Army Upgrading Medium Caliber Cannons, Ammo

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While many U.S. combat vehicles are still armed with the 25mm Bushmaster, it’s estimated that more than 100 countries — including peer- and near-peer competitors — currently integrate cannons from 30mm-57mm that could potentially be used against U.S. armored and Stryker brigade combat teams.

Recognition of this evolving reality has been one contributing factor to several recent developments involving U.S. “medium caliber” cannon and ammunition systems.

One example can be seen in the Stryker “Dragoon” upgrade applied to 83 Infantry Carrier Vehicles in the Army’s 2nd Cavalry Regiment Stryker Brigade Combat Team. Based on a March 2015 operational need statement, the modification features the introduction of a turreted 30x173mm XM813 cannon, a derivative of the Mk44 30mm cannon, to approximately half of the vehicles in the regiment’s rifle and scout platoons. The entire upgrade provides the ability to detect, identify and defeat a broader target set at greater ranges.

Lessons learned following the Dragoon fielding caused the Army to move forward with efforts to enhance lethality for a greater portion of the Stryker fleet. Those efforts led to the May 2019 award of multiple contracts for the Stryker Medium Caliber Weapons System lethality program, under which teams integrate a weapon station using a government-furnished XM813 gun on a government-furnished Stryker DVHA1 Infantry Carrier Vehicle.

Along with new cannons like the XM813, a number of companies are providing new supporting ammunition designs. Several representative examples can be found at General Dynamics Ordnance and Tactical Systems.

In terms of 30x173mm ammunition for the upgunned Strykers, Moises Gutierrez, business development director at GD-OTS, said the current ammunition inventory for the Stryker Dragoons reflects derivations of Navy legacy ammunition, like the Mk258 Armor Piercing, Fin Stabilized Discarding Sabot-Tracer, or APFSDS-T, “that have been optimized for fielding” to the 2nd Cavalry Regiment.

In addition to that optimized ammo, he pointed to three new 30x173mm ammunition developmental programs currently underway.

The replacement for the Mk258 APFSDS-T is designated as the XM1170, explained Alan Perkins, chief technology officer for munition systems at General Dynamics Ordnance and Tactical Systems.

The training round to go with it is the XM1172, which will replace the current Mk317 Target Practice, Discarding Sabot–Tracer and the Multi-Function Munition round, which is an “airburst” 30x173, Perkins said.

Initially the Army had planned on an XM1171 as a High Explosive (HE) version and XM1173 and a Target Practice-Tracer to go with it, along with the airburst rounds. But rather than have all three, the service has decided to table the XM1171 conventional HE and just have the HE Airburst, he added.

Ultimately, once those requirements are nailed down for the Multi-Function Munition High Explosive Airburst the Army will put together the requirements for the corresponding training round to go with it, Perkins said.

Another example of weapons upgrades comes from Nammo AS, which has highlighted U.S. adoption of its Mk258 Mod 1 APFSDS-T “Swimmer” round, featuring “super cavitation” that combines armor piercing with the ability to shoot through water.

“We can confirm that together with our partners in General Dynamics, we have already shipped tens of thousands of rounds for use not only by the Stryker Dragoons of the U.S. Army, but also the U.S. Navy’s San Antonio-class, and the littoral combat ships, all of which are fitted with these [30x173mm] weapons,” said a Nammo company representative.

“The fact that the ‘Swimmer’ has been adopted by both the Army and the Navy, and for such a wide range of platforms, really speaks to the performance of the ammunition. Through years of testing we have demonstrated that the ‘Swimmer’ is effective both against fast moving surface and sub-surface targets, as well as modern armored vehicles,” the representative added.

Rylan Harris, program director for advanced ammunition at Northrop Grumman Armament Systems, highlighted his company’s cutting edge advanced ammunition technologies being applied in multiple calibers across what he described as three lanes: programmable ammunition; proximity sensing ammunition; and guided ammunition.

As an example of programmable ammunition, he pointed to the company’s 30mm programmable airburst design, which stems from the Mk310 airburst round, which was initially developed under the Marine Corps Expeditionary Fighting Vehicle program, he said. That vehicle carried the Mk44 30mm cannon. “We have kept up the ammunition technology and are now working with the Army to keep that technology qualified and scalable to other calibers,” he said.

Describing how the round provides the ability to engage targets in defilade, he added that the company is currently working with the Army to field the round on 2nd Cavalry Regiment Stryker Dragoons in 2021.

Harris said the initial fielding will retain the Mk310 designation, but that Northrop Grumman “is also in development/qualification with the Army for their own variant, that will carry an Army ‘XM1182 HEAB-P’ [programmable] designation.”

While the Mk310 programmable design requires the round to be preset before firing, Harris observed that the proximity technologies require no preset, using a sensor package on the round instead, while the company’s guided ammunition development efforts apply some of the proximity technologies coupled with a spinning aft end-design to create drag and guide the bullet.

“Essentially we have taken the technology we developed for our large caliber [artillery] Precision Guidance Kit and evolved it for application to medium cal,” echoed Mike Hafften, director of business development for ammunition at Northrop Grumman Armament Systems. “Through internal investment we are able to scale and adapt that technology to rounds anywhere from 20mm to 57mm.”

One cannon application that has led to confusion in some circles is the recent integration of small numbers of the 30x113mm “Lightweight 30mm” cannon with a number of ground systems. Derived from the M230 cannon on the Apache helicopter, the lightweight design allows possible application on a wide range of both manned and unmanned ground platforms.

Regarding 30x113mm ammunition activities, Perkins pointed to an ongoing effort to turn the current M789 High Explosive Dual-Purpose round “into a more effective proximity-type munition rather than the conventional point detonation that you get today,” Hafften said.

“The gun would provide a signal for the round to either detonate in a point detonation mode or in a proximity mode,” he explained. “It’s a user-driven requirement where you would basically get lethal effects 2 to 4 meters above the target rather than right on the target.”

He added that current intent is to have a demonstration of the new capability by the end of this year.

Some of the most recent activities in medium caliber cannons relate to the introduction of the Army’s new XM915 50x228mm, which has been developed with an eye toward the Army’s future Optionally Manned Fighting Vehicle program, also known as OMFV.

According to John McCollum, director of business development at Northrop Grumman Defense Systems’ guns operating unit, the Army’s Combat Capabilities Development Command Armaments Center is continuing to fund the company’s efforts to mature and qualify the cannon to have it ready for insertion on the OMFV platform.

As of press time, four XM913 cannons have been delivered to the government with an additional seven projected for delivery in November. Current industry expectations include a follow-on contract that will cover support of 10 XM913 cannons in 2021, two XM913 feeders, developing the XM913 Gun Control Unit and Airburst Munition contact set as well as upgrading the cannon fleet to one common configuration.

Early government testing led to recognition of areas where the company could evolve the cannon design to make it more robust, McCollum noted.

“One of the areas they have asked us to look at is a slight modification to the barrel, as far as the center of gravity,” he said. “Another is to also look at an improved muzzle brake design that would reduce wear and extend its life.”

He continued: “But the gun is functioning and firing lots of rounds. So the way I would characterize all of those slight design changes is that the gun is already [Technical Readiness Level] ‘6-plus,’ so we’re down to the real refinements of portions of the design.”

Acknowledging that OMFV requirements might be opening up to other potential cannon solutions, McCollum said, “I think the community, including the next-generation combat vehicle cross-functional team, still has a very high level of interest in the XM913 as the primary solution for the platform. And the reason for that is the range and the standoff that it will give the combat formation compared to [other solutions]. That, combined with the reliability of the Bushmaster cannon design, I still think makes it a strong choice.”

As with the 30x173mm, General Dynamics’ Perkins outlined similar activities surrounding the ammunition suite for the new XM913 50x228mm cannon.

There are three variants: a 50mm APFSDS; a 50mm High Explosive Airburst similar to the Multi-Function Munition; and a standard Target Practice-Tracer training round, he explained. The TP-T and the APFSDS are government-owned technical data packages that have been in development for a few years as is the case for the High Explosive Airburst warhead.

Perkins noted that development of the three rounds is taking place in parallel but that the TP-T, by nature of being a training round, is slightly ahead of the tactical munitions, which he described as “more in the development phase, working out the particulars on the design to optimize reliability and producibility.

“There is also a need to use some of those TP-T for the platform development, so we are producing some of those right now at a fairly high volume and feeding them to the Army so that they can, in turn, feed them to the platform developers,” Perkins said.

Reviewing the three 50mm round designs, Northrop Grumman’s McCollum added that his company was recently awarded a three-year development contract for the airburst round, with a Milestone C decision currently projected for the fourth quarter of calendar year 2023.

“A key thing about our 50mm offering is that it does leverage the same fuze and a lot of the same capabilities that we are integrating into the 30mm Stryker, so we see commonality from the 30mm implementation to the 50mm implementation,” McCollum added.

Asked about primary advantages of moving future platforms up to the 50mm XM913, he was quick to credit the larger caliber system with “hands-down lethal overmatch,” observing, “If you physically look at the 30mm round next to the 50mm round it’s a phenomenal difference just in terms of size. And the benefits that larger projectile can bring in an airburst configuration with that larger warhead are significant.”

Topics: Army News