7.62x51mm



7.62x51mm NATO is a round used by the UNSC in their MA5 Series of assault rifles. It was originally developed by the NATO organization in the 20th Century. It is used due to its reliability and heavy power.

As it is used with the MA5 rifles, which are one of the most common armaments in the Marine Corps, it is probably the most commonly fired and used round in the UNSC ground forces. It can be regularly found in packs littered around battlefields.

The round is effective against infantry, especially against unarmored or unshielded opponents. Energy shields drastically reduce the effectiveness of this round, as it does not have enough kinetic energy to significantly drain the shields. The round is also largely ineffective against vehicles, as it is not significantly armor-piercing. Massed fire from a squad of Marines, however, is enough to drain shields and destroy or disable most vehicles short of tanks due to the sheer number of rounds fired. Thus, this is primarily an infantryman's round for use against other infantry.

History
The 7.62x51mm NATO was originally developed by NATO, an organization of national governments, in the middle of the 20th century. It was developed to be reliable when used in fully automatic weapons, to have a large punch, and to standardize round size between governments. It replaced a variety of smaller ammunition and largely achieved the goals of development. It is a full-power rifle round in the 20th century, and is fairly common in machine guns and sniper rifles, but not in lightweight assault rifles like the MA5 series because of intense recoil. Its ineffectiveness in individual infantry weapons led to the adoption of the adoption of the 5.56x45mm NATO round, due to better controllability and the ability to fit it into small, lightweight assault weapons. It is not known why the 5.56x45mm NATO round disappears in the Halo universe, but it could be possible that weapons technology advanced so much as to fit enough recoil control systems on a firearm to allow this powerful round be used as an infantry rifle round (the same could apply to the M6 series).

Trivia

 * This round was developed by the modern day, real life organization NATO, which stands for North Atlantic Treaty Organization.
 * In Halo: Combat Evolved, this round is labeled "M118 7.62x51mm FMJ-AP." [[Image:7.62.jpg|right|thumb|The labeling on a pack of 7.62x51mm ammunition.]]This means that the rounds are armor-piercing and have a solid outer coat of metal.
 * In reality, this round produces too much chamber pressure and recoil to be used in an automatic small arm. Also, the MA5B and MA5C appear to have no muzzle brakes, but the recoil appears to be somewhat low.
 * It takes 16 rounds to kill a fully-shielded player in Halo 3 multiplayer.