U.S. Navy Expands 30mm Anti-Drone Gun Fleet to Strengthen Warship Close-In Defense.

The U.S. Navy is expanding its Mk 38 Mod 4 30mm gun inventory to give warships a lower-cost option for defeating drones and other small threats without relying immediately on expensive surface-to-air missiles. The latest production tranche adds 22 Mk 88 Mod 4 mounts, while current public procurement reporting places cumulative Mk 38 Mod 4 production orders at 55 mounts when earlier buys are included.

The shift addresses a growing operational problem highlighted by sustained combat operations in and around the Red Sea: relatively inexpensive unmanned threats can force warships to expend much costlier, more limited missile inventories. By adding a 30mm weapon with airburst capability, improved sensors, and Aegis integration, the U.S. Navy is strengthening the inner layer of ship defense while preserving surface-to-air missiles for cruise missiles, ballistic missiles, and other threats requiring greater range and interception performance.

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A Mk 38 Mod 4 30mm gun fires during a live-fire exercise aboard the Arleigh Burke-class guided-missile destroyer USS Mustin (DDG 89) in the South China Sea on April 17, 2026. (Picture source: U.S. Department of War/Defense)

Under the first year of the new contract, the U.S. Navy committed $61.3 million for 22 Mk 88 Mod 4 stabilized gun mounts and 23 Mk 48 Mod 2 electro-optical sights. MS International, parent company of MSI-Defence Systems US, disclosed those quantities on October 1, 2026, after the Pentagon’s contract announcement identified the overall value but did not state the number of mounts included in the first-year order. The three-year agreement has a potential value of approximately $197 million and covers Mk 88 Mod 4 mounts, Mk 48 Mod 2 sights, associated equipment and spares, with deliveries extending into January 2031.

Quantities for the remaining contract years are to be agreed annually, meaning additional production orders could follow beyond the 22 mounts already committed during the first year. The reported total of 55 mounts should not be interpreted as 55 equipped ships. That figure reflects the cumulative number of production Mk 38 Mod 4 mounts reported as ordered across successive procurement actions, including the latest tranche.

USS Mustin, an Arleigh Burke-class guided-missile destroyer, was the first U.S. Navy warship to receive the Mk 38 Mod 4 and remains the only destroyer publicly identified in current reporting as carrying the weapon. The ship received two mounts, reinforcing why the reported 55-mount procurement total cannot be converted directly into an equivalent number of destroyers. Installation schedules will depend on ship configuration, maintenance periods and integration priorities.

The Mk 38 Mod 4 represents the first caliber increase for the Mk 38 family in more than three decades. Earlier variants use the 25mm M242 Bushmaster chain gun, while the Mod 4 incorporates Northrop Grumman’s 30mm Mk 44 Bushmaster II, providing greater destructive effect and a more capable engagement envelope against small surface and airborne targets. The weapon carries 400 rounds through two ammunition feeds, allowing operators to switch between ammunition types without manually reloading the gun.

Its ability to employ 30mm airburst ammunition is particularly relevant against small unmanned aerial vehicles because the engagement does not depend solely on direct projectile impact against a small, maneuvering target. The upgrade also extends beyond caliber. The Mk 48 Mod 2 electro-optical sight provides stabilized television and thermal imagery with laser ranging, while integration with the Aegis Combat System allows compatible destroyers to incorporate the weapon more effectively into the ship’s wider sensor and engagement architecture.

This combination of Aegis cueing, electro-optical tracking, and 30mm airburst ammunition gives the Mk 38 Mod 4 a different operational role than a simple replacement for the older 25mm gun. U.S. Naval Sea Systems Command has linked development of the Mk 38 Mod 4 to the growing threat from unmanned aircraft and high-speed maneuvering unmanned surface vessels.

During testing at the Potomac River Test Range in July 2022, the U.S. Navy demonstrated detection, tracking, and live-fire engagement against aerial and surface targets, showing the weapon’s ability to operate through an integrated fire-control chain. Those demonstrations establish the intended counter-unmanned capability but do not by themselves confirm a combat kill against a hostile drone. Publicly documented Mk 38 Mod 4 firing remains centered on developmental testing and live-fire training.

The operational case for the system has become more compelling as U.S. Navy destroyers have faced repeated drone and missile attacks in the Red Sea region. Such engagements create a magazine-management problem because vertical-launch cells carry a finite number of interceptors, and replenishing those weapons at sea remains far more complicated than replacing gun ammunition.

A 30mm cannon cannot replace Standard Missiles, Evolved Sea Sparrow Missiles, or other longer-range components of an Aegis destroyer’s air-defense architecture. Its value lies instead in adding another layer to the defensive sequence, allowing commanders to use a gun-based option against suitable close-range threats and preserve higher-end interceptors for targets that demand their speed, range and guidance performance.

That distinction becomes increasingly important during sustained operations. A low-cost unmanned aircraft can impose a disproportionate defensive burden if every engagement requires a sophisticated missile, while a 30mm weapon offers a more favorable cost-per-interception option when the target enters its effective engagement envelope. The result is not simply lower expenditure per shot, but greater endurance for the ship’s overall air-defense magazine.

The Red Sea experience has underscored this requirement. U.S. Navy warships may need to confront inexpensive drones, unmanned surface vessels, cruise missiles and ballistic missiles within the same operational environment, making it increasingly important to match each threat with the least resource-intensive weapon capable of defeating it.

The Mk 38 Mod 4 therefore represents more than a shift from 25mm to 30mm firepower. By combining the Mk 44 Bushmaster II, dual ammunition feeds, airburst ammunition, stabilized electro-optical tracking and Aegis integration, the system gives the U.S. Navy an additional inner-defense option designed for the economics and saturation pressures of modern drone warfare.

With 22 additional mounts confirmed in the first year of the new contract and public procurement reporting placing cumulative production orders at 55 mounts, the Mk 38 Mod 4 is moving beyond its initial installation aboard USS Mustin toward a potentially broader fleet role. Its strategic value lies in strengthening layered ship defense while helping U.S. Navy commanders preserve finite and expensive missile inventories for the threats that require them most.

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Written by Alain Servaes – Chief Editor, Army Recognition Group
Alain Servaes is a former infantry non-commissioned officer and the founder of Army Recognition. With over 20 years in defense journalism, he provides expert analysis on military equipment, NATO operations, and the global defense industry.