HK433

The Heckler & Koch HK433 is a modular assault rifle chambered for 5.56x45mm NATO that deliberately combines features of the G36 and HK416 families. It was shown to a select audience at SHOT Show in January 2017 and formally introduced at EnforceTac in Nuremberg that March. Heckler & Koch offered it alongside the HK416 as a candidate in the German Bundeswehr's System Sturmgewehr Bundeswehr competition to replace the G36, the standard German service rifle since 1997.

The design goal was familiarity: an operator trained on the G36 or HK416 should be able to pick up an HK433 without relearning it. All controls are ambidextrous and the major components are modular, so a rifle can be reconfigured in the field. Six barrel lengths are offered - 11, 12.5, 14.5, 16.5, 18.9 and 20 inches - all cold hammer forged, hard chrome lined with six-groove rifling at a 178 mm right-hand twist. The action is a short-stroke gas piston system in the manner of the G36 and HK416, with the gas regulator sitting above the barrel. The non-reciprocating charging handle can be set up on either side of the forestock. The upper receiver is a monolithic aluminium alloy unit and the lower is polymer, offered with a choice of two magazine releases: an AR-15 style button or a G36-style paddle. The buttstock folds to the side, shortening the weapon by 266 to 297 mm, and is adjustable with a three-position cheek riser.

The rail layout reflects the shift in accessory standards during the rifle's development. At 12 o'clock it carries a STANAG 4694 NATO Accessory Rail that remains backwards compatible with MIL-STD-1913 Picatinny; at 6 o'clock it has a conventional Picatinny rail; and at 3 and 9 o'clock the proprietary HKey system used on early rifles has been replaced by the now-standard M-LOK. The HK437, announced alongside the HK433, is chambered in .300 AAC Blackout with 7- and 9-inch barrels.

German adoption has come through the HK437 rather than the base rifle. The Bundeswehr ordered 988 HK437s for the KSK special forces, designated the G39, and in October 2022 the Schleswig-Holstein state police procured more than 200 rifles and accessories for 1.68 million euros; in 2024 that force announced its intention to replace all its SIG MCX and MP5 weapons with up to 1,700 HK437s by 2026. The Main Directorate of Intelligence of Ukraine is also an operator, and the HK433 has been discussed as a potential successor to the British L85.