in several configurations: the HK33A2 (fitted with a rigid synthetic stock), an accurized variant known as the HK33SG/1 (with a telescopic optical sight and improved trigger analogous to the one used in the G3SG/1), HK33A3 (with a telescoping metal stock), the HK33KA3 carbine (barrel reduced in length to the base of the front sight post also equipped with a folding metal stock; the short barrel cannot be used to launch rifle grenades or attach a bayonet) as well as the compact HK53 carbine, which features a short, 211 mm barrel, a forearm derived from the Heckler & Koch MP5 submachine gun and a telescoping stock or a receiver endplate cover (later models also received an open-style flash hider). The HK13 light machine gun was also built based on the HK33. It is fed from either box or drum magazines (the latter has a 100-round capacity), has a quick-change heavy barrel for sustained fire, shrouded with a sheet metal heat guard (replacing the synthetic forearm) and a 2-point bipod adapter.

Heckler & Koch also make a semi-automatic only variant of the HK33A2 for the civilian shooting market designated the HK93.

The rifle is disassembled into the following components for maintenance: the receiver, stock with return spring and trigger pack with pistol grip. The trigger groups can be swapped out to meet the user’s specific mission requirements. HK offers several different trigger assemblies: a three-shot burst fire control group with selector lever/safety (selector settings: “0” – weapon is safe, “1” – single fire, “2” – 2-round burst or “3” – burst, 3-rounds; the selector lever is ambidextrous); a “Navy” trigger unit (three settings: safe, semi and full auto fire) and a four-position trigger group (selector settings: weapon safe, single fire, 3-round burst and automatic fire).

Users

 * Argentina
 * Bosnia and Herzegovina
 * Brazil
 * Chile - Chilean Marines Corps.
 * Cyprus
 * East Timor
 * Ecuador
 * El Salvador
 * France - Police.
 * Greece - Small number in service with the special forces.
 * Ireland - Used by the Garda Síochána.
 * Lebanon
 * Malaysia
 * Mexico - HK53 in use by specialized law enforcement units.
 * Myanmar
 * Peru
 * Spain - Guardia Civil.
 * Thailand
 * Turkey
 * United Kingdom - Small number in service with the Special Air Service and the Police Service of Northern Ireland.
 * United States - Used by various law enforcement agencies. A license-built copy manufactured by Harrington & Richardson known as the T223 was used in small numbers by Navy SEAL teams in Vietnam.
 * Venezuela