BAE Systems Bofors’ (Hall A, Stand AP301) latest 40mm Mk 4 naval gun is being displayed as part of a Saab turnkey combat system proposed for PT Lundin’s stealth trimaran fast attack craft.
Private venture development of the 40mm Mk 4 mounting – the latest evolution of the Bofors 40mm L/70 line – began in 2009, with the aim of providing small inshore patrol craft and offshore patrol vessels with a compact, lightweight and affordable multirole weapon system. BAE Systems began land-based firing trials of its 40mm Mk 4 prototype in 2011, and has subsequently undertaken at-sea firing trials on the patrol craft Jägaren. First production orders are expected shortly.
The system has been designed to realise a 40 per cent reduction in weight, volume and price compared with the 40mm Mk 3; BAE Systems believes that this lower price point and reduced installation footprint will open up opportunities in the patrol craft market previously denied to heavier 40mm turrets.
Although evolved from the Mk 3, the new 40mm Mk 4 mounting has been re-engineered so as to bring weight down to less than 2,300kg without ammunition. To achieve this, a new elevating mass (brought across from the Swedish Army’s CV 90 armoured vehicle family) is introduced, electric drives are used in place of hybrid electrohydraulics, the cupola is more compact, and a fully digitised modular system architecture is adopted.
The primary magazine holds 30 rounds. An intermediate magazine holds an additional 70 rounds, giving an on-mount capacity of 100 rounds. Loading of ammunition from the intermediate magazine to the primary magazine is fully automatic, while the intermediate magazine can be reloaded from below deck.
Although the 40mm Mk 4 can fire any 40mm L/70 ammunition, BAE Systems promotes full compatibility with its latest programmable 3P ammunition on the grounds of improved flexibility, optimised effects, and reduced logistics overheads.
3P ammunition can be programmed in any one of six different modes for different target threats: gated proximity for air defence; gated proximity mode with impact priority (air defence large targets); time mode (against small, fast and manoeuvring surface targets and concealed onshore targets); impact mode for engaging surface targets; armour-piercing mode against armoured surface targets; and proximity in the default mode.
The 40mm Mk 4 gun has a maximum range of 12.5km, and a cyclic rate of fire of up to 300 rounds a minute. Rather than being limited to single shot or fully automatic, the operator can now select any firing rate between 30rds/min and 300rds/min.
The 40mm Mk 4 has been baselined by Saab and PT Lundin as the main gun armament for the latter’s 63m stealth fast attack trimaran.
For this particular application, the weapon cupola would be shaped to match the faceted topside structure of the vessel itself, so maintaining the vessel’s low radar signature.