14 April 2024

US Navy Completes First MK 38 MOD 4 GWS Install

Richard Scott 

The twin-mount MK 38 MOD 4 fit – comprising the MK 88 MOD 4 gun mount together with the MK 48 MOD 2 electro-optical sight system (EOSS) and the MK 134 MOD 0 operator console – was installed on the ship during a recent depot maintenance and modernisation period in San Diego. Mustin is now planned to run an at-sea Quick Reaction Assessment with the MK 38 MOD 4 system.

The US Navy is procuring the MK 38 MOD 4 GWS to address deficiencies in current counter-unmanned aerial system (C-UAS) and counter-unmanned surface vessel (C-USV) capabilities, with the aim being to initially field the system on all DDG 51 Flight IIA and Flight III destroyers. According to the service, the MK 38 MOD 4 GWS is designed to bring greater accuracy, lethality, and effective range for C-UAS and C-USV applications through the integration of fire control, the Northrop Grumman MK 44 Bushmaster II 30mm gun, the EOSS sensor suite, and the AEGIS combat system.


MSI-Defence Systems’ Seahawk DS30M A2 dual-feed single 30 mm mounting provides the basis for the GWS 88 MOD 4 gun mount. Specific adaptations for the US Navy include the integration of a co-axial 0.50-cal M2HB heavy machine gun and a revised power system architecture.

The associated MK 48 MOD 2 EOSS is installed off-mount. The fully stabilised, dual-axis EOSS director contains both TV and thermal cameras, and a high refresh rate laser rangefinder.


MSI-Defence Systems has supplied an initial eight prototype MK 38 MOD 4 systems to support test and qualification activities. A MK 38 MOD 4 live fire event performed by the Naval Surface Warfare Center Dahlgren Division in July 2022 on the Potomac River Test Range provided an end-to-end demonstration of the full weapon system, including detection, tracking and engaging live surface and air targets with live ammunition against static and dynamic targets.

First low-rate initial production contracts for the MK 38 MOD 4 GWS were awarded in September last year. A US$23.5 million contract placed by the NSWC Indian Head Division funded MSI-Defence Systems US LLC (MSI-Defence Systems’ US subsidiary in Rock Hill, South Carolina) for the procurement of 15 MK 88 MOD 4 gun mountings plus associated hardware and spares. A second award – an indefinite-delivery/indefinite-quantity contract from the NSWC Crane Division valued at US$29.3 million – covered the procurement of the MK 48 MOD 2 EOSS plus spares, repairs, and transportation cases.

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