The US Navy 7.62 NATO Garand,
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.