The Heckler & Koch HK33E was developed for the export market as an off-shoot of the HK33 family of automatic weapons (the "E" in the designation standing for "Export"). The new rifle carried much of the form and function of the original including the internal roller-locked blowback system of operation (developed for the HK G3 rifle). It was given minor improvements including a reinforced stock, support for a bipod assembly under the forend. Selective fire was possible.
Chambered for the 5.56x45mm NATO cartridge, the weapon was regarded as accurate under full-automatic fire, achieving over 700 rounds per minute. Feeding was from a 30-round detachable box magazine. Through-and-through, the HK33E was nothing more than the G3 weapon chambered for the 5.56x45mm NATO cartridge.
Several major forms of the rifle emerged including the base assault model with fixed stock, a version with a retractable butt, one fitted with a bipod for the support fire role, a precision model for use in the Designated Marksman / Sniper rifle and a short-barreled carbine offering, the latter designated as "HK33KE".
Operators of the series became Brazil, Greece, Ireland (Army Rangers), Malaysia (special units), Myanmar, Mexico, Portugal, Saudi Arabia, Turkey (local production by MKEK) and the United Kingdom (SAS).