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Breakwater heavy naval coilgun
Mark 15 Breakwater

One of the two Breakwater turrets mounted on an Epoch-class heavy carrier.


Naval coilgun

Service history

In service:

2515 - present

Used by:



Production history


Weapon System Technologies



3,219.28 tonnes


  • Length: 104.58 metres
  • Width: 53.29 metres
  • Height: 27.82 metres

Barrel length:

79.20 metres


3,048mm ferric-tungsten kinetic kill slugs

Rate of fire:

~2 rpm

"Calling those Breakwaters 'mini-MACs' is wrong, pal. They pack more firepower than some corvettes with a spinal gun!"
―Anonymous UNSC sailor

The Breakwater heavy naval coilgun is a product line of powerful turreted coilgun batteries that is manufactured by Weapon System Technologies and used exclusively by the United Nations Space Command.


The largest weapon developed in Weapon System Technologies' Generation-8 PeaceKeeper line, the Breakwater naval coilgun is also coincidentally the largest and most powerful turreted weapon in the UNSC Navy's entire arsenal throughout the Insurrection. It is a direct response to recent relevations concerning the loyalty of the Colonial Military Administration, which revealed that Insurrectionist sympathises were rampant and threatened to destabilise human society. As a result, the Breakwater is intended as a true weapon of war: a single one of its barrels could disable any escort-grade warship in service, while breaching the armour on both cruisers and larger battlecruisers.

The Breakwater naval coilgun is built within a low, square housing, designed to reduce its size in an effort to make it harder to hit directly, as well as decrease costs associated with building them. The housing is then cut open to make room for three gigantic magnetic barrels, each of which runs for eighty metres long and reaches almost four metres in width. Despite its appearance, this configuration is anything but fragile: the barrels are capable of effortlessly resisting medium autocannon fire and light explosives thanks to being built almost completely out of steel alloys, and their moving parts use a multilayered design with interlocking components to survive punishment. The square protrusion at the base of the turret is a large but slow autoloading segment, where three individual systems are responsible for reloading the turret. If damage is sustained, the centre loading arm is capable of rearming the entire weapon, provided that there are no obstructions. Three emergency shells are always stored beneath the turret, in the event of the ammunition either running out or detonating in combat. Unlike all of WST's other naval products, the Breakwater is not self-sufficient: so much of its design is taken up by armour, a sophisticated stabilisation system, and ammunition that it only has a very basic targeting computer. As a result, orders must be fed through from the bridge or an emergency gunnery station built specifically for the coilgun.

The key component of the Breakwater is its triple-barrel design. Although concepts for a better-protected dual-barrel configuration were tested, in a shape nearly-identical to other GEN8 products, it was eventually found that such a system would be prohibitively expensive, large, and would not have the combined firepower the UNSC desired. The 16F1R5 coilguns could track up to 5o descending below level and up to 90o ascending, while the turret base tracked at 30o per second horizontally. When beginning the process of actually firing, the base of the barrels are locked into place with rigorous stabilisation equipment, and then launches its monstrous rounds at up to 17,000 metres per second. It is capable of firing sequentially, which allows for the turret to momentarily adapt to a target's movement as well as easing up on the stress inflicted on their mothership's superstructure. However, best results are achieved when firing at the same time, as studies have shown that an enemy ship has less time to avoid the full brunt of the Breakwater's salvo. In addition, the synonymous impact of all three rounds can also cause catastrophic framework or system damage on other capital ships, as well as weakening the surface armour nearby for other weapons.


Mark 15 Breakwater

The original model to be developed, the Mark 15 Breakwater was incredibly slow to load and required a monstrous amount of energy in order to charge its electromagnetic coils, which restricted it to being installed aboard battleships and heavy carriers. The large size of the round compared to the bore put considerable strain on the barrels, requiring complete replacement after only a handful of operations. As a result, all Breakwaters after 2534 were refitted with improved barrels that, as well as being harder to wear, also incorporated more efficient electromagnets to allow them to be installed on slightly-smaller vessels.

The Mark 15 Breakwater made up the main battery of the Vindication-class light battleship. In addition, both the Epoch-class heavy carrier and the Punic-class supercarrier would also feature two of these immense cannons.

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