After using the HK417 as a stopgap designated marksman rifle under the G27 designation, the civilian MR308 was used to develop the G28, a designated marksman rifle for the German Bundeswehr (Federal Army) deployment to the war in Afghanistan. The semi-automatic G28 is chambered for 7.62×51mm NATO and has a factory warrantied accuracy of 45 mm dispersion at 100 meters (0.45 mil or 1.5 moa) when fired with 10 rounds using OTM/HPBT/Sierra Match King ammunition. The G28 features STANAG 4694 NATO accessary rails that are backwards-compatible with the STANAG 2324/MIL-STD-1913 picatinny rails. The upper receiver is made from steel instead of HK's aluminum alloy. Approximately 75% of the parts are interchangeable with the HK417. There are two different versions of the G28: G28 E2 (Standard) with a Schmidt & Bender 3–20×50 PM II (modified to Bundeswehr requirements) and the G28 E3 (Patrol) with Schmidt & Bender 1–8×24 PM II. By October 2017, Heckler & Koch had renamed the G28 as the HK241, though G28 remains its Bundeswehr designation.
The Heckler & Koch HK433 assault rifle is a gas operated, selective fire weapon. It features short stroke gas piston, located above the barrel, with manual gas regulator. Barrels are easily removable after partial disassembly, and are offered in several lengths, ranging from 28 to 50 cm (11 to 20 inches). Barrel locking is achieved by a G36-style rotating bolt that locks directly into the barrel extension, and the bolt carrier group is also based on HK G36, with several improvements in detail.
Upper receiver is made from aluminum alloy; lower receiver, which consists of a trigger housing, magazine housing and a pistol grip, is made from polymer. The rifle is equipped with ambidextrous 3-position safety / selector lever which permits for single shots and full automatic fire.
Lower receiver is available in two alternate versions, with M16-style controls (side-mounted ambidextrous magazine release buttons) or G36-style controls (paddle-type magazine release at the bottom).
An ambidextrous bolt hold-open lever is present in either configuration. The folding charging handle is non reciprocating, but can be locked in to be used as a bolt closure assist, and can be mounted on either side of the gun, depending on users’ choice. The weapon is fed using STANAG-compatible (M16 type) magazines.
Adjustable shoulder stock is made from polymer, and folds to the right. Sighting equipment can be installed onto an integrated Picatinny rail that runs the entire length of the monolithic upper receiver.
The slim forend has KeyMod slots on its sides and a bottom rail, which can host 40m grenade launcher or a variety of tactical accessories like lights, lasers and foregrips. The HK433 rifle features integral, battery-free electronic shot counter than can transmit info (useful for maintenance) using RFID technology.
An illustrated view of the components that make up the HK 433