Rampart point defense gun

The Rampart point defence gun is a line of related close-in weapon systems that are manufactured by Emerson Tactical Systems for the UNSC Navy.

Design
Although the Rampart family encompasses weapon systems of all different styles and construction, they all feature the same basic qualities. Their basic construction consists of a quad-linked barrel setup, sitting on the exterior sides of a central core that contains the motors, targeting computer, and ammunition loading lifts for the cannons. Their primary optics are built into either the forward face or a protrusion on the top of the core, and simultaneously scan through various radio, infrared, light, and ultraviolet spectrums to acquire targets. No Rampart turret has a local ammunition dump built within their exposed structure, with the rounds being selected and stored below the surface of the armour they are installed upon. Their skeletal configuration means that, although they can be damaged with sustained fire from space fighters, they are easy to repair and can eject specific major components if they are inoperable or being replaced during maintenance. No Rampart turret has any other secondary systems, such as missiles or countermeasure launchers to confuse attacks. In general, Rampart turrets are simple, easy to maintain, and can maintain a staggering rate of fire, at least when compared to their rivals.

M800 Rampart
No longer manufactured, but remaining in service due to the vast quantities of weapon systems available, the M800 Rampart is a 40mm gun battery that innovated the configuration that would be used for all later turrets of the family. It is universally outclassed in all areas by its successors, with each barrel only being able to suppress attackers with ~300 rounds per minute (RPM). The UNSC has reclaimed vast numbers of M800s from extensive refitting programs during the Insurrection and the early Human-Covenant War, and they found new life as planetary anti-air emplacements on contested colonies.

M870 Rampart
The M870 model of Rampart is easily the most widely adopted model of the design family, well-regarded due to its traits being analogous to a 'middle child' of the Rampart line. Smaller and weaker than later revisions, it is still more dangerous than earlier attempts, and its abundance has seen it being used on everything from corvettes and freighters all the way up to supercarriers.

The M870 Rampart is designed as a squat turret, with two linked batteries each consisting of twin 50mm barrels sitting on either side of the rotating core. This configuration ensures that both portions are each capable of traversing a full 180o vertically. Secondary sensor optics in each rotating battery, as well as information fed from the mothership's main computer, means that they can still effectively engage missiles and fighters from behind if necessary. The M870's 50mm rounds, while packing a smaller punch than other point defence guns, are fired at extraordinarily high velocities, and so they can easily cover a range of 20 kilometres around them. They can also autonomously select from a wide range of ammunition types, from flak to ultradense rounds to magnetised shells for defeating plasma torpedoes. Each barrel can fire up to 360 rounds per minute, for a total of 1,440RPM. Although they cannot split their fire, as only a single motor controls both the batteries, the skeletal, segmented design means that repairs are a straightforward matter. If a component fails, it can be easily disconnected and replaced at a moment's notice.

M870B Rampart
A later hybrid model, the M870B actually shares very little with the predecessor for which it takes its name, and instead most of its architecture is actually taken from the M910 turret. Although it marries high-velocity, rather small slugs with the sequential revisions that have resulted in a tougher, more versatile weapon system, it inherits the weakness of being limited to a 110o vertical elevation limit for its lower barrels. Its main benefit is its cost-effective price tag.

M910 Rampart
First emerging during the Insurrection, when Titanium-A1-clad space fighters began to circulate around rogue forces, the M910 Rampart is much more significant jump in power and capability over its predecessors. It is built on a slim, boxy chassis, with six-metre-long barrels that are designed to fire off 105mm slugs at acceptable speed and power. These are typically kinetic penetrator slugs made from tungsten, with a wide variety of other shells - magnetised, fragmentation, and high-velocity guided rounds all typically being available as standard - being easily loaded by a revamped targeting network. Each gun is only able to maintain a steady rate of ~180RPM, for a total of 720RPM across the entire mount. Slightly faster cycling is possible if the M910 selects subcalibre 90mm rounds, as only two of the three electromagnet coils in each cannon are needed to accelerate them to high speeds. Besides the weaponry, many minor upgrades have been added into the new design. The turret's armour is considerably more durable, with a maximum thickness of 70mm, and the cheaper ferric-ceramic plating is replaced with a titanium hull. It can also turn quicker, track opponents through more chaotic environments, and is designed with a targeting system that increases in performance with the more point defence guns it controls. Unfortunately, there are many weaknesses in the M910 model, and while widespread many shipwrights continue to retain the previous M870. Each turret is only capable of firing along its forward face, with a maximum elevation of 110o because the uppermost guns block the passage of the lower pair. This could potentially leave a small gap that can be exploited by missiles and fighters to seriously harm the vessel or installation they are mounted on, leading to unnecessary loss of life.