Heckler&Koch HK 33 and HK 53 (Germany)

Caliber:5.56x45mm(.223 Rem) HK33, 5.56x45mm (.223 Rem) HK33K, 5.56x45mm (.223 Rem) HK53

Length: 919 mm - 740 mm with retracted stock in A3 variant, 865 mm - 670 mm with retracted stock in A3 variant, 780 mm - 590 mm with retracted stock in A3 variant

Barrel length: 390 mm, 322 mm , 211 mm

Weight empty: 3.9 kg, 3.65 kg, 3.0 kg

Magazine capacity: 25, 30, 40 rounds HK33, 25, 30, 40 rounds HK33K, 25, 30, 40 rounds HK53

Rate of fire: 750 rds/min, 750 rds/min, 750 rds/min

HK33 had been developed by the German company Heckler and Koch in mid- to late 1960s as a scaled-down version of their G3 battle rifle, and entered production in 1968. HK33 was developed for then-new cartridge, 5.56x45mm (.223 Remington), and while it had not been adopted by German military, it saw significant use by some West Germany police and security units, and also widely exported, and used by Malaysia, Chile and Thailand armed forces. 

Since 1999, HK33 also manufactured under license in Turkey. HK33 is still in production in Germany by HK, and also served as a platform for further developments, such as G-41 assault rifle and HK53 compact assault rifle (known by the HK as submachine gun).

HK53 is a ultra-compact version of HK33, which advertised by HK as "submachine gun" and, by common sense, falls in the same category as soviet AKS-74U or Colt "Commando". All these guns can be classified as "compact (or short) assault rifles" by the fact, that they are used the intermediate rifle round. Hk53 was developed in mid-1970s and is still in production and offered for export.

HK33 is a delayed blow back operated, selective fire rifle, that utilized two pieces bolt with two rollers that used to delay bolt blow back. The receiver is made from stamped steel, and HK33 is available with either a polymer fixed butt stock (HK33A2) or retractable metallic butt stock (HK33A3). Carbine version of the HK33 also available and featured shorter barrels and similar fixed or retractable stocks (HK33KA2 and HK33KA3, respectively).

All HK33 variants available with different trigger units, with or without 3-rounds burst mode. HK's proprietary claw-type mounts allow telescopic sights to be mounted on any version of HK33. Full-length HK33s can be equipped with bayonet or under barrel 40mm grenade launchers, HK79A1, also made by Heckler & Koch. Full-length HK33 rifles also can launch rifle grenades from combined muzzle compensator/flash hider. All HK33 and HK53 guns are equipped with drum-type rear sights.

HK53 is internally similar to the HK33 but cannot fire rifle grenades nor mount under barrel 40mm grenade launcher .HK53 also cannot be equipped with bayonet, and featured long, four-prong flash hider.

Both HK33 and HK53 can use 25, 30 and 40 round box magazines, but latter are out of production by HK for some time.