THE RENAISSANCE OF NAVAL MEDIUM CALIBRE

BY LUCA PERUZZI

The appearance of a wider range of more lethal weapon systems on the sea, from more capable sea-skimming missiles to challenging aerial threats, such as drones and loitering munitions, have pushed both main and smaller naval forces towards the acquisition of multi-purpose gunnery weapon systems with longer range and higher accuracy, capable to fire both conventional and programmable ammunitions, the latter reducing the number of rounds for each engagement and enhancing the killing probability. The European industry is leading the market of medium calibres from 40 to 76 mm, which is registering a wider use of multi-purpose gun mounts as main armament for both first and second line combatant and patrol vessels. These are equipped with guided and programmable ammunitions to deal with a wider range of aerial threats and longer range guided and unguided rounds to support surface warfare operations in the littoral environment.

Bae Systems Bofors 40 Mk 4

In December 2022, the Brazilian Navy has commissioned the first of the Macaé-class patrol ships equipped with the 40 mm BAE Systems Bofors 40 Mk 4 naval gun system. In addition to Brazil, the new gun has been contracted or is in service with four additional customers, including Finland on board its Hamina-class upgraded missile boats; Belgium and the Netherlands on mine countermeasures mother vessels for unmanned vehicles being built by Kership shipbuilding jointventure under the jointly-managed Naval GroupECA Group remotely operated MCM package programme; and the UK on board the new five Type 31 multirole frigates under construction by Babcock International. With a significantly re-engineered gun mount introducing a more compact and stealthier cupola, the same elevation mass of Swedish Army’s CV 90 armoured vehicle, and new electric drives instead of older hybrid electro-hydraulics, alongside a fully digitised modular architecture, the Mk 4 gun has an unlimited training thanks to slip ring and an elevation of -20°/+80°. It has a variable rate of fire up to 300 rpm. Muzzle velocity is 1,012 m/s, while maximum range is 12.5 km. With a gun mount weight of 2,300 kg excluding ammunition compared to the 3,700 kg of the Mk 3 version, and a height of less than 2 meters, the new model has a 30 ready-to-fire rounds in the primary magazine, plus 70 rounds in an intermediate magazine that can automatically reload the previous one, with the possibility to shift between two different ammunition types during the firing. Capable to employ any 40mm L/70 round, the latest Bofors 40 version offers full compatibility with ‘smart’ 3P programmable ammunition. Programmed at

Capable to employ any 40mm L/70 round, the BAE Systems Bofors 40 Mk 4 offers full compatibility with latest ‘smart’ 3P programmable ammunition.

© BAE Systems

the point of firing according to the threat type and engagement scenarios, and also used in the 57 mm calibre, the 3P ammunition can be set in any one of the six different modes so as to optimise effect: gate proximity for air defence; gate proximity with impact priority (air defence against large targets); time (against small, fast, and manoeuvring surface targets and concealed onshore targets); impact for engaging surface targets; armour-piercing against armoured surface targets, and proximity in the default mode.

Leonardo Marlin 40

With an extensive experience in manufacturing 40 mm naval guns, with more than 850 systems of different families in service with 30 navies worldwide, Leonardo is currently promoting the latest addition, the Marlin 40 (previously known as Forty Light), which has already gained international success. Leonardo acknowledges the supply to the Indonesian Navy to equip so far four PC60 patrol boats and the two Teluk Bintuni-class LSTs, while EDR Magazine understood from shipyards renderings and other sources that the Marlin 40 was also selected by the Nigerian Navy to equip the Dearsan-built two 76 meters OPVs, and by the Pakistan Navy’s for its two 98 meters Damen OPV 2600 platforms. Re-using much of the in-house 40 mm well-proven technology in terms of the 300 rpm 40/L70 gun already used in the Fast Forty single gun and ammunition feed, while adapting mechanical structures, electrical servos, electronics and software from the latest generation Marlin 30 mm gun mount, Leonardo developed an ITAR-free 40 mm naval gun weighing no more than 2,100 kg without ammunition in a full remote configuration or ILOS (Independent Line of Sight). It comes also

Capable to employ any 40mm L/70 round, the BAE Systems Bofors 40 Mk 4 offers full compatibility with latest ‘smart’ 3P programmable ammunition which effect can be optimised according to the threat type and engagement scenario. © BAE Systems with a reduced footprint and no deck penetration to make it installable on a wide variety of vessels. As option, the Marlin 40 may be equipped with an integrated hoist to enable ammunition loading from covered position below deck. The Marlin 40 is equipped with a recoil-actuated gun with a single shot, 100 rpm and 300 rpm rate-of-fire and an up to 80 ready-to-fire rounds (adding 175 kg to the overall mass) magazine with a dual gun feed to allow switching between programmable and all types of 40 mm conventional ammunition. With a maximum effective range of 4,500 meters, the Marlin 40 is equipped with a slip ring allowing a 360° training range which can be limited with mechanical stops and obstacle contouring data and no-firing zones settable via software. Featuring a full digital architecture and powerful electrical servos, the gun has a training speed and acceleration of respectively 120°/s and 200°/s2 and an elevation range of -20/+85° with a speed and acceleration on the same plan of respectively 75°/s and 200°/ s2. The elevating mass with automatic dual feed system and magazine are all enclosed within a low RCS gun carbon fibre-made shield turret with limited footprint (2,240 mm wide and 2,003 mm high without the independent electro-optical director with a 4,234 mm length including the barrel) and hatches on the turret sides for easy access and maintenance. The 80-round magazine is part of the elevating mass, a hatch in the upper part allowing easy ammunition reloading. The Marlin 40 mm gun comes in two different configurations: one is remotely controlled by the CMS and the ILOS, and can operate in autonomous mode through its own local control console with ballistic processing, while the second operates stand-alone using the electrooptical director (EOD) mounted above the gun. Capable to operate independently from the gun line of fire for panoramic and target surveillance, the advanced EOD is equipped with a highly accurate sensor suite (with an automatic tracking mode) consisting of daylight and IR cameras providing a detection, recognition and identification ranges of respectively 20/9/4.5 and 15/6.8/3.5 km with respect to a NATO standard target, while the laser range finder reaches 6.5 km.

NAVAL GROUP/THALES RAPIDFIRE

During the Euronaval 2022 exhibition, the temporary consortium formed by Thales and Nexter unveiled the real size mock-up of the RAPIDFire, ‘an effective close-in defence capability against modern air and surface threats’, developed under contract with the French General Armaments Directorate (DGA) in a naval version to equip future and present French Navy platforms. The RAPIDFire is under production and is being installed for at-sea firing tests and qualification on the Jacques Chevallier, the first of the four Bâtiments Ravitailleurs de Forces (BRF) or fleet replenishment vessels. It will then also be installed on other naval units, among which the future Patrouilleurs Océaniques (PO). Centred on an over-deck self-contained gyro-stabilized gun mount, the RAPIDFire is equipped with the 40 CTA (40 mm Cased Telescoped Ammunition) gun developed by the CTAI joint-venture between Nexter and BAE Systems. It is in series production and in service with the French Army and soon with the Belgian Army, installed in the T40 two-man turret fitted onto the Jaguar 6x6 reconnaissance armoured vehicle, and was delivered to the UK MoD for the British Army Ajax tracked vehicle. The RAPIDFire features an automatic ammunition management system with a 140 ready-to-fire rounds magazine, advanced algorithms for fire control functions, and a co-located but independent gyro-stabilized optronic director. Equipped with the same peculiar ammunition design, in which the projectile is embedded in the tubular case, hence the “cased telescoped” name of the weapon, the side-loading system permits to shift from one type of ammunition to another, the link-less single feed system and rotating chamber- based loading/expulsion system ensuring short fire cycle and reduced jamming. Developed to operate in the maritime environment and aimed primarily at air targets including small drones and anti-ship cruise missiles alongside small surface targets, the RAPIDFire gun employs the full 40 mm CTA family of rounds, including the under development anti aerial airburst round (A3B) as it is known in France, while internationally it is named KEAB (Kinetic Energy Air Burst). The latter releases a payload of 660 grams of tungsten pellets that forms a cloud of subprojectiles in front of the target, specifically shaped to cause maximum damage to air targets. However, due to the heavier weight of the latter ammunition and the need to apply a comparable impulse during the firing, the thickness and therefore weight of the

The Marlin 40 mm gun comes in two configurations: one remotely controlled by the CMS and the ILOS, that can operate in autonomous mode through its own local control console, while the second operates in stand-alone mode using the independent electro-optical director mounted above the gun mount. © Leonardo gun barrel has been increased and a new muzzle brake with three baffles, compared to the two of the Jaguar cannon, was introduced. The under development A3B will have an engagement range against mentioned targets up to 4,000 meters.

The over-deck, self-contained with inclined sides turret, which can be installed on ships beyond 30 meters length, has a weight of 3.5 tonnes with ammunition. It has an overall elevation arc of 85°, maximum elevation depending on the depression required by the customer. The newly developed and dedicated gyro-stabilized optronic director provided by Thales and featuring medium wave IR and daylight channels and a laser range finder can be used not only for targets search, acquisition, identification, classification and engagement but also for panoramic surveillance. The RAPIDFire has growth capabilities, being capable to accommodate guided propelled rockets as well as a tracking radar as unveiled on the future French Navy’s aircraft carrier model showed at Euronaval, among other enhancements.

Bae Systems Bofors 57 Mk 3

In December 2022, BAE Systems has signed two contracts worth approximately $32 million in a combined procurement for its Bofors 57 mm 3P (Prefragmented, Programmable, Proximity-fused) advanced ammunition in a combined procurement from both the Swedish Defence Materiel Administration (FMV) and the Finnish Defence Forces Logistics Command for their Bofors 57 Mk 3 naval gun systems. Developed from the beginning to capitalize on the multi-target functionality provided by the ‘smart’ 3P ammunition, the Bofors 57 Mk 3 is the third generation of a family’s lineage of high rate-of-fire multipurpose weapon system with a compact lightweight mounting, which can be installed from smaller surface combatants (down to 150 tons) to large platforms, to provide an anti-air, anti-surface and shore bombardment capability. Developed and produced at BAE Systems Bofors in Karlskoga, Sweden, the worldwide club of customers for Bofors 57 Mk 3 and its US version Mk 110 (assembled in the US) has expanded in the latest years, today including the navies and coast guards of Brunei, Canada (as upgrade), Finland, Germany, Indonesia, Mexico, Malaysia, Saudi Arabia, Sweden, UAE, UK and US. Equipped with a fully automatic, computerized ammunition handling system capable to accommodate 120 ready-to-fire rounds in the gun mount with a loading system from the magazine centred on two parallel hoists enabling instant switching between ammo types, the Bofors 57 mm gun has a -10°/+77° elevation range, a maximum rate of fire of 220 rpm and a maximum range of 17 km. An integrated muzzle-velocity radar is fitted to supply data to the fire-control computer for calculating ballistics and target intercept point, enabling the gun to achieve maximum accuracy and fully exploit 3P functionality. It is managed by a single remote operator console but, as a backup, it can also be controlled from a PC-based gun controller located anywhere onboard thanks to a gun-mounted TV-camera. Total system weight, excluding ammunition, is 7,000 kg. In addition to the 3P ammunition (designated Mk 295 Mod 0 in the US) which can be programmed in six different function modes, allowing the engagement of a wide range of targets, from drones to missiles, from swarming boats to surface vessels, the US DoD is procuring the L3 Mustang Technologies

Mk 332 Mod 0 High Explosive-4 Bolt Guided (HE-4G) cartridge under the ALaMO (Advanced Low-cost Munitions Ordnance) programme, and is developing a next generation munition under the Defense Advanced Research Projects Agency (DARPA) MultiAzimuth Defense - Fast Intercept Round Engagement System

The worldwide club of customers for BAE Systems Bofors 57 Mk 3 and its US version Mk 110 (assembled in the US) has expanded in the latest years, today including

BAE Systems has recently signed two contracts worth approximately $32 million for its Bofors 57 mm 3P (Prefragmented, Programmable, Proximityfused) advanced ammunition in a combined procurement from Sweden and Denmark.

© BAE Systems

(MAD-FIRES) programme. The HE-4G is a hit-tokill ammunition with a fragmenting incendiary warhead that allows countering swarms of unmanned surface vehicles before these come within their effective weapon range. The MADFIRES programme is focused on development and test of technologies and a prototype design of a gun hardened projectile, capable to defeat a raid of fast, maneuvering anti-ship cruise missiles. It consists of a gun, a smart round, an illuminator and a mission computer, the technologies critical to the projectile performances including a gun hardened shell and a novel Ka-band seeker. The system is under development by Raytheon Missiles and Defense and sized to be fired by the 57 mm gun as a new ship self-defense system. According to DARPA FY 23 budget documentation, the current phase of the programme is focused on demonstrating endto-end system performances against surrogate supersonic targets. Increased funding for FY 23 reflects activities leading up to sea testing of a fully integrated demonstrator.

Leonardo Super Rapido And Single Deck

The OTO 76/62 mm Super Rapido gun mount (SRGM) developed by Leonardo is enjoying a new life and is acquiring new customers thanks to its digitization, the development of new long-range guided and unguided ammunitions in addition to the widening market for the Strales configuration, and the entering into service of the new generation 76 Single Deck version. With a 120 round per minute (rpm) rate-of-fire, limited on-board footprint and weight (7,900 kg mass without ammunition which reaches 9,200 kg with the Strales guidance kit), the SRGM is currently offered with a multifeed (hence the 76/62 mm SR MF designation) ammunition magazine based on two distinct chutes, each hosting up to 38 rounds, and a rapid reloading system with two ammunition handlers capable to work even during the firing action and to select any ammunition contained in the two branches regardless of its position. It also features a new AC3v2 remote digital console, a digital link to fire control systems (FCSs), as well as a new universal ammunition programmer for both unguided and guided rounds. In the Strales configuration that Leonardo offers for both new production and in-service (via an upgrade kit) guns, the SRGM comes with an RF Ka-band antenna guidance kit installed on the mount and the DART (Driven Ammunition with Reduced Time of Flight) guided rounds. Developed to cope with anti-ship missiles and asymmetric threats and exploiting the DART’s high-speed round (1,100 m/s muzzle velocity) and its manoeuvring capabilities, the SRGM in this configuration has an engagement range of 6-8 km and is also capable to deal with both high-subsonic and the more demanding supersonic threats. No live trials have however so far been conducted against the latter threat, confirmed Leonardo. The company is already delivering to customers BER (Ballistic Extended Range) rounds with a 27 km range and is developing the 76 mm Vulcano sub-calibre guided long-range round equipped with IMU and GPS for autonomous guidance and capable of ranges up to 40 km. Under contract with the Italian Navy as launch customer, deliveries of 76 mm Vulcano production rounds are expected in 2023-2024. The Italian MoD’s Naval Armaments Directorate recently awarded Leonardo a multiple batches supply contract for DART ammunitions to boost their inventory in order to equip the widened number of Strales-equipped platforms (so far FREMMs, PPAs, the Cavour aircraft carrier, Horizon destroyers, and the Trieste LHD). In the last years, the SRGM was procured or selected by the Navies of Qatar, Israel, Greece, Senegal, Bulgaria, Turkmenistan, Indonesia, Pakistan, Poland and, according to media, Ukraine. The SRGM in the Strales configuration was sold to Colombia and Egypt, while EDR Magazine also understood it was acquired by the UAE. The Indian company BHEL, as the local licensee for the gun manufacturing, received an order from the Indian MoD for the SRGM with upgraded capabilities to be installed on most Indian Navy platforms, which EDR Magazine identified as the Strales/DART and 76 Vulcano. The Taiwan MoD plans to equip the Navy’s fleet with the Strales configuration, according to local media. Other customers are interested in coupling the SRGM/ DART with the new Leonardo dual-band radarEO/IR NA-30S or the Thales Nederland Pharos. The latter union (no details were added among the traditional SRGM or the Single Deck version choice) was selected by the Netherlands MoD together with the Raytheon RAM missile system to replace the in-service Goalkeeper close-in weapon system and equip the new multi-purpose frigates to be jointly procured by the Netherlands and Belgium.

A completely new lighter and lower footprint version of the SRGM developed under contract by the Italian Navy, the 76 Single Deck, features a new gun mount architecture with almost 40% weight reduction, while maintaining the same gun rate of fire with an air-cooled gun barrel, ready-to-fire ammunitions and the Vulcano and DART-guided ammunition firing capability, the latter through a Ka-band RF guidance antenna enclosed under the gun in a stealthy turret. The 76 Single Deck is operational on board Italian Navy Thaon di Revel-class PPAs since 2022.

MKE 76/62 MM AND THE TURKISH NATIONAL NAVAL GUN PROJECT

In late August 2022, the Turkish MoD announced that the Istanbul Shipyard Command and the state-owned Ankara-based MKE (Makine ve Kimya Endüstrisi A.Ş., Machinery and Chemical Industry Inc.) company active in the artillery, small arms and ammunition business, successfully completed the harbour and sea acceptance trials of the indigenous 76/62 mm naval gun. The National Naval Gun Project was conceived to develop a national product in order to relief the Turkish Navy from dependency of foreign manufacturers and their potential export limitations. It is intended to substitute the Oto Melara 76/62 mm Compatto in the Turkish Navy inventory and provide a new product for the international market. With a digital architecture in terms of fire and automation, the MKE 76/62 mm gun system is characterized by a reduced radar cross section shield and a deck penetrating ammunition magazine. It features a weight of less than 7,500 kg without ammunition, which reaches 8,500 kg with the ammunition payload of up to 80 rounds. With a sea or fresh water barrel cooling system, the 76/62 mm gun has a maximum rate of fire of 80 rpm and can reach a range of 16 km, which increases to 20 km when using extended range rounds. Activities are reported being carried out also on notspecified ‘smart’ rounds. Equipped with a slip ring it can continuously rotate in azimuth, training speed declared being of 60-65°/s, with an acceleration of 72°/s2. Capable to engage both surface and air targets, the MKE 76 mm has an elevation arc of –15°/+85°, with an elevation speed of 35-40 °/s and an acceleration of 72°/s2. Following the completion of land-based tests and qualification, the first single-round firing was achieved in November 2021, the gun mount was installed and integrated on board the Beykoz corvette in July 2022 and the following month conducted the first live trials campaign, completing land bombardment, surface and anti-air firings within the scope of harbour and acceptance tests, successfully passing them according to the Turkish MoD.