# Heckler & Koch HK433

The Heckler & Koch HK433 is a modular assault rifle originally 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.
The Heckler & Koch HK437, chambered in .300 Blackout and featuring 7 and 9 inch barrels, was originally announced along with the HK433 in 2017. In late 2022, the Ministry of the Interior, Municipal Affairs, Housing and Sports of the State of Schleswig-Holstein commissioned Heckler & Koch Germany to manufacture and supply the HK437.

## History

The HK433 was formally introduced at EnforceTac 2017 on 1 and 2 March in Nürnberg, Bavaria, Germany, after having been shown to a select number of people at 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 including 11, 12.5, 14.5, 16.5, 18.9 and 20 inches. 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 266 to 297 mm (10.5 to 11.7 in). 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, which was used on early versions of the rifle, has been replaced by the more commonly used M-LOK system.
The empty weight of a HK433 Draft STANAG 4179 compliant box magazine is approximately 160 g (5.6 oz).

## Variants

Currently are three configurations of the HK433 and two configurations of the HK437 available:
| Variant | Calibre | Length max. mm | Length min. mm | Barrel mm | Weight g |
| HK433 11" | 5.56×45mm | 843 | 577 | 280 | 3250 |
| HK433 14.5" | 5.56×45mm | 931 | 634 | 368 | 3400 |
| HK433 16.5" | 5.56×45mm | 976 | 718 | 421 | 3500 |
| HK437 Sneaker 9" | .300 Blackout | 745 | 487 | 178 | 3040 |
| HK437 Sneaker 11" | .300 Blackout | 795 | 537 | 229 | 3140 |

## Users

* Germany: Schleswig-Holstein Police
** A contract of over 200 HK437 along with accessories was procured in October 2022 for a total amount of €1.68 million.
** In 2024, the State police of Schleswig-Holstein announced the intention to replace all of their SIG Sauer MCX and Heckler & Koch MP5 models with up to 1,700 HK437 rifles by 2026.
* Germany: German Army / Kommando Spezialkräfte
** The Bundeswehr has ordered 988 HK437 rifles for the KSK.
** The HK437 will get the military identification "G39".
* Ukraine: Main Directorate of Intelligence