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KSM1 Jabber
Production information

Kovac and Sons Motor Company

Technical specifications

21.65 feet (6.6 meters)


10.83 feet (3.3 meters)


9.84 feet (3 meters)

  • 50 tons (45,359 kg) (KSM1)
  • 52 tons (47,174 kg) (KSM1A2)
Maximum acceleration
  • 5.7 Seconds (0 to 30 mph) (KSM1)
  • 5.8 Seconds (0 to 30 mph) (KSM1A2)

Kovac and Sons Morvarc'h Hydrogen Fuel Cell/Electric Motor System, 2,012 hp (1,500 kW)


Equipped on select UNSC M431A2 MBT models

  • Titanium-A Backed Composite Armor
  • Refractive Coating
Sensor Systems
  • Active and Passive Radar Systems
  • Commander's Independent Multiwavelength Viewer
  • Gunner's Multiwavelength Manual Sight
  • Driver's Primary Visualization System
  • Several manual viewports
Targeting systems

SGD6672 Fire Control Computer

  • 2 x SGD900 Smoke Grenade Launchers (6 Barrelled)
  • Inert gas fire suppression systems
  • SGD Active Protection System



  • 1 x .50 caliber (12.7 mm) SSA223 Heavy Machine Gun (Commander's Remote Weapon Station)
  • 1 x 7.62 mm (.308 in) SSA107 General Purpose Machine Gun (Coaxial)

3 (Commander, Gunner, Driver)

Year introduced
  • 2537 (KSM1)
  • 2555 (KSM1A2)

Universal Armored Warfare


The KSM1 Jabber (officially KSM1 MBT within the Sironan Militia and M471 MBT across the UNSC) is a main battle tank primarily utilized by the Sironan Militia, though it has also seen limited service within the UNSC Marine Corps and UNSC Army and a handful have fallen into the hands of various Insurrectionist cells. Smaller and less powerfully armed but faster and with theoretically higher levels of protection than the M808 line of Scorpion tanks, the KSM1 MBT line was developed by Kovac and Sons Motor Company to specifically face the perceived threats presented by the Covenant while remaining significantly cheaper than its counterpart to fit within the budgetary needs of the Militia.

These combined needs are seen by looking at the companies involved with the development of the vehicle. To cut costs, all were smaller, local Sironan companies rather than the larger corporations associated with most UNSC vehicles, such as Misriah Armory or Chalybs Defense Solutions. Additionally, the tank and its gun were both smaller and lighter than the Scorpion and its M512 90 mm Cannon respectively, affording the similar engine power to lead to a significantly more efficient vehicle. Additionally, while potential damage on rounds that managed to penetrate was lessened due to the smaller 75 mm caliber of the gun (further exacerbated by the common usage of self-sharpening sabot rounds), the usage of Electrothermal-chemical propellants allowed for significantly higher and more reliable muzzle velocities, leading to a higher penetration power on the typical rounds fired by the KSM1 compared to the Scorpion. However, this did also lead to a sacrifice when it came to high-explosive rounds and anti-tank missiles fired by the vehicle due to the smaller overall bore size.

However, the vehicle performed well enough during the Human-Covenant War that the Sironan Militia took advantage of its increased budget to order an upgrade to the tank in the form of the KSM1A2 (M471A2) Jabber to gradually replace the older model starting in 2555, with the A2 featuring slightly thicker armor overall, an additional coaxial 25 mm M68 Gauss Cannon, and a larger turret. Some select tanks within this later line of Jabbers have also seen the trial integration of shielding technology, though all of these have been within the hands of the UNSC rather than the Sironan Militia.

Developmental History

The first murmurings that the Sironan Militia could make use of its own main battle tank, rather than relying on UNICOM Scorpions, arose in the early 2510s, following the First Battle of Sirona. While the UNSC forces on the ground had managed to quickly defeat the Insurrectionists that had attacked the Sironan military HQ, the few Insurrectionist forces that had diverted to attack civilian populations faced far less effective resistance from members of the militia, particularly those that made use of their own captured and makeshift armored vehicles. While the UNSC forces eventually handled these lingering forces following the conclusion of the main conflict, many members and leaders of the militia remained frustrated at their lack of effective means to handle heavily armed and armored hostile forces without this support.

However, despite these frustrations, the increased deployment of UNSC forces to Sirona, growing distrust among UEG officials of colonial paramilitary groups, and a general lack of funding saw the variety of proposals for a Sironan Militia MBT (largely based off of Scorpion designs) fail to get past even the design phase, with those that did manage to result in prototypes failing to meet the requirements of the militia or warrant serious consideration due to concerns about production capabilities. Even when the Covenant attacked in the mid-2520s, progress remained slow—even stagnant—as the official UEG stance withheld information about the true extent of the Covenant threat from colonial governments and populations. However, as the war progressed, UEG opposition to colonial paramilitary groups, particularly those on Inner Colonies, grew inversely to the relative decline in Insurrectionist activity. Additionally, under the increased demand for medical supplies and the introduction of Colonial Governor Anna Masson's economic reforms, Sirona's economy skyrocketed and saw the expansion of many of its smaller companies.

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KSMC's original concept design for what would later become the Jabber.

In early-2532, one of these smaller companies, Kovac and Sons Motor Company (KSMC), found itself undergoing rapid explorations into other aspects of the market, particularly defense contracting and military vehicles. Knowing that they couldn't hope to compete with the larger, inter-colonial firms, the new combat vehicles division of the company saw a way into the market by—rather than waiting for military and paramilitary groups to come to them—first approaching the Sironan Militia with a proposal to fulfill the need for an MBT cheaply and quickly. With the militia itself getting more funding, KSMC's automobile factories ready to be converted into high-end production lines for the new tank, and the preliminary concept art—based once again on the Scorpion but incorporating weapons and technology from other smaller defense contractors on Sirona—showing promise that others previously had lacked, the Sironan Militia quickly signed a contract with KSMC to begin the further development of the vehicle as soon as possible, agreeing on terms and a development budget within less than a week of the first meeting.

The development of the Jabber began later that year in June of 2532 once all of the details of the agreement had been settled. Over the next nine years, the design of the hull and turret had been produced by KSMC with the processed slowed by the company's newcomer status to the creation of a tank, the project's start-from-scratch nature, and the introduction of new information about the Covenant as the war went on leading to changes in design philosophy several times throughout the process. Additionally, the development of methods to produce titanium-carbide armor plates and scale the standard KSMC electric motor arrangement to the scale required for a vessel the size of the Jabber ate into the development budget leading to reductions in spending on manpower in other areas of the design.

Despite these setbacks and the slow-going nature of the project, the vehicle was ready for prototyping in March 2541 and the first prototype models, the KSMX-1 Jabber, came off the production line—fitted with 7500mm (100 calibers) main cannons from Sironan General Defense—by that November. The Sironan Militia ran combat environment tests using these prototypes over the next few months until, in April 2542, they returned to KSMC with news of several issues with the tank. The most noticeable of these issues was that the main cannon's length proved too unwieldy for the size of the Jabber and, more specifically, its turret, leading to issues with aiming and firing accurately. Additionally, the suspension and electric motor systems both proved underpowered for a tank of the Jabber's size and the battery-based electric storage system proved unable to provide a sufficient stock of electricity for the tank to undergo any extended deployments.

As such, KSMC returned to the design phase to fix the issues. Contacting Sironan General Defense, they had the gun reduced in length to 88 calibers. At the same time, they worked in house—armed with a budget extension from the Sironan Militia—to strengthen the suspension, increase the power of the electric motors, and completely replace the battery-based electric storage system with a new hydrogen fuel cell system. By October 2542, the changes had been implemented and by January 2543 the KSMX-2 Jabber prototypes had been delivered to the Sironan Militia for testing. After another several-month testing run, the Sironan Militia approved the tank for standard production and—with only a few changes for comfort and identification on the battlefield—the first run of 20 Jabbers were delivered to the Sironan Militia by July 2543, with the original 8 KSMX-2 Jabbers coming back after being converted to KSM1s by August.

Operational History

Now with 28 Jabbers at their disposal, the Sironan Militia soon after faced another issue, this one logistical. With the new system for powering the vessel in place, there had only been time to outfit one Sironan Militia base with the proper equipment to refuel and charge the tanks. However, this base also lacked the space to hold more than two-dozen armored vehicles, instead limited to only a set of seven as this was the original number of vehicles it was intended to house before the changes in the production run. As such, it was eventually decided to distribute the Jabbers evenly across the militia bases, with seven vehicles going to each of the four main militia bases across the planet. Production of charging and refueling stations thus became a priority in the militia bases outside of Maponos, Bodua, and Esos while the Grannus base staff began training programs with the new vehicles among their tankers.

With these priorities set and the Jabbers arriving at their respective bases by later in July 2543, the Sironan Militia worked quickly to address the logistics issues surrounding the housing of the vehicles. By September of that same year, all four bases had been fully upgraded to be able to refuel their tanks and training on the vehicles began in full across the entire Militia. By the middle of November, the tankers at the Grannus installation had been fully trained in the operation of the new vehicles and they were shortly afterwards—by the middle of December—joined by their fellow militiamen across the other three installations. In fact, on December 20, 2543, the militia even held a tank crew competition across the four militia bases.

During this competition, the UNSC proper had its first exposure to the Jabber. Impressed by the performance of the vehicles that he saw on display, a Marine armored division Colonel who had just arrived at the planet from fighting on the Atlas moons informed his superiors of what he saw. Eventually, this information worked its way up the chain of command and, by February 2544, an arrangement had been made between the UNSC Marine Corps, Sironan Militia, and KSMC to produce a limited run of Jabbers for the UNSC Marine Corps to field test back on the Atlas moons under the designation of "M471." Despite being on a time crunch—with the Marines set to leave for the moons again by March 2544—KSMC was able to roll a set of twelve Jabbers off their production lines in under three weeks, delivering the vehicles to the UNSC to go on their way to one of the first true combat trials they'd face.

Atlas Moons Campaign (2544-2545)

Siege of Sirona (2544-2548)

Opening Days

Only a few months after the Jabbers left for the Atlas Moons, those that were left behind in militia control on Sirona saw combat of their own. On July 25, 2544, the Covenant launched an attack on Sirona, plunging the world into what would become a siege that lasted for nearly four years. The first combat that a Jabber saw during this conflict came a few days after the initial attack. By this point, Covenant forces had landed in Epona, just outside of the region's central city. While the bulk of the Covenant forces divided to both assault the central city and advanced down the western coast of the capital island, a third group split off to head east across the island to attack from the other side of Epona, using the engagements the other two forces had entered as a distraction.

HF Pang 1.9.jpg
Two platoons of M874 Pangolins supported a KSM1 Jabber in holding back advancing Covenant Forces during the early days of the Siege of Sirona.

This group primarily consisted of special operations Sangheili, using their small numbers and active camouflage to cross the island undetected. Arriving at a small town on the south-eastern border of the Epona farming community, these Elites found a trio of Jabbers engaging in live-fire exercises. Deciding that the vehicles would be a threat to any forces advancing along the east in hopes of catching the UNSC defenders in Epona off guard, the Elites managed to sabotage two of the vehicles before the remaining Jabber figured out what was happening and engaged the saboteurs to the best of its ability. However, despite this, the active camouflage gave the Sangheili the advantage and the situation looked dire for the Jabber, with the Elites setting an ambush for the vehicle as it covered the escape of the fleeing civilians. Right as the Jabber was about to fall victim to this ambush, however, a pair of mechanized platoons—consisting of eight M874 Armored Troop Transports—arrived, carrying a few dozen soldiers from SPECWAR Group SEVEN who had been running a live-fire exercise of their own nearby as part of the recovery process from injuries that saw them on the planet in the first place.

Recognizing that they couldn't hope to take on so many forces by themselves and that the alarm had probably already been sounded, the special operations Sangheili called for a larger assault to be called on the town and directly advance down the East coast, hoping to quickly overrun the position and surround Epona before the UNSC Air Force or Army forces on the island could react to the developing situation. As such, a collection of Phantoms was dispatched from the main forces, each carrying a Wraith and collection of Covenant forces. Deploying on the hill to the west of the town, the Covenant forces—about 150 troops in total supported by five Wraiths—moved to surround and take the town, with the ground forces advancing on the buildings with the Wraiths holding to the rear as indirect fire support.

By this point, a request for reinforcements had indeed been sent to the UNSC forces elsewhere on the planet, particularly to the militia base outside of Grannus and the UNSC Army's headquarters in the same area. However, with the fighting going on elsewhere and the HQ a good 300 kilometers away, support wasn't expected to arrive for several hours later. Thus, when the Covenant forces arrived outside of the town where the remaining Jabber, the eight Pangolins, and the Group SEVEN soldiers had set up defenses early in the morning of the third day of the siege, the defending forces would still need to hold out for about four hours before they received any additional manpower.

Thus, knowing they wouldn't be able to defeat the numerically superior force with the weapons and personnel they had available to them, the UNSC and Sironan Militia forces situated themselves for a prolonged defensive engagement. Taking advantage of the fact that the Covenant were advancing from the higher ground to the west, a contingent of soldiers set up among the low hills between the town and the advancing enemy forces. These soldiers, about a quarter of the total contingent, served to deter any Covenant forces advancing on the town on foot by utilizing guerilla tactics among the hills to ambush such advances and retreat to safety before retaliation could be dealt. Furthermore, the two Pangolins that had delivered these soldiers remained in a similar location, primarily driving amongst the hills to provide both fire support to and a distraction from the disembarked soldiers.

The remaining Pangolins and the Jabber set up closer to the town, on flatter ground. This area allowed the vehicles to make greater use of their mobility in avoiding shots from the Wraiths while also providing a clear target for the Jabber to target the Covenant armor. Additionally, their higher visibility led to the Covenant making several mistakes early on. First, it drew the fire of the Wraiths to targets at a far enough range away to easily avoid the shots, greatly dampening the impact the indirect-fire capabilities of the vehicles provide. Second, it drew a large contingent of the Covenant ground forces to advance from the elevated position in efforts to be able to take out the vehicles once the Wraith fire proved ineffective, drawing them into the trap laid by the soldiers and Pangolins among the hills.

The final line of defense for the town came from the remaining three-quarters of the soldiers scattered amongst the town itself. Using the buildings for concealment and cover, these UNSC forces could cover the Jabber and Pangolins along the flatter regions outside of the town from any Covenant that made it through the hills while also providing long-range support via snipers against the Covenant forces that remained to the rear. Though the latter advantage quickly disappeared with the Covenant leadership taking cover amongst the hills to avoid the sniper fire, the enemy wasn't so quick to react to what was happening to the forces they sent and a few waves of Covenant forces advanced on the position over the course of the first hour or so before the Covenant finally decided against this tactic. Over this same time period, while a pair of Jabbers had been taken out by lucky Wraith shots, the Jabber had also managed to take out two Wraiths in return and force the remaining vehicles further behind cover, protecting them at the cost of even less efficacy from their plasma mortars.

As a response, the Covenant changed up their tactics. Refocusing their mortar fire on the hills leading up to the town, the remaining three wraiths bombarded the area over the next hour, destroying the two Jabbers among the hills, killing many of the soldiers and forcing the rest to retreat to the open terrain in the process. Additionally, the Covenant set up forces along their flanks equipped with fuel rod guns, serving as an effective fence against several attempted advances by the Jabber and a Pangolin escort along the side of the area being shelled. The process continued for about another hour until the Covenant began a large scale advance once more, with the hills now cleared of UNSC forces and serving as cover for their own vehicles and only one additional Wraith being lost to the Jabber before the others reached the cover offered by the bumpy terrain.

As such, with no way of taking out the advancing Wraiths and the plasma mortar fire becoming more and more effective as they drew closer through the hills—two additional Pangolins were taken out, leaving only two left, and the Jabber suffered several near misses which began to compromise its armor—the UNSC forces were driven fully back into the city. With UNSC reinforcements still an hour or so away, the remaining troops dug in for what looked to be a desperate battle. Although the soldiers had come equipped with AM rifles—and even a few general purpose machine guns—they lacked any anti-armor capability, leaving the Jabber as the only effective defense against the Wraiths, a Jabber which was severely weakened and now out of its element of maneuverability and speed due to being hemmed in by houses and other structures.

However, this still proved to be enough of a deterrent that the Covenant forces held up among the fading hills close to the town, halting their advance and relying instead on indirect fire from the wraiths amongst the buildings of the town and occasional shots fired from fuel rod guns towards buildings that were found to house UNSC soldiers, though these attempts were quite effectively countered by the snipers amongst the town. Several flanking attempts by more standard Covenant forces were attempted, though these were cut down by the remaining two Pangolins supported by machine-gun nests established to the north and south of the village. Despite all these efforts by the defenders, however, their numbers were further cut down by the repeated bombardment of the area with minimal losses to the Covenant forces over the same time frame.

With thirty minutes left until the UNSC reinforcements arrived, both sides began to feel pressure to end the situation. The Covenant field leadership feared that they'd be unable to root out the UNSC defenders in time while the defenders, in turn, felt the opposite and feared they'd be destroyed in short order and the Covenant forces could secure a landing site that would allow them to advance on the east of Epona and have the city fully surrounded. As such, the Covenant called in for close air support from a nearby flight of Banshees. However, before the alien fighters could arrive in position to attack the holed up defenders, the humans made one last desperate assault, the hunkered-down soldiers providing fire support to suppress the fuel rod guns while the Jabber charged forward across the open field, flanked by the remaining two Pangolins as support.

With three, highly-mobile targets advancing on their position and infantry anti-armor support pinned by sniper and machine-gun fire, the remaining two Wraiths failed to take out any of the advancing vehicles before they crested the first hills. From this position, the Pangolins split off to distract the Covenant infantry with the fuel rod guns while the Jabber kept driving for the Wraiths, managing to get within the short range of the vehicles' mortar arcs. Within thirty seconds, the tank managed to land a killing shot on both vehicles. However, by this point, the fuel rod guns had made short work of the Pangolins and were closing in on the Jabber—now heavily damaged by the plasma hits it had taken on its charge—and the Banshees had arrived in the area, beginning their runs on the town. Though the Jabber was able to kill several more of the advancing Covenant forces it was eventually taken out as well, seemingly leaving the soldiers in the town without any armored or mechanized support against the Covenant aircraft and advancing ground forces.

Fortunately for the humans, though, the last charge of the Jabber and Pangolins had bought just enough time for the UNSC reinforcements to arrive. With several Warthogs leading the convoy and several Scorpion tanks taking up the rear, the Banshees were shot down or driven off and the remaining Covenant forces fled back towards the west of the island. With the town now reinforced, the UNSC advanced further up the eastern flank of the island, further locking it down from any future Covenant landings.

Role and Usage

Design Specifications



SGD920A1 Smoothbore Cannon

The main armament on both the KSM1 and KSM1A2 tanks is the 75 mm SGD920A1 Electrothermal-Chemical Smoothbore Cannon firing primarily a tungsten armor-piercing fin-stabilized discarding sabot round (APFSDS), but also possessing the capability to fire either high-explosive anti-tank (HEAT) or high-explosive squash-head (HESH) rounds, as well as canister shot. This cannon was designed specifically for the KSM1 as part of the original contract by Sironan General Defense, a small, locally founded defense contractor previously known for primarily servicing the needs of the planet's police forces. Due to the small caliber (despite the tank itself also being relatively small) a large number of rounds could be stored, with the KSM1 turret holding 60, the KSM1A2 holding 65, and 15 being located throughout the hull in both models. Finally, the tank could also fire anti-tank guided missiles, with up to five being stored along the Tank Commander's side of the turret, though these could only be manually loaded.

Originally planned to be a 7500 mm (100 calibers) gun, the final production model SGD920A1 had to be cut down to 6600 mm (88 calibers) due to issues with production capabilities and turret balance. While testing showed that the reduced barrel length did modestly affect muzzle velocity, the problems with mounting and production capacity proved to be more detrimental than the loss in potential penetration power, with the shorter gun still being able to penetrate analogues to Covenant armor at an acceptable engagement range. The final production cannon had a gun depression of 9 degrees and a gun elevation of 20 degrees when mounted in the KSM1 turret and a gun depression of 10 degrees and gun elevation of up to 22 degrees when mounted in the KSM1A2 turret. Additionally, it possessed an automatic stabilization system that could keep the gun level while driving at maximum velocity over rough terrain with enough precision to reliably hit targets out to its effective range in over 95 percent of cases during testing, with often better results seen during actual combat due to differences in engagement ranges and conditions.

The penetrator of the APFSDS round fired by the SGD920A1 comprised of a primarily tungsten alloy 17x395 mm penetrator. While tungsten on its own was considered largely substandard as a tank round by the designers of the vehicle, recent advancements in the years before the Human-Covenant War had led to the discovery of an alloy which possessed both the self-sharpening and incendiary effects of depleted uranium alloy penetrators without the innate toxicity, leading to increased penetration and the chance for potential additional internal damages once the round pierced the target. Combined with the approximately 2,450 meters per second muzzle velocity (just under the hypervelocity threshold) produced by the electrothermal-chemical propellant utilized for the APFSDS rounds for this cannon, the SGD920A1 firing APFSDS rounds could reliably penetrate analogues for Covenant armor out to 4,000 meters, though it has been anecdotally seen success out beyond this range when targetting more lightly armored vehicles.

For HE options, the SGD920A1 was provided with both HEAT and HESH rounds, though neither proved reliable against Covenant vehicles. For both, the small caliber and lack of rifling for the bore negatively impacted both explosive potential and accuracy (and subsequently effective range) respectively, though both shell types had the benefit of not losing penetration over distance as the standard APFSDS round would. However, they also proved to be significantly less effective at penetrating Covenant armor than the standard round, with the HESH round getting absorbed by the inherent spaced nature of Covenant armor and the HEAT round just not having enough explosive power behind it to break through the more heavily armored segments. Additionally, the existence of the fourth available shell type, a canister shot, overshadowed the anti-infantry uses of either HE round. As such, the HEAT and HESH rounds primarily saw usage as anti-fortification options, though the HESH performed significantly better for this role than the HEAT did due to the higher proportion of explosive material, leading to most tank crews choosing to take HESH rounds over HEAT rounds whenever they had the opportunity.

The final shell option for the SGD920A1 was a canister round. Unlike the canister rounds on the Scorpion, which fired a cylinder containing the eventual shot to be released upon impact, the canister round for the SGD920A1 worked much more like an oversized shotgun, immediately spraying roughly 80 small metal spheres out from the gun's barrel. This was particularly effective against nearby infantry units, though the relatively tight grouping of the shots allowed it to remain reliable out to about 250 meters. Once again, however, the canister round is limited in effectiveness by the smaller caliber of the SGD920A1, leaving the gun unable to fire as many projectiles as the Scorpion's cannon could.

In general, while the SGD920A1 offered more penetration and an incendiary effect on its primary armor-piercing round than the Scorpion's main cannon could, it proved to be less effective against fortifications and infantry than the larger tank while also doing less direct internal damage on penetrating hits due to the proportionally smaller projectile as a result of the discarding sabot nature.

One of the primary features of the SGD920A1 was its use of an automatic loading system, replacing the need for a fourth crewman in the vehicle. While the tank was still capable of being manually loaded in the event of an autoloader failure, with the breach remaining unblocked by the system when it wasn't in the process of loading a shell, this was considered an unlikely enough situation that the benefits of only having a three-man crew outweighed the possibility that the Tank Commander of Gunner would have to take over loading duties should it occur. To facilitate this emergency manual loading, access to the autoloader's ammunition tray was also available through a manually operated door behind the Tank Commander's seat.

The autoloader itself fed through a small opening in the rear of the turret to the ammunition compartment which remained sealed when a round was not currently being fed. This, compared with the door for manual loading, allowed for the ammunition to be separated from the crew-compartment, reducing the risk of crew loss in the case of a direct hit on ammunition when combined with emergency blow-out panels on the top of the turret's ammunition compartment. Within the ammunition compartment, 25 of the turret stowed rounds were available as "ready rounds" on the autoloader's cassette while the remaining rounds were located lower in the turret and would have to be fed onto the autoloader between combat encounters by the Commander through the access hatch. This system allowed more rounds total to be stored in the turret than would otherwise be available if all of them were connected to the autoloader. Additionally, the Gunner had the ability to rotate the cassette to select a particular round as part of the Jabber's fire control system.

The autoloader system had a minimum cycle of 4.5 seconds and a maximum cycle of 8 seconds for reload, depending on the current elevation of the gun at the time of being fired. This was due to the autoloader automatically disconnecting from the vertical stabilizer and returning to a level position to line up with the loading tray and rammer. Here, the spent casing was first ejected through an ejection port below the autoloader before the next round was cycled in. While this was occurring, the Gunner could still aim as, while the gun wouldn't respond until the process was complete, the Gunner's firing controls and sight were vertically independent of the gun, dictating where it went, rather than the gun dictating where they aimed. With calculations taking place during the aiming process, the only delay following loading was the gun moving back into position, which took no more than 3.5 seconds.

M68 Gauss Cannon (KSM1A2)

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An M68 Gauss Cannon mounted on a Warthog. This gun served as a second primary weapon onboard the post-war era KSM1A2 Jabber MBT.

The post-war KSM1A2 model of the Jabber also saw a second primary armament mounted coaxially to the right of the SGD920A1 cannon in the form of surplus M68 Gauss Cannons as the UNSC was looking into replacements for the older weapon. While only firing one type of ammunition when used by the Sironan Militia, the M68 became the primary anti-fortification weapon of the post-war Jabber due to the hypervelocity nature of the projectile it fired, with HEAT and HESH rounds not being provided to KSM1A2 Jabbers as a result. While this weapon didn't require any additional development in and of itself, its inclusion in the tank did directly lead to changes for the A2 compared to the original Jabber, primarily in a larger turret, both in width and height, and the incorporation of an additional ammunition compartment to the right of the tank to accommodate the rounds and loading mechanism for the gauss cannon, though the inert nature of the projectiles allowed this one to not be as significantly closed off from the rest of the tank. This compartment could store up to 80 rounds for the M68 on a continuous cassette system, allowing it to automatically reload the weapon. Additionally, the weapon was mounted on its side, with rounds loading into the top and being ejected down a chute contained within the turret towards the bottom right of the tank.

Firing 25x130mm high-density projectiles at up to approximately 13,700 meters per second, the M68 Gauss Cannon aimed to take advantage of hypervelocity impacts to damage the targets it hit. Rather than directly penetrating what it impacts, the extreme energies of the collision result in the projectile and its target behaving more like fluids than metals, with both vaporizing upon collision, often in large segments when it comes to the impacted target. These impacts can also often lead to plasma discharges as the air around the area is superheated, often making them easy to mistake as explosions when combined with the similar results they show. While typically utilized in an anti-vehicle role when mounted on Warthogs by the UNSC, this behavior actually led to it being primarily utilized for anti-fortification roles, as the SGD920A1 cannon provided more effective penetration and internal damage to vehicles with its APFSDS rounds while the M68 rounds could provide larger impact craters to leave a bigger hole in static structures.

When mounted on the KSM1A2, the M68 Gauss Cannon, by nature of being coaxial with the SGD920A1 cannon, had the same elevation and depression values. However, it fired significantly faster, with only an approximately two-second reload time.


Both models of KSM1 have two machine guns:

  1. A .50 caliber (12.7 mm) SSA223 Heavy Machine Gun on a remote weapons station located on the right side of the top of the turret, just in front of the Commander's hatch, controlled by the Tank Commander. This allows the weapon to be aimed and fired from inside the tank, providing increased protection for the Tank Commander when in a combat situation requiring its utilization. Developed by Sironan Small Arms in the later years of the Insurrection, the SSA223 was similar to the M247H machine gun used by the UNSC, albeit smaller and cheaper. The 223 also had a slower rate of fire (450 RPM) and a shorter effective range than its UNSC counterpart. However, testing by Kovac and Sons Motor Company and the Sironan Militia showed the weapon to be sufficiently effective within the expected infantry engagement ranges of the tank while being provided at a significantly cheaper cost. 750 rounds of ammunition were available for this weapon on the KSM1 and 850 were available on the KSM1A2.
  2. A 7.62 mm (.308 in) SSA107 General Purpose Machine Gun mounted coaxially to the left of the main gun. Much like its bigger sister, the SSA223, the SSA107 was comparable to the standard UNSC M247 machine gun, albeit smaller, cheaper, and with a lessened rate of fire (550 RPM) and a shorter effective range. However, the SSA107's specifications were also found to be within acceptable limits during testing. 4,500 rounds were available for this weapon on the KSM1 and 5,000 were available on the KSM1A2.


All Jabbers are equipped with a ballistic fire-control computer that uses both system and user-supplied data from a variety of sources to compute, display, and incorporate lead angle, range to the target, and selected ammunition type into one single firing solution for the Gunner, allowing the main gun to be fired accurately. Additionally, the Gunner has the option to use the computer to automatically select any of the shell types available in the autoloader cassette to prepare as the next round. Laser rangefinders, crosswind sensors, tracking rate tachometers, and static cant sensors, as well as situational data about shell type-dependent flight characteristics, tank-dependent bore alignment, and a variety of temperature-based effects are all incorporated into the computer's calculations to determine these three factors. This firing solution is updated at over one-hundred times per second and incorporated into the reticle on the Gunner's sight in all modes, allowing the Gunner to reliably hit the target by simply keeping the displayed reticle on it, vastly simplifying his or her job.

The Gunner's sight itself can view across a wide range of the electromagnetic spectrum, though the most commonly used settings are thermal and visual. While it is called the "manual sight" in its name, this only refers to the fact that the Gunner has the ability to use it manually, boresighted to the main gun and coaxially weapons, should the targeting system fail, not that he is required to aim manually using it. In fact, the sight is the primary method for the Gunner to aim the weapon even when using the fire-control computer and is the device onto which the targeting reticle is projected. In addition to the Gunner's sight, the Tank Commander can also get an external view of the tank using the Commander's Independent Multiwavelength Viewer (CIMV). This device, with the capabilities to cover the same wide range of the electromagnetic spectrum as the Gunner's sight, allows the Commander to locate targets and pass them on for the gunner to engage while the commander scans for new targets. The CIMV also links with the Commander's Weapon Station to aim and control the remotely operated SSA223 HMG should the need arise.

In addition to the two primary target-acquisition systems for the Commander and Gunner to utilize, both also have access to a passive sensor system to detect strong external emission signals that might indicate an enemy out to a maximum range of two kilometers, and the Tank Commander can activate an active air detection radar system to detect incoming aircraft.


Primarily designed to fight the Covenant and their plasma weapons, the tank varied from typical defense design in one important manner. While it remained a composite armor system, consisting of layers of Titanium A alloy, open space, plastics, and hardened ceramic blocks, the specific ceramic used was changed. While ceramics generally have the capability to resist high heats, the 3,000°C temperatures reported for some heavy Covenant plasma weapons required something with a higher melting point than the typical silicon carbide. As a result, the decision was made to instead utilize a form of titanium carbide, sintered into coherent plates. While the material was slightly denser and more expensive, the difference that would result in total weight and cost were negligible due to the small size of the Jabber. In turn, the material offered comparable hardness (important for shattering kinetic impactors) and a significantly higher melting point than the alternative, resistant to heat up to over 100°C beyond the highest recorded Covenant plasma temperature. While the armor would still have to deal with the concussive force from direct impacts or near misses from Covenant weaponry, this aspect of the attack was mitigated by the remaining layers of the armor, much like a HEAT shell's blast would be dissipated before making it to the interior of the crew compartment.

Another difference in the Jabber's design was the layout of the armor. While it was common to see tanks mount composite armor only on the front of the vehicle's hull and turret, the decision was made to also cover the entire top hull of the Jabber. This was a design choice intended to bolster two factors of the KSM1's intended role: the ability to work within an urban environment and the ability to directly face Covenant forces. For the former factor, the increased armor on the top of the tank served as additional protection against attacks from above. For the latter case, the decision was made specifically to counter indirect fire methods that the Covenant often deployed, specifically from vehicles such as the Wraith or Revenant. In addition, the sides of the turret and the spaced armor skirting placed along the exterior of the Jabber's tracks were both constructed from a composite, though these components made use of the lighter silicon carbide construction to cut down on weight in less vulnerable positions. The remaining faces of the tank's armor consisted of simple Titanium A armor plates, serving only to protect against smaller arms fire, with the decision made to cut down on weight and increase the vehicle's mobility.

Upon receiving additional funding in the post-war era, the Sironan Militia up-armored the KSM1A2's larger turret through increasing the thickness of the turret's side armor and implementing silicon-carbide composite armor on the rear. This decision was made following an investigation into the Jabbers that had been knocked out during the Human-Covenant War which had revealed that a large number of Jabbers had been disabled due to Covenant indirect-fire plasma weaponry impacting the rear of the tank, behind the turret. Upon impact, the simple Titanium A plating proved insufficient to disperse the force from the plasma before it could ignite the ammo stored inside, rendering the vehicle inoperable. While the doctrine of the militia to make use of the Jabber's mobility and have it advance under the arch of the incoming plasma and close the gap caused this situation to occur more often, the fact that this doctrine proved successful for Jabbers that avoided such impacts led to the decision to armor the rear of the turret against the plasma, rather than change strategies to something that avoided the hit in the first place.

Also making use of the increased post-war funding, the Sironan Militia began upgrading existing KSM1 and new KSM1A2 tanks with slat armor over the rear of the tank's hull. These served to disperse the containment fields of plasma weaponry and decrease their effectiveness before reaching the actual hull of the vehicle without needing to add a significant amount of weight to the design. In addition, tests were conducted into magnetic field generators to actively disrupt these containment fields from a larger distance in a sphere around the entire tank, but these systems did not prove cost-effective and were only implemented on a handful of KSM1A2s before the program was shut down.




The Jabber comes equipped with the proprietary Kovac and Sons Morvarc'h Hydrogen Fuel Cell/Electric Motor System. This system consists of an array of hydrogen fuel cells found in an isolated compartment to the rear of the tank providing electricity to drive a pair of motors at a combined maximum 2,012 shaft horsepower (1,500 kW) in the constant power range of the motors above 3,000 RPM and a combined maximum torque of 3,522 foot-pounds (4,775 Nm) in the constant torque range below 3,000 RPM. Due to the nature of electric motors, these are connected to the drive wheels at the back of the vehicle's track through a single-speed 10:1 step-down transmission, with reverse managed by electronically triggering the electronic motors to spin backward, driving the tank up to an electronically limited maximum speed of 20 mph (32 km/h). This system is capable of obtaining an electronically limited maximum speed of 50 mph (80 km/h) on paved surfaces falling down to 35 mph (56 km/h) cross-country. While theoretically higher speeds are possible with the electronic limiting system disabled, increased risks of crew injuries, higher maintenance requirements, and the lack of practical use of higher speeds in previous combat situations have seen the limiter remain enabled on the vast majority of KSM1 tanks.

While there were originally concerns about the power demands of the tank, with the electronic systems of the vehicle requiring electricity even while the motors aren't running and the motors themselves demanding extensive electrical draws from the fuel cells when they are, the large configuration of fuel cells taking up the rear compartment of the tank covers for this, allowing for a maximum range of approximately 450 miles before requiring refueling, or over three days of continuous idle running of the tank. Additionally, the lack of byproducts except for pure water (collected in a tank beneath the vehicle's fuel cell compartment) allows the tank to operate without an exhaust system, allowing infantry to operate close to the tank without potential for injury due to high-temperature or high-velocity gas emissions. Furthermore, the electric motors run significantly quieter than traditionally fueled engines while also requiring less maintenance as a whole due to the decreased complexity of the design, lacking automatic transmission fluid and motor oil as well as having generally fewer components as a result.

The fuel cell compartment of the KSM1 tank is flooded with an inert gas to counteract the inherent flammability of the fuel cell technology should it get struck by enemy fire. Additionally, this serves to remove the chance of any incident fires sparking as a result of the high temperatures (150 to 200 degrees F) that the fuel cell array operates at. This excess heat is radiated mostly through the rear bottom of the tank, allowing the temperature of the resultant heated air to decrease significantly before reaching a point where it could potentially cause injury to accompanying infantry or the tank crew itself. While the fuel cell array itself has a continuous operation lifetime over up to 50,000 hours, the mileage lifespan of the electric motors is more commonly the limiting factor determining when a Jabber's power system requires maintenance, repair, or replacement, typically only offering a lifespan of just over 30,000 miles.


Refueling the Jabber can be done through two methods. The primary method of refueling is to make use of a dedicated refueling facility to pump oxygen and hydrogen directly into the vehicle through a pair of ports to the rear left of the tank. However, if this is unavailable, the Jabber can connect to a wide variety of power sources to directly convert stored water to usable fuel through electrolysis carried out by an internal system connected to the water tank. The port for this connection is located to the rear right of the tank. A portable solar panel system is carried on the majority of Jabbers, capable of generating ten miles worth of fuel an hour on sunny days, designed to provide a method to temporarily refuel a Jabber if it was driven to a standstill without static refueling or power generation stations within range, though this situation proved rare due to the warning issued by the KSM1's fuel management system as the fuel cells came closer and closer to empty.


The Jabber runs on 6, 750mm road wheels per side, each mounted on an independent hydropneumatic suspension unit. While these suspension units are active, with hydraulic actuation, they are often independently set prior to installation based on expected terrain and load to reduce the strain on the tank's hydraulic pump via a reduction in the actuation required to account for uneven roads. However, the benefits of doing so are relatively minor due to two factors. First, the front road wheels of the Jabber are lifted off the ground during turns below about 10 miles per hour (above which the extra stability is judged to be a more important factor) in order to reduce track contact with the ground and allow for quicker turning and reduce maintenance requirements on the tracks. Second, the actuation can be manually controlled by the driver to afford the tank extra gun depression or elevation by making the vehicle "kneel" (raise the rear and lower the front) or "crouch" (raise the front and lower the rear) respectively. As such, the vehicles very often saw heavy use beyond adapting to the terrain from their initially set position.

The drive sprocket resides in the rear of the Jabber, with the front wheel serving simply as a guide wheel and to provide tension. This was mostly due to the location of the fuel cells and electric motors in the rear of the vehicle, but also served a purpose as the tank saw use and the tracks lost tension and lengthened over time. It was considered better by KSMC to allow the resulting slack to be pulled by the rear wheel and thus reside on the top portion of the track, draping along the return rollers, than to force the track to be pulled from the front and thus have the slack reside along the ground. This also resulted in less of the track being under full tension and thus reduced wear.

Hydropneumatic supsension.png
A conceptual drawing of a hydropneumatic suspension system like that found on the Jabber.

The hydropneumatic units themselves consist of a suspension sphere—connected to the tank's hydraulic fluid reservoir and pump via a suspension cylinder—which contains a volume of nitrogen (due to its lack of corrosive properties) trapped and separated from the hydraulic fluid via a rubber membrane. While the hydraulic fluid itself is incompressible mineral oil (to avoid water bubbles), the hydrogen can compress and expand with changes in pressure and thus acts as the spring for the system. Crucially, this spring mechanism behaves with non-linear force-deflection characteristics, allowing the suspension systems to easily avoid eigenfrequencies that may amplify or continue variations in the terrain into the tank itself as a linear spring system would be at risk of. This removes the need for additional dampening systems and is a critical part of the unit's relative lack of complexity and ease of maintenance or replacement. The leveling is controlled via automatically adjusting the amount of hydraulic fluid in the sphere, with the "kneeling" and "crouching" positions, as well as the lift of the front wheels during turning, special implementations of this process.

Tank Desant

Although the KSM1 is not designed to easily carry riders in the same way the Scorpion was, with the upper rear of the tank's hull being not only small but also often uncomfortably hot due to the operating temperatures of the hydrogen fuel cell system, (even accounting for the directional cooling system) provisions can be made to allow the Jabber to carry a small number of infantrymen in tank desant. This is achieved by locking the turret forward and utilizing ropes and equipment straps to provide handholds on the flat front upper hull of the tank. However, Sironan Militia doctrine does not recommend this strategy due to the exposed position it places the infantry in and the limitations it puts on the ability of the tank to quickly fire upon spotted enemies. Additionally, if the mounted individuals are not aware of where they are positioning themselves, they can often block the driver's view. As a result, this tactic was not often seen used by operators of the KSM1 tank.

Strategic Mobility

Contrary to the tactical mobility inherent to the tank itself and how it navigates the battlefield, strategic mobility is the ability of multiple vehicles to arrive in a timely, cost-effective, and synchronized fashion. For the Sironan Militia, this wasn't a major concern due to the nature of the force, with a focus more on quick but local defensive reactions. As such, the inherent mobility of the KSM1 proved effective enough to get the tanks into positions to respond to advancing threats within the standards expected of militia readiness. For the UNSC, however, the few KSM1s that they operated received slight modifications to address apparent deficiencies in strategic mobility of the vehicle compared to the Scorpion.

Particularly, while the vehicle was smaller and lighter than the Scorpion, considerations had not been made for air-lift capabilities. As such, production KSM1 tanks, in both the original and A2 configurations, lacked attachment points to allow UNSC dropships, such as the Pelican, to carry the vehicle beneath their tails. Additionally, the Jabber lacked compatible points to which clamps could attach to the floors of UNSC frigate vehicle bays for atmospheric deployments. Both of these features were easily added, however, to UNSC models and few other changes proved necessary, with the size and weight remaining within the confines of what the UNSC was capable of transporting effectively.

However, for a significant portion of original KSM1 tanks on Sirona, particularly those on the capital island, both militia and UNSC operated, saw the addition of attachment points for an amphibious conversion system. This was a temporary air cushion and propellor/rudder system that could be attached to the outside of the tank to allow it to deploy from Wet Fleet landing craft without submitting the landing craft themselves to shore-based fire. This system was later discontinued for the KSM1A2 after the Siege of Sirona proved that such amphibious capable craft proved less effective than simply transporting the vehicles over bodies of water through air-lifting them with Pelicans. Another factor in this decision was that Sironan Militia Jabbers saw minimal movement between theaters during the siege, typically remaining to defend their original position as per the doctrine of the militia as a local defensive supplement to the more mobile UNSC.

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