UNSC Ammunition

While the United Nations Space Command increasingly relied on directed energy weapons such as Particle Cannons for their main weapon types, ballistic weaponry taking the form of bullets, shells and other projectiles still accounted for a significant portion of UNSC weaponry. Particularly during the Swarm War, ballistic small arms and vehicle weapons remained popular and effective for their stark ability to penetrate The Swarm's natural exoskeleton, in contrast to energy weapons. When the Unified Coalition of Governments was formed, it maintained the same ammunition calibres as the former UNSC as this was the most logistically sensible option.

Small Arms Ammunition
Listed here are the different ammunition calibres and types of the small arms used by UNSC. Though greatly differing in calibre, these ammunition types provided a wide range in power, range, weight and accuracy, each providing the most imperative characteristics to each weapon, and each role. These ammunition types frequently were available in both the conventional chemically propelled rounds and the more powerful Electrothermal Acceleration propelled rounds. The latter method required both a capacitor and an energy source; the former needed only a standard mechanism to ignite the propellant. A weapon could accept electrothermal accelerated rounds in the same way as standard ones, the only difference being that their casing contained gas ready to be ionised by the energy source in the magazine and the capacitor in the weapon, while standard magazines lacked the energy source in the magazine and were ignited and propelled normally.

4.5x33mm
A miniaturised round designed for armour piercing qualities. While having range and accuracy properties similar to larger calibres, it maintained a much smaller weight and size, allowing for substantially reduced recoil and almost double the ammunition carrying capacity. These qualities made it excellent for use in submachine guns, such as the M8 Submachine Gun, and personal defence weapons, such as the MP8 Personal Defence Weapon System. The round was available in all small arms ammunition types. The ammunition also came in specialised types for weapons using Electrothermal Acceleration systems of propellant, in this case the ammunition consisting of just the bullet itself to save space, instead of specialised casings containing gas.

6.8x40mm
A small calibre, high velocity rifle round used in assault rifles and carbines such as the M47B Individual Combat Weapon System

7.62x51mm
M47B Individual Combat Weapon System, AR20 Individual Combat Weapon System and the M620 Light Machine Gun.

9.5x60mm
An intermediate calibre, high power rifle round used in many battle rifles. While typically producing more recoil than smaller calibres, particularly such as the 4.5x33mm, it benefited from increased stopping power and as a result, better kill efficiency. Used in battle rifles, weapons with larger calibre than assault rifles, it was long ranged and accurate, making it ideal for squad marksman duties and highly accurate mid to mid-long range combat. Weapons such as the BR62 Battle Rifle and M18 Battle Rifle benefited from this larger round. The round was available in all small arms ammunition types. For use in weapons using the Electrothermal Acceleration system of propellant, the weapon would use a specialised version of the round designed for use in such weapons. The casing did not contain an explosive propellant, but the gas needed for ionisation, allowing the bullet to be fired conventionally, with a modified cartridge, although with the advantages that were associated with Electrothermal Acceleration. This did, however, necessitate a larger casing than normal.

12.7x40mm
The 12.7x40mm round was a large calibre pistol round, used in the M21 Pistol which replaced the M6 Series of sidearms. It had good speed, accuracy, range and penetration characteristics, but was a weighty, large round, producing above average recoil. The round was available in all small arms ammunition types.

9.4x26mm
The 9.4x26mm was a standard calibre for most, more conventional pistols. While not as powerful as other pistol rounds, such as the 12.6mm, and not as small as the 4.5mm round, it was a compromise in terms of power, size and stopping power between the two, and was capable of piercing most armour. It was utilised by more conventional pistol designs such as the widely issued M31 Pistol. The round was available in all small arms ammunition types.

11.4x85mm
The 11.4x85mm calibre was mainly reserved for some lighter sniper rifles such as the M45A Compact Ranged Weapon System. It had ideal ballistic and flight qualities for a long range, powerful sniper's round. It had higher recoil than smaller rounds but was highly effective as a lethal long range round. At 4000m, and disregarding secondary damage from explosive or deforming, the round had a kinetic energy on target of 315.5 kilojuoules. This is based on a muzzle velocity of 3,500m/s.

12.5x77mm
The 12.5x77mm round was a heavy calibre round used for heavy machine guns and some sniper rifles. It had massive stopping power and penetration, but was impractical for use in any weapons but vehicle or stationary mounted ones. It had good range and armour piercing characteristics but was largely limited from small arms usage.

Ammunition Types
On top of the many calibres of weapons in the Allegiance arsenal, many different forms of ammunition were available in each calibre, substantially increasing the variability and potency of the Allegiance Armed forces. The following ammunition types were commonly available in small arms calibres:


 * RAPID/RAPID II: The RAPID round, or Reactive Armour Piercing IncenDiary, was an incendiary armour piercing round with a penetrator of tungsten, cerium and copper carbide (altogether known as TC3). This was designed to provide similar effects of a depleted uranium round, such as self-sharpening, pyrophoric and super dense, but without the side effects associated with a radiological material. The armour piercing nature of the round, coupled with the secondary incendiary effects, made the RAPID round highly effective against armoured targets, though less so against shielded ones. The RAPID II round improved the weapon's original performance and also increased its effectiveness against shields, using an condensed CVT (Chromium Vanadium Tungsten) and Austenitic Steel alloy tip coupled with a secondary TC3 penetrator. The round was coated in an advanced polymer which acquired an electric charge while in flight, aiding in shield depletion, an effect which was more useful the further the bullet travelled.


 * HEPAB: While not used as regularly as most ammunition types, HEPAB, or High Explosive Programmable Air Bursting, was a powerful munition capable of taking out multiple armoured targets. The round was fed date from the user's battle armour, which detected the target's movement, distance and such. Upon leaving the barrel the bullet was provided with data on when to burst, so that it exploded in mid air in close proximity to the target or targets, with devastating results. The bullet was composed of dozens of sub-projectiles or bars, most often condensed tungsten carbide or CVT/Austenitic Steel alloy. These were set in a powerful plasma based explosive, detonated by a timed programmed fuse. The electronic timer was programmed by inductive coupling through a device installed in the muzzle of the weapon, or through the armour itself. The timer initiated the ejection charge which released and dispersed the sub projectiles before impact with the target. The ammunition was effective against armoured infantry targets, and moderately useful at depleting shields. However, it was quite dangerous for use in close quarters, though IFF constraints in the armour usually avoided any friendly fire incidents. Nevertheless it was often used most in open or expansive battlefields.


 * HVS/AP-HE: The High Velocity Shield/Armour Piercing High Explosive was the most common form of ammunition used on the battlefield, due to its high damage and multi role nature. it was in essence the basic, standard form of ammunition used when an all round munition was needed, and was highly popular throughout the armed forces. The round consisted of a deforming ballistic cap, a dense treated CVT/Austenitic alloy penetrator, a minute particle forcefield generator to neutralise shielding, and prefragmented tungsten carbide with a high explosive in the centre. The round was able to bypass any present shielding, pierce virtually any body armour and then fragment inside the target, with devastating results.


 * HPHE: HPHE, or High Penetration High Explosive rounds, were a powerful anti armour round able to engage armoured vehicles to a limited degree, in addition to shielded and armoured targets. The tip of the shell was TC3, a laminated tungsten alloy, comprised of tungsten, cerium and copper carbide, which gave the shell extreme armour piercing properties, as well as being self sharpening and pyrophoric. The rest of the shell was prefragmented tungsten carbide, with a small hollow space in the interior. Within this space was a small forcefield generator, powered by a minute power source. Suspended within the field was a microscopic amount of antimatter, which did not come into contact with matter. Once the shell impacted on the target, the deliberately vulnerable power source would be destroyed, causing a matter-antimatter reaction and devastating any armour or targets within the blast radius. The ammunition was not very often used as it caused quite uncontrollable collateral damage, and so was unpopular for use in small arms.


 * HEPA:


 * HPSDAP:


 * HESH:

Shotgun Shell Ammunition
Designed for close and occasionally mid range combat, shotguns formed a small, though essential, part of the Allegiance arsenal. Especially used by special forces, Marines and CQB troops, they were most effective at shorter ranges, and had stopping power capable of taking down even the heaviest infantry units at optimum ranges. Their ammunition types were diverse and varied, providing a tailored response to each situation.

21mm
The 21mm shell was similar in size to the Human '8 Gauge'. It was a relatively large calibre shotgun shell, most notably used by the M105 Shotgun. It had large stopping power at close and short-medium ranges, and was popular among combat troops.

18.5mm
Smaller than the 21mm shell, the 18.5mm was analogous to the Human's '12 Gauge' shell. Although slightly less powerful than the 21mm, it was smaller which allowed greater numbers to be carried and used against the enemy. Its most widespread usage was through the D42 Close Assault Weapon System.

Ammunition Types

 * Standard Shot: Standard shells contained either 20 smaller or 10 larger spheres or advanced compressed CVT/Steel alloy. They were a perfect balance of range, shield depleting and armour piercing characteristics.


 * Sabot: Sabot shells were specially shaped, two-stage cartridges. They had an outer jacket that enabled it to travel further, outside a standard shot of 40 small spheres of molecularly compressed Chromium Vanadium Tungsten (CVT) and Austenitic Steel alloy, or alternately 15 larger ones. The shell had a long range but relatively low penetration.


 * Flechette: Flechette shells functioned in a similar manner, though replaced the shot with hundreds of molecularly compressed Chromium Vanadium Tungsten (CVT) and Austenitic Steel alloy subprojectile barbs or flechettes. These had high range and were usually deadly to armoured targets.


 * Fin-stabilised Incendiary Flechette: These were shells containing roughly 60 small fin-stabilised armour piercing flechettes. These had powerful incendiary effects to do high secondary damage after initial contact with a target.


 * Explosive Shot: Explosive shells were standard shells filled with approximately 20 smaller explosive projectiles, utilising a powerful plasma-based explosive. These had a minimum spread out of only 30cm in diameter at 30 metres after from the shooter. Penetration was low, but actual power was high, especially against shielded targets.


 * Explosive Slug: The Explosive slug was essentially a crude rifle round, using a rifled, hollow prefragmented CVT alloy slug filled with a plasma-based explosive. Some types used an incendiary component in the interior of the slug.


 * Armour Piercing Slug: The Armour Piercing shell was a simple munition focusing solely on armour perforation. It consisted of a tapered, rifled slug with a lightweight, deforming ballistic cap and an internal penetrator of CVT/Austenitic Steel alloy.


 * RAPID/RAPID II: The RAPID I/II shell was an incendiary shell for use against shielding and armour. It consisted of flechettes of molecularly compressed CVT (Chromium Vanadium Tungsten) and Austenitic Steel alloy tip, coupled with a secondary TC3 penetrator. The flechettes were coated in an advanced polymer which acquired an electric charge while in flight, aiding in shield depletion, an effect which was more useful the further the flechette travelled.


 * HEPAB: