Light AFV guns and the WCSP and FRES Scout projects
© Anthony G Williams
Based on a presentation given to the 21st Small Arms and Cannon Symposium held at the Defence Academy of the United Kingdom, August 2007
UPDATED 5 MAY 2013
The cannon mounted in the turrets of LAFVs (Light Armoured Fighting Vehicles) have two principal uses: one is to engage their equivalents, for which they need guns powerful enough to penetrate their armour when using AP ammunition, while the other is to engage softer targets; unarmoured vehicles, buildings and other cover, and troops.
A gun-armour race has been slowly developing among LAFVs. The previously common 20mm calibre, particularly the 20x139 used in the Rheinmetall Rh 202 among others, has mainly been superseded for this purpose by the 25x137 NATO round, principally in the ATK M242 Bushmaster Chain Gun, but the 30mm calibre is now standard for almost all new developments. The British 30mm Rarden L21A2 gun (30x170) has of course been in service for decades, as have the Russian BMP 30mm guns (30x165), and these have more recently been joined in service by the Mauser MK 30 and the ATK Bushmaster II (since replaced in production by the marinised MK44 version developed for the USMC's EFV), both in 30x173 calibre. One oddity is the 1950s Soviet 30x210B cartridge, developed for the NN-30 naval gun, which was adopted by Yugoslavia in the 1980s for the Zastava M86 (single ammo feed) and M89 (double feed) AFV guns; this has been revived for new Serbian LAFV developments.
M2A2 Bradley with 25mm M242 Bushmaster
Moving up in power, the 35x228 Oerlikon round as used in the Oerlikon KDE has been in service for some years in the Japanese Type 89 MICV. The Netherlands and Denmark have also chosen this round for their new CV9035 MICV, only this time in ATK's Bushmaster III. The 40x365R Bofors L70 has been in Swedish service for some years in the CV9040, and the round is also used by the new Korean Infantry Fighting Vehicle. In the late 1970s, Germany considered the idea of a Marder MICV armed with a version of the Bofors 57mm in 57x438R calibre, but this went nowhere.
A few years later Otobreda of Italy and IMI of Israel co-developed the self-loading 60mm HVMS 60 (High-Velocity Medium-Support) around new 60x410R ammunition. After a while, the two firms parted company and continued separate developments of the gun and ammunition. The only sale achieved so far is by IMI to Chile, to rearm some old tanks (apparently with a manually-loaded version of the gun).
The largest conventional cannon currently being promoted is the new Russian AU-220 turret containing a version of the old 57mm S-60 AA gun in 57x347SR calibre. This is initially intended for rearming the PT-76 light amphibious tank but is said to be suitable for other LAFVs.
Begleitpanzer Marder armed with Bofors 57mm gun (Courtesy Harry Zertner)
PT-76 with 57mm AU-220 turret
OTO Melara 60mm HVMS gun on Dardo IFV chassis
|20x139 (HS 820, US M139, GIAT 20M693, Rh 202), 25x137 (M242 Bushmaster), 30x165 (2A42, 2A72), 30x170 (Rarden), 30x173 (Bushmaster II / MK44, Mauser MK30), 30x210B (Zastava M86/89), 35x228 (Oerlikon KDE, Bushmaster III)||
35x228 (Oerlikon KDE, Bushmaster III), 40x364R (Bofors L/70, Bushmaster IV),
57x347SR (Russian AU-220M), 60x410R (IMI / OTO 60mm
For attacking other LAFVs the ammunition of choice has
developed from the APHC (armour piercing hard core) through APDS, and is now
APFSDS (Armour-Piercing Fin-Stabilised Discarding-Sabot), effectively a
miniature version of the principal Main Battle Tank AP ammunition. The
penetrators are almost universally of tungsten alloy, although the USA fields
the 25mm M919 DU round; the enhanced penetration which this provides helps to
compensate for the relatively low power of the cartridge.
In current service, the AP ammunition is supplemented by point-detonating fuzed HE for use against soft targets. However, the main focus for development in LAFV ammunition at the moment is airburst HE, using a time fuze.
Several drivers are pushing up the gun calibre of new LAFVs. One of them is that the armour protection of such vehicles is improving, as can clearly be seen as a result of operations in Iraq. The weight of existing LAFVs has been steadily increasing, mainly to add protection: over their lifetime, the M2 Bradley has increased from 23 to 30 tonnes, the Warrior from 25 to 32, the CV90 from 21 (prototype) to 35, the German Marder from 27.5 to 37.5, while the new German Puma weighs in at a massive 43 tonnes. This will require more powerful AP ammunition to achieve reliable penetration in the future.
The need to blow holes in buildings being used as cover also favours larger HE shells. But perhaps even more important is the current interest in airburst HE/fragmentation for attacking enemy forces hiding behind walls and other cover. This is known as HEAB (High Explosive Air Burst) or ABM (Air-Burst Munition). First in the field was a modified version of Oerlikon's AHEAD time-fuzed shrapnel ammo, available in 35mm and 30mm calibre and now redesignated KETF (kinetic energy time fuzed).
The 35mm KETF is available in a special anti-personnel loading containing 341 cylindrical tungsten sub-projectiles each weighing 1.5g (compared with 152 at 3.3g for the AA version). However, this only throws the fragments forwards, which may miss soldiers behind cover. Accordingly, there is more interest in HE/fragmentation shells which can be designed to project fragments downwards and even backwards, as well as forwards. If one of these shells, with a spherical fragmentation pattern, is detonated above a target, then only a small minority of the fragments will strike the targets. In these circumstances, shells big enough to produce a large quantity of fragments are clearly advantageous (especially as the time-fuze systems are very expensive, so maximising the "bang for the buck" is important).
|The picture on the right shows a 35mm APDS (in its sabot, and the flight projectile only) and a 25mm APFSDS.|
Puma with 30mm Mauser MK 30-2 gun
CV9035 with 35mm Bushmaster III
As a result of these issues, the minimum calibre being considered for most new LAFV developments is 30mm. Even that may be considered marginal in the long run, hence the current interest in several armies in 35mm and 40mm armament. This provides a measure of future-proofing; a wise precaution given that once a decision about a new gun calibre is made, it tends to be in service for several decades. It is significant that the Dutch study which led to the decision to select the 35mm calibre concluded that 30mm APFSDS would be inadequate to deal satisfactorily with the latest up-armoured versions of the Russian BMP-3. However, there are practical limitations on gun and ammunition size, especially in vehicles intended to carry troops as well as a gun. Perhaps of most significance is that the fact that many programmes will be to fit – or refit – new armament to existing vehicles, in which case the space available for the turret (and especially the diameter of the turret ring) can impose a significant limitation on the size of the gun and its ammunition feed.
There is therefore a trend to try to squeeze more performance out of existing guns by increasing their calibre. An example of that is the development of the 40mm ‘Super 40’, which is basically a necked-out version of the 30x173 case retaining the same rim diameter and overall length as the 30mm cartridge. It is therefore in principle a straightforward task to modify the externally-powered 30mm MK44 gun to take the Super 40 ammunition; it just needs a new barrel and some modifications to the feed unit. A few years ago, General Dynamics Ordnance and Tactical Systems (GD-OTS) were looking at different case lengths for the HE (164mm) and APFSDS (218mm) versions of the Super 40, but more recently have settled on a compromise case length of 180mm for both. At the same time the calibre has been reduced to 39mm to provide more case taper, but it is still referred to as a 40mm round. An earlier, similar, exercise was to neck out the 35x228 Oerlikon case to create the 50x330 ‘Supershot’. However, the Super 40 and the 50mm Supershot have not so far proceeded beyond the development stage: work on the latter has been stopped entirely, and while development of the Super 40 the former had been proceeding at a low level, GD-OTS seem to have recently accelerated work.
There is one Western programme which offers an alternative approach to the LAFV armament problem of providing high performance within compact dimensions: the Franco-British 40mm CTAS (Cased Telescoped Armament System) developed by CTA International, a joint project between Nexter (formerly GIAT) and British Aerospace. This uses very short, telescoped ammunition just 255mm long overall (the projectiles are entirely enclosed within the case) with a very high performance, approximately equal to that of the 40mm Bofors and the 50mm Supershot (all three cases having similar propellant capacities). The rim diameter of the CTAS round is the same as that of the Bofors 40mm case, but the Bofors round is twice as long. The gun installation is also designed to minimise turret intrusion: the ammunition is fed in sideways (pushing out the fired case as it does so) then the chamber rotated in line with the barrel to fire. The feed is on the axis of the trunnions, so does not move as the gun is elevated. There are clearly some significant advantages here, particularly in minimising the risk of failures to feed and in releasing a lot space in the turret (which looks quite empty compared with a conventional gun installation), although its competitors point out that the trunnion loading means that the gun is out of balance requiring more power for the elevation system, and argue that barrel wear is higher and the ammunition more expensive. However, the higher cost of larger calibre ammunition, plus the smaller quantity which can be carried, is counteracted by the fact that fewer of them would need to be fired to achieve the same effect.
The 40 CTAS HE projectiles weigh 1kg, about 1.5x more than the Super 40 and 2.5x more than the 30mm HEAB: muzzle velocities are similar at around 1,000 m/s. The APFSDS projectiles for the two 40mm rounds are launched at about 1,500 m/s, but again the 40 CTAS is heavier, thereby providing significantly more muzzle energy than the Super 40 (around 500,000 joules compared with c.340,000). However, the Super 40, at 44mm diameter, is significantly slimmer than the 65mm diameter 40 CTAS round, so a lot more ammo can be carried in the same volume.
The photo below shows experimental ammunition next to service rounds, all to the same scale: first, the 30x173, then the 40x180 Super 40 HE and APFSDS, next an experimental high-performance loading of the 35x228, then the 50x330 Supershot (and a sectioned example of the APFSDS loading) and finally the 40x255 CTWS (standing on its head!) and a sectioned 30mm Rarden APDS for comparison.
|The next photos show the 40mm CTWS and its ammunition. Note the sideways loading system through the trunnions and the very compact gun and ammo feed mechanism, which takes up little space in a turret.|
Warrior Capability and Sustainment Programme (WCSP)
The UK's Warrior Mechanised Infantry Combat Vehicle (MICV) is currently armed with the 30mm Rarden cannon in 30x170 calibre, as is the Scimitar Combat Vehicle Reconnaissance (Tracked) or CVRT. This gun led the field when first introduced in the 1970s but has since fallen behind, due partly to its slow rate of fire (exacerbated by its manual reloading, in 3-round clips) and partly because the mounting is not fully power-operated, let alone stabilised, so the vehicle has to stop to fire accurately. Furthermore, various attempts over a long period to introduce APFSDS ammunition failed to meet requirements until recently (when a modified version of the RWM projectile was chosen for the L21A1 loading), so the gun has been limited to APDS. The MoD has therefore established a requirement for a new gun armament for LAFVs which will be stabilised and able to utilise both APFSDS and HEAB ammunition, as well as featuring the latest sensor and defensive aid suites. The first beneficiary was planned to be the Warrior followed by a new reconnaissance vehicle, the FRES SV (Future Rapid Effect System, Specialist Vehicles) better known as the Scout., although priorities have recently changed due to the age of the CVRT and its vulnerability to roadside bombs in Afghanistan.
In 2005 the UK announced its intention of holding a competition for the gun element of the Warrior Fightability and Lethality Improvement Programme (WFLIP - formerly known as WLIP and now renamed Warrior Capability and Sustainment Programme or WCSP), with a calibre of at least 35mm being specified. However, in 2007 this was amend to allow 30mm guns to compete, and three of the four contenders chose to use ATK's 30mm Mk 44 (the marinised version of the Bushmaster II, which it has replaced in production), with a potential upgrade to the Super 40 calibre, as follows:
1. Lockheed Martin Insys (together with Rheinmetall Defence), based on a modified version of the existing Warrior turret.
2. GD-OTS, offering a version of their MK46 turret designed for the USMC's Expeditionary Fighting Vehicle.
3. Selex, teamed with OTO Melara to offer their HITFIST turret.
4. CTAI with the 40mm CTWS (which is also being considered for future French Light AFV requirements).
While the traditional manned turret is increasingly being challenged by remotely-operated overhead mountings, demonstrated by the new German Puma MICV fitted with a 30mm Mauser MK 30-2 cannon, WCSP requires a manned turret.
Interestingly, the increasingly sprawling BAE empire could have offered two other alternatives: the CV9035 turret with the 35mm Bushmaster III (with a potential upgrade to 50mm Supershot) and the Bushmaster IV in 40x365R Bofors (although it seems unlikely that the Bushy IV would fit into the Warrior's small turret ring). However, the company decided not to propose these, but to put its full weight behind the 40mm CTWS. Their first turret design was replaced by the MTIP 2, which was first test-fired in autumn 2007.
It was announced in March 2008 that the 40mm CTAS had been selected as the gun to be used in WCSP and FRES Scout, although not necessarily in the BAE turret. GD-OTS dropped out of the WFLIP contest, but Selex Galileo and Lockheed Martin both stated that they would produce turret designs for the 40 CTWS. However, by the end of 2008 Selex had dropped out leaving the competition between BAE and LockMart.
Warrior with 40mm CTWS in MTIP 2 turret
In October 2008 Lockheed Martin UK was awarded a study contract "to develop the performance, cost, time and risk information of a concept two-person turret and mission system for the FRES Scout". Originally the intention was to use the same turret for both WCSP and FRES Scout, but early in 2009 it was decided that FRES Scout would have a new turret optimised for the reconnaissance role. At the same time it was announced that there were two contenders for the FRES Scout chassis: the BAE/Hagglunds CV90 and the GD ASCOD 2, both of which are tracked vehicles currently in production. BAE proposed a brand new turret design for both FRES Scout and WCSP, with variations to take account of their different roles. LockMart proposed a modified version of the existing Warrior turret for WCSP, although it was not at that time clear which turret they would supply to GD for the FRES Scout.
In March 2010 the MoD announced that GD had been awarded "preferred bidder status" for FRES Scout. This does not mean that they will automatically be awarded the production contract, but it gives them a clear lead - a major blow to BAE. At the same time it was revealed that LockMart would be supplying GD with Rheinmetall Defence's Lance Modular Turret System for this project, with appropriate modifications to accept the 40 CTWS.
In February 2011 the MoD announced that it had rejected the BAE proposal for WCSP, leaving only LockMart in the running with their modified version of the existing Warrior turret. So LockMart has won both competitions, albeit with two entirely different turrets. One consequence of this is that BAE are likely to abandon the UK as a location for making AFVs once current contracts are completed.
By the Spring of 2011 both the FRES Scout
and WCSP programmes looked in doubt in the light of the severe cuts planned
to the British Army in general and armoured forces in particular. The
numbers of FRES Scouts to be ordered and Warriors to be improved were
expected be reduced substantially, giving rise to fears that this would hurt
the economic case for adopting a new gun and ammunition system to arm them.
However, in October the MoD awarded Lockheed Martin UK a £642m contract as
part of the WCSP project, to include the 40 CTAS.
Fielding is projected to begin in 2016. The government has also expressed a
commitment to the FRES Scout, although fielding might be delayed until 2020.
therefore now seems that both projects are very likely to go ahead,
although it appears that there could be some delay. LockMart were
supposed to have delivered turrets to GD for installation on prototype
FRES Scouts in Q3 and Q4 of 2012 but, as of June 2013, these were still to be delivered.
Looking further ahead, in 2012 BAE revealed a proposal for a new family of LAFVs in the 17 ton range, as potential international replacements for the CVR(T) family. One of these featured the 40CTAS.
The photo on the right shows the BAE 40 CTAS turret on a Warrior doing its stuff at a demonstration for the MoD in January 2009. You can see the fired case at the lower front of the turret, having just been ejected from the small port in the turret side.