Land Vehicles - DEFENCE MANAGEMENT JOURNAL, Issue 40
The WFLIP dilemma
There are four remaining competitors for the contract to supply a new gun armament, initially for the British Army's FV510 Warrior MICV (Mechanised Infantry Combat Vehicle). Three of them are similar in that they have based their proposals around the American ATK MK44 30/40mm gun: Selex Sensors and Airborne Systems is offering the HITFIST 30 two-man turret from its sister company Oto Melara, both subsidiaries of the Italian Finmeccanica group; Lockheed Martin Insys offers a turret based on the existing Warrior design, adapted by the German company Rheinmetall Landsysteme; and General Dynamics has its MK46 turret as developed for the USMC's amphibious EFV (expeditionary fighting vehicle). The fourth is very different – the 40mm CTWS (cased telescoped weapon system) from CTA International, an Anglo-French joint project between BAE Systems and Nexter.
All of these are designed to deliver a number of urgent improvements on the Warrior's existing Rarden L21A2 30mm armament. These include an advanced sensor, fire control and defensive aids suite, plus a fully powered and stabilised gun mounting so that the vehicle can fire on the move rather than having to stop to take aim, as at present. In addition, the new gun will have a continuous ammunition feed, instead of three-round clips, which have to be manually loaded by the commander (distracting him from his primary task). Finally, they will all offer the latest development for such weapons: a high explosive air burst (HEAB) capability.
The aim of HEAB is to defeat enemy troops hiding behind cover by arranging for HE fragmentation shells to detonate directly overhead, a capability that has been calculated to greatly increase the effectiveness of anti-personnel fire. To achieve this is no simple matter, however. The installation requires a fire control system that will precisely measure the distance to the target, calculate the time of flight of the shell, and electronically set a time fuse in the shell (either when the round is loaded into the chamber or as the shell leaves the gun muzzle) to detonate it at the correct instant. The precision required of the fusing system means that HEAB ammunition is considerably more expensive than conventional HE shells, which are exploded by point-detonating impact fuses. The HEAB shells do of course also have a point-detonating fuse for when this mode is required.
HEAB is alternatively known as ABM – air burst munition – although this term is also used to refer to a rival approach based on Rheinmetall's AHEAD (Advanced Hit Efficiency And Destruction) 35mm anti-aircraft and missile round. This consists of a shell filled with tungsten pellets with a small burster charge, which is timed in the same way as HEAB, but to detonate several metres in front of the target, sending an expanding cone of pellets forwards. Special anti-personnel versions have been developed in both 30mm and 35mm calibres. Compared with HEAB, they have the benefit of concentrating more pellets in the target area, but they lack HEAB's ability to distribute fragments directly downwards from, and even behind, the bursting point in order to catch troops hiding behind walls and other cover.
The guns
The MK44, known in its original version as the Bushmaster II, is one of ATK's power-driven Chain Gun family, in effect a scaled-up version of the 25mm M242 Bushmaster used by the US Army's M2 Bradley and Stryker LAFVs (light armoured fighting vehicles), as well as in many other army and naval applications. The belt-fed MK44 is chambered for the 30x173 cartridge originally developed for the A-10 attack plane's formidable seven-barrel GAU-8/A 'tankbuster' cannon. The same cartridge is also used in the Mauser MK 30 family, rivals to the MK44 and selected for the new German Puma MICV.
ATK refer to the MK44 as a '30/40mm' gun because a version of the 30x173 cartridge with the neck diameter increased to 40mm calibre, the 'Super 40', or S40, is being developed. It originated in the ALACV (Advanced Light Combat Vehicle Armament) project initiated by the US Army's Armament Research, Development and Engineering Center (ARDEC), under a contract lasting between FY 2000 and 2003. General Dynamics Ordnance and Tactical Systems (who had primary responsibility for the cartridge design) has continued to work on the project since the end of the contract. The primary purpose of the S40 is to increase the HEAB shell weight to improve its effectiveness, although APFSDS performance is also expected to be enhanced. It is intended that existing 30mm versions of the MK44 could, in the future, be converted to S40 calibre by changing the barrel and making other amendments.
The 40mm CTSW, known for short as the CT40, is the product of a long development cycle starting in the 1990s, during which many details of the gun and ammunition have changed. It uses unique cartridges that are 'telescoped', ie. have the projectiles completely buried within the case, resulting in a cylindrical cartridge. This enables it to utilise a loading system in which the gun's chamber is not a part of the barrel, but a separate unit that is pivoted to face the side for loading. Each new round pushes out the fired case, after which the chamber is rotated to line up with the barrel for firing. This results in a very compact mechanism and ammunition feed, a very important characteristic for an LAFV gun, especially for a turret that has to be compatible with the Warrior's small turret ring. In the interests of simplicity, the ammunition feed is arranged on the trunnion axis of the gun, which means that the location of the chamber does not change with the gun's elevation, unlike belt-fed guns in which room has to be made for the belt feed to move as the gun is elevated.
The CT40 was originally intended to be fitted to the abortive US/UK TRACER joint project for a tracked reconnaissance vehicle (a role that will now be filled by FRES Recce – the Future Rapid Effects System reconnaissance variant). For the WFLIP project, the MOD decided to invite competitive bids, initially specifying a gun of at least 35mm calibre with AP ammunition able to penetrate the frontal armour of the current Russian BMP-3 MICV out to 2,000m. It seems that the requirements have since been softened, first to allow the 30mm proposals to compete on the grounds that a future upgrade to 40mm was possible, and more recently to reduce the specified penetration.
Ammunition performance comparison
Both the MK44 and the CT40 offer similar capabilities, the key differences lying in the performance of the ammunition. So how do the 30mm, S40 and CT40 rounds compare?
The 30x173 is in fact very close in appearance, size and performance to the 30x170 round, which has been used by the Rarden cannon for over three decades (although the two are not interchangeable). The muzzle energy developed by both cartridges is in the region of 200-220kJ. HE blast effect and APFSDS (armour piercing, fin stabilised, discarding sabot) penetration will therefore be closely comparable, the 30x173's only significant advantage being in the availability of HEAB/ABM ammunition (APFSDS ammunition was recently cleared for use in the Rarden, after a very protracted programme). The MK310 Mod 0 PABM (HEAB) shell for the MK44 weighs in at 423g, while the APFSDS flight projectile (minus the sabot) weighs about 160g and is fired at 1,385m/s (giving an effective flight energy of 153kJ).
The S40 fires a HEAB shell, which weighed 680g for the ALACV trials, although it was planned to raise this to 725g. In either case, muzzle energy was 340kJ. The APFSDS flight projectile weighed in at 230g, with an ALACV velocity of 1,350m/s, although it was hoped to raise this to 1,450m/s later, giving effective energies of 210 to 242kJ.
The CT40 fires a GPR-T (HEAB) shell of 1,000g, developing a muzzle energy of 500kJ. The APFSDS flight projectile weighs 320g and is fired at 1,480m/s, developing 350kJ.
To sum up, there are clear performance steps with these three rounds, the 30x173 being outclassed by the S40, which is, in turn, significantly outperformed by the CT40. The HEAB shell weight gives a good indicator of the effectiveness of the ammunition in the airburst role, while the APFSDS flight energy acts as a proxy for armour penetration performance. Using these measures, the S40 offers advantages of 37-60% over the 30x173, while the CT40 provides further performance gains of 38-67% over the S40.
The current status of the competitors
The contenders are not all at the same stage of readiness. The CT40 is the most advanced, having progressed to the live-crew firing stage last year. CTAI are now offering a modified turret design (MTIP2), first revealed at DSEi last September and test-fired in that month. The ATK MK44 cannon is fully developed and in service, but the WFLIP installations are not. Lockheed Martin Insys test-fired their first turret design towards the end of last year, but then only a few shots of training ammunition were fired by remote control. Furthermore, they are planning to replace this with a second turret design, which will be fully compliant with the requirements, not due for unveiling until March 2008. Selex's HITFIST turret is established, but again the 30mm WFLIP installation is not. The GD MK46 turret has reportedly experienced significant difficulties (mainly to do with the ammunition feed) in trials of the troubled EFV project. Finally, the Super 40 version of the MK44 gun and its ammunition are a long way behind the others, still being at the developmental stage.
What's happening elsewhere?
While the performance order of merit of the three contenders is very clear, this needs to be put into context by looking at the decisions for future armament that other armies are taking. The US Army will probably move from 25mm to 30mm calibre at some point, while the Russians seem likely to keep their existing 30mm guns for the time being, although they have introduced a new turret with a powerful 57mm automatic gun for re-arming some LAFVs. In both armies, however, it can be argued that pressure to move beyond the performance of the 30mm gun in MICVs is reduced by other factors: in the case of the USA because there is such a wide variety of other land and airborne systems available for dealing with tougher targets, and the Russians because their BMP-3 MICV mounts a formidable 100mm gun alongside the 30mm.
In smaller armies, the 30mm calibre has become the new baseline, being the most popular choice for fitting to new LAFV projects, both wheeled and tracked. Several countries have, however, decided that 30mm is inadequately powerful. Sweden has mounted the formidable, but huge, 40/70 Bofors gun to its CV90 for many years, and the new South Korean Infantry Fighting Vehicle is taking a similar route. Japan chose the 35mm Oerlikon KDE for its Type 89 MICV several years ago, and both Denmark and the Netherlands have recently adopted the Bushmaster III, firing the same 35x228 Oerlikon cartridge (developing c.400kJ muzzle energy – more powerful than the Super 40), for their CV9035 purchases. The German Army wanted to adopt a 35/50mm Rheinmetall Rh 503 gun for the new Puma MICV, but this is a long way from production-ready and they were forced to accept the 30mm Mauser MK 30-2 for financial reasons, a rather small gun for such a massive vehicle.
Conclusions
There is clear evidence of a classic gun/ armour race developing among LAFVs. The new generation of vehicles is showing substantial weight increases over older designs (and existing vehicles have had their weight considerably increased), mainly because extra protection is felt to be necessary. This is making the job of the LAFV gun in penetrating these vehicles that much harder. It is significant that one of the reasons given by the Dutch for selecting a 35mm rather than a 30mm gun was an assessment that the performance of the 30mm APFSDS was inadequate against the latest uparmoured versions of the BMP-3, the Russian equivalent to the Warrior.
The arguments given against more powerful ammunition of larger calibre are its cost, plus the reduction in the quantity that can be carried. In both cases, there are counter-arguments: for HEAB ammunition, that a larger number of 30mm rounds will need to be fired to achieve the same effect (probably three times as many 30mm compared with the CT40); and for armour-piercing rounds, that to employ ammunition that cannot satisfactorily deal with the current (let alone future) top-line opposition is a false economy, a particular concern with FRES Recce, whose armament is primarily intended to knock out its opposite numbers.
The WFLIP decision will be crucial for more than just the future effectiveness of the Warrior; it may also determine the future of the CTAI project, and thereby affect the choice of LAFV cannon for the British FRES Recce, plus future French LAFVs and potentially other armies.
Anthony G Williams is a military technology consultant and author, specialising in small to medium calibre ammunition and weapons. He is Co-editor of Jane's Ammunition Handbook, and maintains a website at http://www.quarry.nildram.co.uk.