Heckler & Koch HK417

The Heckler & Koch HK417 is a battle rifle designed and manufactured in Germany by Heckler & Koch. It is a gas-operated, selective fire rifle with a rotating bolt and is essentially an enlarged HK416 assault rifle. Chambered for the full power 7.62x51mm NATO round, instead of a less powerful intermediate cartridge, the HK417 is intended for use as a designated marksman rifle, and in other roles where the greater penetrative power and range of the 7.62x51mm NATO round are required. It has been adopted for service by a number of armed forces, special forces, and police organizations.

Design Details
The HK417 is similar in internal design to the HK416, but the receiver and working parts are enlarged to suit the larger 7.62x51mm NATO round. The bolt is a 7-lug rotating type, which sits in a bolt carrier and operates in a forged alloy receiver resembling those of the Stoner-designed AR-10, AR-15 and M16 series weapons. Like the HK416, the HK417 is a gas-operated, with a short-stroke piston design similar to those found G36. The short-stroke piston is more reliable than the original direct impingement operation of the AR-10 and AR-15 designs because, unlike these weapons, it does not vent propellant gases directly into the receiver, which deposits carbon fouling onto the bolt mechanism as well as heating it up; such carbon fouling leads to more malfunctions.

The early prototype HK417 used 20-round magazines from the H&K G3 rifle family, which did not feature a bolt hold-open device. Later prototypes, however, switched to a polymer magazine with bolt hold-open. The magazine resembles an enlarged version of the G36 series transparent magazine, except without the pins for holding more than one magazine together. In addition, a 50-round, low profile drum magazine developed by HK for the HK21E machine gun can be fitted to the HK417 for use in support and sustained fire applications.

Role
Purchasers of the HK417 have typically intended it to complement lighter assault rifles chambered for less powerful intermediate cartridges (often 5.56x45mm NATO), for the designated marksman's role. The HK417's greater accuracy, effective range, and penetration offset its greater expense, its lower rate of fire, and its smaller ammunition capacity both in magazine and carriage.

The HK417 is available only to such government agencies as law enforcement, security forces, and the military.

Variants
The HK417 is currently available with three different barrel lengths (all in 7.62x51mm NATO):
 * HK417 12" 'Assaulter' Model – 12" standard barrel
 * HK417 16" 'Recce' or 'Recon' Model – 16" standard and accurized barrels
 * HK417 20" 'Sniper' Model – 20" accurized barrel

Accurized barrels provide 1 MOA accuracy (with match grade ammunition). A barrel can be changed in under two minutes with simple tools. All HK417 barrels are cold hammer forged and chrome-lined and use a conventional lands and grooves bore profile with a 279.4 mm (1 in 11 in) twist rate. They are designed to function reliably with bullet weights ranging from less than 9.3 to 11.34 g (147 to 175 grains) and are threaded for flash hider, muzzle compensator, and sound suppressor attachment.

Related developments
The HK416 is a smaller version of the HK417 chambered for the less powerful 5.56x45mm NATO round. The HK416 is designed for military and law enforcement use. At the 2009 SHOT Show, two firearms were introduced to the American civilian market renamed respectively MR556 and MR762. These are civilian sport rifles versions.

G28
The civilian MR308 was used to develop the G28, a designated marksman rifle for the German Bundeswehr (Federal Army) deployment to the Afghanistan war. The semi-automatic G28 designated marksman rifle is chambered for 7.62x51mm NATO and has a factory warranted accuracy of 45 mm dispersion at 100 meters (1.5 MOA) when fired with 10 rounds using OTM/HPBT/Sierra Match King ammunition. The G28 features STANAG 4694 NATO Accessory Rails that are backwards-compatible with the STANAG 2324 or MIL-STD 1913 Picatinny rails. The upper receiver is made from steel instead of HK's aluminium alloy. Approximately 75% of the parts are interchangeable with the HK417.