Following the trend of U.S. Navy ‘containerized’ solutions for various platforms, BAE Systems is pitching its Bofors 40 Mk 4 as another containerized system for counter-UAS, counter-USV, and point-defense missions. The gun was shown for the first time at Sea Air Space 2025 as part of a broader effort to introduce the gun and its ‘3P’ all-target ammunition to the U.S. audience.
The U.S. Navy is leaning heavily into palletized and containerized solutions for additional firepower on lightly armed surface combatants. The U.S. Navy’s Littoral Combat Ships, long considered under-gunned for a near-peer conflict, are one of the main recipients of containerized weapon systems for this purpose. Other ships, like expeditionary sea bases and amphibious assault ships, could get containerized guns that can roll out from hangars to provide air defense during complex attacks, adding to the point defense and precision kill capabilities of the entire fleet.
A containerized launcher seen on USS Nantucket, a Freedom-class LCS, during its commissioning in November 2024. BAE Systems is looking to capitalize on U.S. Navy interest in similar containerized launchers. Screen capture.
BAE Systems has recognized the emerging need, pitching their 40mm Bofors 40 Mk 4, alongside other solutions, as a suite of options for a U.S. Navy interested in firepower that can be quickly onloaded and offloaded from any ship in the fleet.
BAE is offering a wide range of palletized weapon solutions to the U.S. Navy, including the Adaptable Deck Launcher (ADL), high power microwave systems, and of course, the 40 Mk 4 gun. Naval News had the opportunity to discuss the gun and its unique ammunition in detail with Tate Westbrook, Director of Naval Guns & Ammunition and Surface Ship Missile Launchers at BAE Systems.
The Bofors 40 Mk 4 seen on the show floor in its deck-mounted configuration. Photo by author.
The U.S. Navy, in its operations in the Red Sea, has expended a large number of medium and long range surface-to-air missiles like the SM-2 and SM-6 in defense of allied warships and international shipping. Despite upgrades to existing weapons to improve the drone threat, the U.S. Navy is still concerned with the emerging drone threat, prompting interest in additional platforms for counter-UAS and counter-USV missions.
We brought the 40mm gun to Sea Air Space this year because earlier this year, the U.S. Navy asked us to provide options for palletized weapon systems. The key to defending any warship at sea is the concept of layered defense. The ability to engage threats, at medium and short range with naval guns, is an essential part of why we brought the 40mm Mk 4 to the show.”
The ammunition fired by the 40 Mk 4 is unique in the fact that it operates with a highly effective proximity fuse. This allows for near-misses or general targeting of an incoming drone, missile, or surface ship with a kill box several meters in size. The platform is also superior to the U.S. Navy’s existing 20mm Phalanx CIWS, making replacement of the Phalanx with a guided point-defense system possible if the U.S. Navy pursues the system fully. Westbrook explained the superiority over 20mm gun systems, emphasizing range differences and ammunition type.
The ratio of size to projectile propellant reminds us that the effective range of a 40mm cannon is four times the range of a 20mm gun.”
Westbrook displaying the ‘3P’ ammunition during an interview with Naval News.
The ammunition used is nicknamed ‘3P’; proximity-fused, pre-programmed, pre-fragmented. The 40mm projectiles are extremely effective against all types of aerial threats, including high speed ‘FPV’ style drones performing evasive maneuvers. The gun was able to shoot down several types of UAS with ‘one-shot, one-kill’ performance during trials.
The size of the projectile itself provides the room for a robust seeker and significant quantity of high explosive, or 1,100 tungsten spheres that provide a kill box, per round, of several meters at range.
The gun also performs at a high rate of fire despite the larger caliber, firing around 5 rounds per second in all modes. This allows for sustained fire against drone swarms and other emerging threats like USVs or swarming small boats, rapidly switching targets to engage inbound threats.
“The gun has a remarkable rate of fire at 300 rounds per minute, so it’s optimized for air defense with anti-surface and anti-vehicle capability as well.” Said Tate Westbrook, BAE Systems
According to Westbrook, the gun performs out to 4-5 kilometers, which is extremely effective for a 40mm gun. To sustain the rate of fire the gun can be reloaded, enabling a sustained fire rate against drone swarms with several hundred targets.
The programming and loading displays seen in the rear of the gun, where ammunition is loaded, unloaded, and programmed for engagement. Photo by author.
“The deck mounted gun contains 70 projectiles in the drum, as well as 30 rounds on the cannon. A total of 100 rounds against drone targets gives you 40-50 stowed kills before reload. With a cruise missile threat, it gives you 12-15 stowed kills prior to reload depending on the speed of the incoming missile. Sailors below deck can be continuously loading rounds while the gun is firing.” said Tate Westbrook, BAE Systems
A palletized version of the gun is being sent to Ukraine to provide air defense systems as it continues battling Russian Shahed-style one-way attack drones. According to Westbrook, the palletized version of the 40 Mk 4 can be installed on any combatant or non-combatant ship in a non-intrusive way for self defense against missiles, drones, and small boats. Guns can be loaded and onloaded in just a few hours.
“The palletized version operates with a dedicated electro-optical site for any non-combatant ship, marketed as the TRIDON Mk2.” said Tate Westbrook, BAE Systems.
The U.S. Navy’s pursuit of palletized and containerized firepower is making up for the ongoing loss of VLS cells in the fleet as the Ticonderoga-class guided missile cruisers retire. Current containerized missile programs have made the Freedom- and Independence-class ships easily reloadable at sea to fire any type of Mark 41-capable missile. The options offered by BAE Systems could extend this lethality enhancement to every U.S. Navy ship.
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