7.62x51mm

An overview of the M118 round.

The M118 Full Metal Jacket Armor-Piercing^[1] is a 7.62×51mm rifle cartridge commonly used in the United Nations Space Command's MA5 series of assault rifles.

Overview

The M118 FMJ-AP round is the standard-issue 7.62x51mm ammunition utilised by the the UNSC Armed Forces, with other options including 7.62x51mm shredder rounds. Its armor-piercing properties stem from its specially hardened construction.^[2] It can be regularly found in 120-round packs wherever UNSC forces utilising MA5 series rifles are engaged.

The following weapons in UNSC usage are chambered for 7.62x51mm ammunition and typically make use of M118 FMJ-AP rounds;

MA5 series assault rifles
M392 and M395 Designated Marksman Rifles
M739 Light Machine Gun
M247 General Purpose Machine Gun and M247T Medium Machine Gun

Performance

Weapons chambered for 7.62x51mm ammunition such as the MA5B assault rifle are considered to be powerful by UNSC soldiers.^[2] UNSC infantry combat armor is capable of preventing lethal penetration at close range from a limited burst,^[3] though infantry and even light vehicles or aircraft such as un-shielded Covenant Banshees are easily susceptible to fatal damage under sustained, accurate fire.^[4] Energy shields drastically reduce the ammunition's stopping power, as a great deal of concentrated fire from multiple weapons - or an extended period of continuous automatic fire from a single weapon - is needed to overwhelm them utilising this round.^[2]

Real world background

There is more information available on this subject at 7.62×51mm NATO on the English Wikipedia.

The 7.62×51mm NATO round was originally developed by NATO, a military alliance between 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 service rifle calibers between governments, in order to improve logistics. It replaced a variety of smaller ammunition and largely achieved the goals of development.

Gallery

An M118 ammo pack in Halo: Combat Evolved.
Packet of the M118.
An M118 bullet pulled out of Zhao Heng Lopez's shoulder in The Mona Lisa.
Closeup of an M118 FMJ-AP cartridge in an MA5D's magazine in Halo 4.
NATO 7 62x51.jpg

Real-life 7.62×51mm NATO rounds, with a ruler and AA battery for scale.