Diehl and BAE Systems Move to Qualify Mk 45 Gun for 80 km Vulcano Rounds and Ship-Launched IRIS-T.

Diehl Defence and BAE Systems are moving to qualify Diehl’s 127 mm ammunition for the Mk 45 Mod 4 naval gun while studying the integration of IRIS-T missiles with BAE shipboard launchers. Announced on August 3, 2026, the effort could give NATO and partner navies longer-range naval gunfire and a new European option for shipborne air defence.

The ammunition work aims to extend the reach and flexibility of a widely used naval gun, while the missile study will assess whether an IRIS-T variant can be adapted for maritime threats. No contract, warship program or integration schedule has been confirmed, but the cooperation reflects growing demand for stronger naval firepower and layered air defence.

Related topic: Netherlands Advances Uncrewed Sonar Vessel for New Anti-Submarine Warfare Frigates.

Diehl Defence and BAE Systems are working to integrate Vulcano 127 mm guided ammunition with the Mk 45 Mod 4 naval gun and assess IRIS-T missile integration with shipboard launchers, aiming to expand naval strike range and air-defence options (Picture source: U.S. DoW).

The Mk 45 Mod 4 is a 127 mm, 62-calibre automatic naval gun, meaning that its barrel is 62 times the bore diameter, or approximately 7.87 metres. The Mod 4 differs from earlier 54-calibre Mk 45 guns through its longer barrel, strengthened mount, digital control system and modifications intended to accommodate ammunition generating approximately 50 percent more firing energy. The U.S. Navy lists a firing rate of 16 to 20 rounds per minute from a 20-round automatic loader. Conventional ammunition has a published range of 13 nautical miles, approximately 24 kilometres, while BAE Systems states that specialized cargo ammunition can exceed 20 nautical miles, or 36 kilometres. Magazine capacity depends on the ship: U.S. Arleigh Burke-class destroyers carry up to 600 conventional 127 mm rounds, while Ticonderoga-class cruisers were designed for 1,200 rounds divided between two guns. These figures illustrate the gun’s principal advantage over missiles: a warship can carry hundreds of projectiles and sustain repeated engagements without consuming limited vertical-launch cells.

Diehl’s principal contribution is the Vulcano 127 family, developed with Leonardo in unguided Ballistic Extended Range and guided Guided Long Range configurations. The guided projectile uses satellite-aided inertial navigation for flight toward programmed coordinates and can be fitted with terminal guidance options. Diehl has qualified a semi-active laser seeker for targets illuminated by an external designator and a far-infrared seeker for autonomous terminal acquisition. A height-of-burst configuration is available for area effects. The warhead is an insensitive multipurpose design containing preformed tungsten fragments, intended for personnel, unprotected and lightly protected vehicles, field positions and infrastructure. The projectile’s sub-calibre, low-drag configuration permits Diehl to claim a maximum range of 80 kilometres from a 127 mm gun. That figure is an upper design range rather than a guaranteed engagement distance under every condition; accuracy and terminal effect will depend on trajectory, weather, target location error, guidance availability and the selected fuze or seeker.

Germany has already completed much of the qualification work for Vulcano, but only with Leonardo’s 127/64 Lightweight gun fitted to the four F125 frigates. During acceptance firing off Andøya, Norway, in 2022, the frigate Rheinland-Pfalz fired several guided projectiles at a target area approximately 30 kilometres away. According to the Bundeswehr, the rounds landed within a few metres of one another near the designated aim point, validating ammunition handling, programming, firing and precision under operational conditions. The German procurement process was then expected to run through the end of 2026. This experience reduces risk in the projectile, guidance unit and German logistics chain, but it does not qualify Vulcano for the Mk 45. The BAE gun has a different loading system, chamber geometry, ammunition interface and fire-control architecture. A new qualification campaign must therefore address projectile dimensions, propelling charges, pressure curves, recoil loads, automatic handling, fuze and guidance programming, barrel wear, software interfaces and safe operation across the gun’s elevation and training limits.

If that work succeeds, the combination would give Mk 45 users a guided land-attack option with roughly three times the published range of conventional U.S. Navy ammunition. At 80 kilometres, a frigate could strike coastal observation posts, radar sites, command facilities, ammunition points or vehicles without approaching the shoreline as closely as it would for standard naval gunfire. Semi-active laser guidance would permit terminal correction against a designated moving or relocatable target, provided that an aircraft, unmanned aerial vehicle, ground observer or special-operations team maintains laser designation. Far-infrared guidance could reduce dependence on continuous external illumination but would require reliable target discrimination in cluttered coastal environments. The ammunition would not replace an anti-ship or land-attack missile: its smaller warhead limits effects against hardened structures and large warships. Its value is instead in providing more numerous, lower-yield precision engagements and retaining expensive missiles for targets requiring greater range, penetration or destructive effect.

The IRIS-T portion is less mature and contains more unanswered engineering questions. Diehl’s current family includes the short-range IRIS-T SLS, using the standard air-to-air missile with an imaging-infrared seeker, datalink and thrust-vector control, and the larger IRIS-T SLM interceptor. Diehl gives the latest SLS configuration a 12-kilometre engagement range and 6-kilometre altitude coverage, while current SLM material states a range of up to 60 kilometres and an altitude of 20 kilometres. Those land-based figures cannot simply be transferred to a ship. Naval integration requires a sealed launch canister, corrosion protection, electromagnetic-compatibility testing, shock and vibration qualification, safe exhaust management, launcher-control software and connection to the ship’s surveillance radar and combat-management system. BAE Systems produces the below-deck Mk 41 Vertical Launching System and the fixed-angle Adaptable Deck Launching System, but the memorandum does not state that either has been selected. The Adaptable Deck Launching System is compatible with Mk 41-type canisters and has launched an Evolved SeaSparrow Missile during testing, making it a technically relevant option rather than a confirmed solution.

The collaboration is therefore best understood as an effort to create two qualified weapon combinations that neither company can offer independently. BAE Systems gains access to a European guided 127 mm round already entering German service and a missile family used or ordered by 21 countries. Diehl gains access to an installed base of more than 240 Mk 45 shipboard applications and to BAE launcher and canister engineering. For Germany, the arrangement could create an alternative to the existing Leonardo gun-and-ammunition combination and increase competition in future naval procurement, but the companies have not linked it to the F127 air-defence frigate or the planned MEKO A-200 DEU acquisition. The decisive issue will be whether the companies fund full qualification and secure a launch customer. Until then, the memorandum defines an engineering and market-access strategy, not an operational capability.

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