You can spec the 7.62 in PSI, too...It's not rocket surgery...Can Am is correct.
NATO's 7.62 × 51 mm rifle cartridge, commercially known as .308 Winchester, was introduced in the 1950s as a standard firearm cartridge among NATO countries, though it has also become popular among civilians. The round is produced by many manufacturers in types that include tracers and blanks.
The military 7.62 × 51 mm is nearly identical to the commercial .308 Winchester. NATO controls specifications for the military round while SAAMI controls specifications for the civilian round. The organizations have established two differences:
the standard pressure is 50,000 psi for most military rounds, while the SAAMI maximum is 62,000 psi for the civilian round. The NATO M60 High Pressure Test round, is loaded to a pressure of 67,500 psi, so military arms should be capable of handling the pressure of civilian rounds[1]. The military chamber is specified to be 1.645 inches, compared to the civilian chamber of 1.632 inches, a difference of just 0.013 inches,[2] but a chamber at the long end of acceptable military length will put excessive stress on the thinner civilian brass, causing premature head separation. To summarize, while it is not unsafe to mix .308 and 7.62 x 51 mm ammunition, fewer problems will be encountered if the correct caliber designation is used.
The cartridge was introduced to military service in rifles and machine guns. It was used in the M14 rifle and M60 machine gun in U.S. service in the late 1950s. Fabrique Nationale's FAL became the most popular 7.62 NATO rifle in Europe and served into the early 1980s. The M14 was superseded in U.S. service as the infantry adopted a new round with the M16. However, the M14 and many other firearms that use the round remain in service. The round is used by infantry and from ground vehicles, aircraft and ships. It is used in the GE M134 Minigun as well.
http://en.wikipedia.org/wiki/7.62_x_51_mm_NATO