AIR-481 carbine

"Gone are the days where I needed to carry a full damned armoury into the field. My new AIR carbine can do everything that I would need three other rifles for - with nowhere near the bulk."

- Anonymous

The Advanced Interchangeable Rifle-481 (AIR-481) is a compact firearm in service with the. It is manufactured by as a single platform that can be reconfigured into a wide variety of weapon types in the middle of the battlefield, offsetting the size and weight issues associated with carrying a number of large, heavy firearms at once. It is currently limited to operatives, as its price and need for specialised training has prevented it from seeing more widespread adoption.

Design Details
Because it is intended to function as the base for so many different weapon systems, the base core of the weapon needed to be over-engineered for all possible circumstances. The demands of each configuration meant that it needed to remain small and light, but robust enough to retain the space for a large integrated battery and recoil-dampening system. The unique challenges involved meant that it has suffered a history of unreliability during its development cycle, a reputation that it has not quite been able to shake off more than two decades later.

Retaining only a very-short barrel, the basic core of the AIR is of an ambidextrous design, with a downward ejection port, and a magazine slot on either side of the weapon. This distinguishes it from nearly every other weapon currently employed by the UNSC, which all tend to be of bullpup organisation, which gives it a short barrel length for its size no matter the configuration. It visually resembles a larger version of an unloaded, with hooks and docks lining the missing barrel segment. Because the various specialist components are too large and heavy to be accommodated by a single tactical rail, twin rails locks are installed to hold them in place. The rearmost section of the core does not incorporate a retractable stock, but instead is devoted entirely to a large recoil-control system designed specifically for the AIR. As a base component, it is developed to operate independently of any mission-specific parts, but if needed it is fully capable of interlinking with supplemental dampening chambers to augment it. Iron sights are natively provided, and slide into spring-loaded hatches when a scope is added. To fit non-standard scopes and foregrips, two tactical rails, one of the top and the other at the front, are included. A cover on the back of the AIR can be removed to allow for external stocks.

The hardened electronic suite on the AIR-481 is one-of-a-kind, with a high-capacity 48V battery slipped into the stock providing the power. It is -compatible, as is standard among UNSC firearms, automatically uploading ammunition capacity, safety diagnostic checks, and reticule pairing to the user's. The suite is built in the centre of the weapon, below where the three-digit digital counters are located. Although they helpfully change colours to reflect the state of the magazines, changing from blue, yellow, and red, many Marines have disliked the placement as it is less clearly visible compared to the likes of the. The suite controls many aspects of the AIR's operation, from recoil-control to firing. The extensive use of the battery means that, although it has a redundant system to allow it to still function in the event of no power, has been a primary contributor to complaints regarding reliability in the field.

Carbine
In its default, factory-standard model, the AIR-481 is a short gas-operated carbine that aims to occupy the gap between the UNSC's full-sized carbines and submachine guns, the goal being to combine the strengths of both types. It is lighter, substantially easier to manage when firing, and have a proportionally-larger magazine than the, while it is chambered with larger rounds and a longer barrel than the. By using this middle-child philosophy, Acheron hopes it would appeal to a wider pool of vehicle operators and aircraft pilots, as well as personnel conducting Military Operations in Urban Terrain (MOUT).

The carbine meets the UNSC's standard of 900 rounds per minute, with a selector switch on each side that can switch it from safety, semi-automatic, and fully-automatic fire. Earlier variants had tested a three-round burst setting, although it was removed after it was discovered that early operators did not find any use for it, as the weapon is surprisingly easy to keep level. It is noted as the most rugged configuration of the weapon, withstanding mud, water, ice, and the occasional bumps in the field, although it is still more temperamental than other firearms already in service.

The carbine configuration uses the now-outdated M142 5.56x45mm round, a small assault rifle cartridge that was popular during the UNSC's formative centuries. A smaller, lighter companion to the earlier, both rounds share the hardened construction that helps them beat heavy armour. The M142 has been discarded by the military because it cannot match the range, accuracy, and destructive capacity of a 7.62mm. This is because it is too light to overcome air resistance, which makes it more prone to submitting to changes in its trajectory thanks to wind. However, it is a much more effective round within a 100 metre radius, thanks to its initially-higher muzzle velocity. They come in magazines of thirty on average, although larger boxes which are filled with sixty are also available. Specialised ammunition, such as, hollow points, and incendiary, are available but require approval from the UNSC Ordnance Commission.