14.5×114mm

"High velocity, armor-piercing. They'll take the hat off an Elite at two thousand yards. And they ain't cheap."

- Jun-A266

The 14.5×114mm round is used by the United Nations Space Command's SRS99 series of sniper rifles. Multiple ammunition types are available in this cartridge.

Overview
This ammunition shares its stated dimensions with a powerful cartridge developed in the 20th century by the Soviet Union, intended as an anti-materiel and machine gun round. The UNSC employ it in their own anti-materiel sniper rifles, which are highly effective when used to engage and destroy enemy equipment, vehicles and infantry, though the latter is not their intended primary function. It has been noted, however, that in an anti-personnel role, weapons firing this cartridge possess admirable performance against advanced Covenant energy shield technology. While there exists a variety of ammunition types available in this cartridge, they tend to be highly damaging, precise and effective at long range.

APFSDS
The 14.5×114mm APFSDS (armor-piercing, fin-stabilized, discarding sabot) round is the most commonly employed ammunition type for use with the SRS99 series. The damaging capability of the 14.5×114mm round is impressive; according to a UNSC serviceman, at 600 yards the round will go through about 13 feet of flesh and bone when fired from an SRS99D-S2 AM sniper rifle. This makes it easily capable of over-penetrating armored soldiers and whatever was behind them, making caution paramount when employing this ammo. The round is also highly potent at inflicting damage against light vehicles. Ammunition of this type which was utilized in 2557 aboard the UNSC Infinity with the SRS99-S5 AM sniper rifle bore the alphanumeric designation "M232".

Inferring from the designation "armor-piercing, fin-stabilized, discarding sabot", and certain visual depictions, the APFSDS round functions in a similar way to a form of ammunition traditionally used with the cannons of main battle tanks. The bullet is of subcaliber dimensions (meaning that it is too narrow to grip the bore of the barrel), and possesses a long, thin, dart-like shape. Such projectiles can be referred to as a "penetrator" or a "flechette". To allow the projectile to function, it is contained while travelling down the barrel in a structural device called a "sabot", which keeps it centered in the bore and is then discarded in flight. The projectile is stabilized in the air by a set of fins, increasing accuracy. Such ammunition has the benefit of minimizing air resistance, allowing it to maintain exceptionally high velocities over long distances which greatly increase effective range, accuracy and penetrative power. They are constructed from dense, hard materials to maximize inertia and resilience, further improving damaging potential.

HVAP
The 14.5×114mm HVAP (high-velocity, armor-piercing) round is an alternate ammunition type to the standard APFSDS which was used with SRS99-AM sniper rifles during the Battle of Reach. According to Spartan Jun-A266, the round is sufficient to "take the hat off an elite at 2,000 yards." He also implied that they were highly expensive.

Judging from their designation, these rounds work in the same way as a real-world anti-armor ammunition type typically used in the weapons of 20th century combat vehicles. Also referred to as APCR (armor-piercing composite rigid), but known as HVAP to the military of the United States, the basic design is a core of dense, hard material encapsulated in a conventional full-bore projectile of comparatively lesser durability and density. On impact, the energy of the round is concentrated into the dense core, working to drive it through armor plating. While the function of this round in large-caliber ammunition has largely been overruled by APDS (armor-piercing, discarding-sabot) and APFSDS, many small arms ammunition types designed to be capable of damaging lightly armored vehicles or penetrating body armor make use of the same basic design.

HEAP
The 14.5×114mm HEAP (High-Explosive, Armor Piercing) round is used by Linda-058 in her personal modified rifle Nornfang. These rounds explode violently on impact, dealing a great deal of damage to the target.

Trivia

 * The Steyr ACR is a real-world prototype weapon that was designed to fire a 5.56mm flechette, similar to the 14.5mm APFSDS used in Halo. However, this weapon is a select fire assault rifle, rather than a sniper rifle.
 * The 14.5×114mm is actually a Russian heavy machine gun round that was developed for use in anti-tank rifles like the PTRD and PTRS in World War II, later used in Anti-Aircraft and Vehicle-Mounted roles with the KPV; it remains in use to this day.

List of appearances

 * Halo: The Fall of Reach
 * Halo: Combat Evolved
 * Halo: The Flood
 * Halo: First Strike
 * Halo 2
 * Halo Graphic Novel
 * Armor Testing
 * Halo: Ghosts of Onyx
 * Halo 3
 * Halo: Contact Harvest
 * Halo: The Cole Protocol
 * Halo Wars
 * Halo 3: ODST


 * Halo Legends
 * Homecoming
 * Prototype
 * The Babysitter
 * Halo: Blood Line
 * Halo: Fall of Reach
 * Boot Camp
 * Invasion
 * Halo: Glasslands
 * Halo: Combat Evolved Anniversary
 * Halo 4
 * Spartan Ops
 * Halo: Spartan Assault
 * Halo 2: Anniversary
 * Hunt the Truth
 * Halo 5: Guardians
 * Halo: Fractures
 * Breaking Strain
 * Halo: Envoy