The Heckler & Koch HK433 is a modular assault rifle chambered for 5.56×45mm which combines features of the G36 and the HK416 families of assault rifles. The HK433 was designed by Heckler & Koch to be familiar to operators with experience using the Heckler & Koch G36 and HK416 platforms. All controls are ambidextrous, and major components are modular, allowing for rifles to be configured in the field as needed. History The HK433 was first introduced at EnforceTac 2017 which went on the 1st and 2 March in Nürnberg, Bavaria, Germany, after the HK433 was shown to a select number of people at the earlier SHOT Show in January. Heckler & Koch offered the HK433 along with the HK416 as a candidate for the German Bundeswehr's competition to select a new assault rifle. The HK G36, the Bundeswehr's standard assault rifle since 1997, is to be phased out and a replacement is planned to be phased in from 2020. Design The HK433 has multiple barrel lengths ranging from 11-, 12.5-, 14.5-, 16.5-, 18.9- or 20-inch. All of the barrels are cold hammer forged, hard chrome lined with a 178 mm (1 in 7 inch) right-hand twist, six-groove rifling. It features a short-stroke gas piston driven system similar to the Heckler & Koch G36 and HK416, with a gas block regulator adjustment located above the barrel. The non-reciprocating charging handle can be changed to operate from either side of the forestock of the rifle, but does not have a locking recess like the Heckler & Koch G3 family of weapons. All other primary controls are ambidextrous. It has an interchangeable barrel system and a folding adjustable buttstock with a three position cheek riser and a paddle-style magazine release. Side-folding the buttstock shortens the HK433 by . The monolithic upper receiver is made of aluminium alloy, and the lower receiver is made of polymer. The HK433 features a STANAG 4694 NATO Accessory Rail at 12 o'clock that is backwards-compatible with the STANAG 2324/MIL-STD-1913 Picatinny rail. At 6 o'clock it features the STANAG 2324/MIL-STD-1913 Picatinny rail. At the 3- and 9-o'clock positions the proprietary "HKey" accessory attachment system is used instead of the more commonly used M-LOK or KeyMod systems. The empty weight of a HK433 Draft STANAG 4179 compliant box magazine is approximately . Models Currently are 3 variants of the HK433 and 2 variants of the HK437 available: Users : Schleswig-Holstein