During the late 1950’s the US Military adopted the M14 rifle to replace the older M1 Garand. Chambered in 7.62 NATO (7.62X51), the standard cartridge of most NATO and western countries, the M14 was a semi/fully automatic design based on the older Garand. During it’s production the Army and Marines were given priority when it came to its issuance, the Navy was considered to have low priority when it came to small arms. As a result the Navy often suffered from shortages of rifles.
To ensure that they had enough rifles, the Navy sought to modify its older stocks of World War II and Korean War vintage M1 Garand’s. To share common caliber with the M14, the Navy enacted a program to modify the old M1 Garand from .30-06 to 7.62 NATO. To save money they purchased a special chamber adapter which could supposedly be installed upon delivery. The user simply had to insert the adapter into the chamber and test fire it three times so that the adapter would pressure seal into the chamber.
While the new adapter system saved the US Navy money, it was also difficult to install and dangerous to use. Many of the adapters were too small for the M1 Garand’s chamber and could not be safely installed. As a result the Navy the turned to the traditional method of caliber modification; reboring and rechambering the the barrels of the M1 Garand.
Companies such a Harrington and Richardson, American Machine and Foundry, and the Springfield Armory were contracted to produce the conversions. Altogether around 62,000 M1 Garands were converted to 7.62 NATO by the Navy. They remained in use throughout the 1960’s, and even were used as training rifles up to the mid 1970’s. They were eventually replaced with the M14 and the even newer M16 assault rifle.
Designed as an improved version of the infamous MG-42 machine gun, Rheinmetall of Germany produced a single prototype of the MG-60, while Swiss armorer SIG created the other prototype. The MG-60 was 43.8 inches long and considerably lighter than the MG-42, at only 8.6kg. It had a firing rate of around 800-1000 rounds per minute. Both the Rheinmetall and SIG prototypes were trialed at Wehrtechnische Dienstelle-91 at Meppen, but neither prototypes were successful. The Rheinmetall prototype can be seen at the Wehrtechnische Studiensammlung museum in Koblenz, Germany. (Photo is taken from a book, so the barrel isn’t actually bent, that’s just the page folding!)
Following the revision of the OICWBlock 1 / XM8 program, the Heckler & Koch company decided to enter the US military and law enforcement markets with the alternative design, which, in fact, looks quite promising. Based on the experience, gained during successful upgrade program of the British SA80 / L85A1 program, HK decided to cure the existing M16 rifles and M4 carbines from most of their problems, inherent to this 40-years old design.The key improvements, made by HK, are their patented short-stroke gas piston system, borrowed from HK G36 rifle. This system replaced the direct gas system of standard M16 rifle, so no powder residue will remain in the receiver even after long shooting sessions. The “new"gas system also is self-regulating and will work reliably with any barrel length. Other improvements include new buffer assembly, improved bolt, and a cold hammer forged barrel, as well as free-floating hand guard with integral Picatinny-type rails. Originally developed as a "drop-in” upper receiver assembly for any standard M16/M4 type lower receiver, HK416 is also available as a complete weapon, with HK-made lower receivers. Current (late 2005) models include carbines with 10.5" and14.5" barrels, and 16.5" barrelled carbine and 20" barrelled rifle will be added later. 7
Another interesting development, which is apparently based on the up scaled HK416 design, is the HK417 - the 7.62x51 NATO rifle that combines AR-15/M16 type ergonomics, layout and handling with improved reliability of HK-made and designed gas piston system. This rifle probably will use HK G3-type magazines. If the rumours about HK417 are true, the 5.56mm HK416 / 7.62mm HK417 combination will be a direct rival to the newest FN SCAR system.
HK416 is a gas operated, selective fired weapon of modular design. It uses short-stroke gas piston that operates the 7-lug rotating bolt. Receiver is made from high grade aluminium alloy. Combination-type safety / fire selector allows for single shots and full automatic mode. Hk416 retains all M16-style controls, including last round bolt hold-open device, rear-based charging handle and magazine release button on the right side of the magazine well. HK416 is fitted with four Picatinny rails as standard, and may accept any type of sighting devices on STANAG-1913 compliant mounts. It also can accept modified HK AG36/AG-C 40mm grenade launcher, which is clamped directly to bottom rail. Butt-stock is of typical M4 design, multi-position telescoped.