Try on a 120 for size. (Upgrades).

One of the three tenets of upgrading armoured fighting vehicles, alongside enhancing mobility and survivability, is improving firepower. For main battle tanks, the weapon of choice over the past 25 years has been the 120 mm smoothbore. Despite various programs investigating, developing and testing 140 mm guns, the one-twenty remains supreme in the medium term.

There are three 120 mm-armed gun turrets as available as 'drop-ins' for tank retrofit. These are from a Franco-Slovakian collaboration on the T-21 low-profile turret, Jordan's King Abdullah II Design & Development Bureau (Kaddb) Falcon and Italy's OTO Melara with its Hitfact turret mounting either a 120 mm L45 or 105 mm L52 gun. Another innovative option, proposed by General Dynamics Land Systems to Turkey, for the upgrade of M60s, was dropping-in the turret of an M1A1 Abrams, which was not, in the event, selected but remains on the table for other customers.

In exploring these programmes in more detail, one engineering viewpoint we find is that, in order to up-gun a tank, it is considered better to design a new turret (to fit the existing chassis) around the gun and its systems. In theory, this minimises the many problems associated with installing a new gun, autoloader and other systems into an existing turret.

It was such thoughts that led to France's Giat and DMD of Slovakia to collaborate on the T-21 low-profile turret study. It was designed to be dropped onto a T-72 MBT without incurring additional weight penalties. The philosophy is one of using off-the-shelf components to keep down costs and development time

As was explained at the Eurosatory 2000 exhibition, the T-21 is a 15-tonne turret armed with the Giat 120 mm F1 smoothbore gun and autoloader from the French Leclerc, complete with electric drive, digital fire-control system (with hunter/killer modes), open-architecture vetronics (vehicle electronics) system cum databus (for integration of a battlefield management system and a defensive aids suite) and an add-on armour package. Although protection against hollow-charge and kinetic energy warheads has been reduced on the frontal arc to save weight, Giat offers modular armour packages.

As yet, no full-scale hardware is believed to have been built, although the scaled-down model, photographed by Armada's Editor-in-Chief (title picture), depicts the general proportions of a T-72 thus armed. The companies are looking for a firmer commitment from potential customers and propose forming an 'industrial club' for production.

Jordan, anxious to develop its own industrial capability through the Kaddb, has been working on a new 120 mm-armed turret for some years, via an international team. The Falcon turret, designed in collaboration with the Mechanology Design Bureau of South Africa, uses the Swiss Ruag L50 120 mm smoothbore Compact Tank Gun (CTG) with a 10-round, bustle-mounted horizontal autoloader from FHL Claverham (giving a reported rate-of-fire of eight rounds per minute) and provision for a further 14 rounds in the hull.

A Thales Optronic electro-optic suite has been chosen (although other systems could be used). IST Dynamics is responsible for the turret's electronics and system-integration work, while CLS Systems deals with the power management.

Originally developed as the AB9C4 for the Tariq (Centurion), with a view to upgrading and exporting surplus vehicles, the turret can be adapted to fit M60s, T-55s or AMX-30s. The current project is known as the AB9C5 Falcon 2 and is intended for the Al Hussein (Challenger 1) and, possibly, the Al Kahlid (enhanced Chieftain). A prototype turret on an Al Hussein chassis was scheduled to appear at the Idex exhibition at Abu Dhabi in March 2003.

The three-man Hitfact turret from Italy's OTO Melara is intended to mount a low-recoil gun--either the 120 mm L45 or 105 mm L52--for use on wheeled or tracked armoured fighting vehicles. The auto-frettaged gun (of either calibre, featuring a thermal sleeve, bore evacuator and multi-baffle muzzle brake) is mounted on a hydraulic recoil/counter-recoil system, minimising stress to the turret and chassis.

In addition to the main gun, the turret features an independent turret-on-turret, equipped with a 7.62 mm machine gun and infrared camera, controlled by the commander. The gunner is provided with a self-stabilised day sight and a periscope-mounted second-generation thermal camera for night work, with an integral eye-safe laser rangefinder.

Although prototyped with a 105 mm gun on the Centauro 8 x 8 wheeled AFV, a 120 mm version has yet to be built or fitted onto an MBT chassis.

Initially proposed to Turkey as far back as 1998, the General Dynamics Land Systems (GDLS) M60-2000 project involved dropping the complete 120 mm M256-armed turret of an M1A1 Abrams MBT directly into an M60 chassis, as well as providing a new powerpack. The company considers this to be a highly effective upgrade package and is aimed at countries that have received M60s as part of the 'cascading' process following the downsizing of the US Army.

With over 900 M60s, Turkey was a prime candidate for this package as it had an industrial capability to undertake the main upgrade in-country. In the event, the competing Israeli solution (see below) was adopted. GDLS continues to offer this option to potential customers.

One variation is to replace an existing gun with a better version of the same. In the case of Germany's Leopard 2A6 programme, this involves replacing the Rheinmetall 120 mm L44 smoothbore gun with the longer-barrelled L55. With an increased length of 1.3 metres, the L55 version has a significant increase in muzzle velocity. This is particularly noticeable when using the latest version of DM53 armour-piercing fin-stabilised discarding-sabot--trace (APFSDS-T) ammunition, with a non-depleted uranium penetrator. Additionally, the company claims a greater armour penetration and increased combat range of the weapon to 1600 metres.

According to Rheinmetall, a 14 per cent increase in muzzle energy is registered on the L55 as compared to the L44 version when using APFSDS rounds. The geometry of the gun's chamber remains the same as the L44, which allows all existing L44-compatible natures to be fired.

Commonality with the L44 continues by the using of the same interface measurements to the breech and cradle, allowing replacement of barrels to be accomplished relatively easily. As the L55 weighs 1347 kg compared with the L44's 1190 kg, the recoil brakes and trunnion bearings are strengthened. Rheinmetall supplies the Leopard's manufacturer, Kraus-Maffei Wegmann, with the replacement kit, which is then installed on the Leopard, producing the 2A6 model. In addition to the new barrel, the kit comprises the muzzle reference system, breech, breech guard, thermal sleeve and steel shell-case holder.

With plans for 350 upgrades, the first was handed over to the German Army in March 2001. This retrofit programme has also been adopted by the Netherlands (180 tanks) and Spain for its 219 new-build Leopard 2A6s. The US Army, which uses the L44 barrel with a re-designed breech, as the M256 on the M1A2 Abrams, has procured a trials batch of L55 kits for evaluation.

The Leopard 2A6 programme involves replacing one 120mm gun with another. To improve the M60's firepower, however, the original 105 mm must be replaced with a 120 mm gun, a slightly more engineering intensive process. There are two known 120 mm M60 up-gunning programmes involving the existing turret. For its M60s, Turkey has selected the Israeli Military Industries (IMI) Sabra solution, while Jordan's Kaddb has brought together an international team to develop another M60 solution using (for the first time) the Swiss Ruag L50 120 mm smoothbore CTG.

IMI's MG251 120 mm gun, which is similar to Rheinmetall's L44 but with a different recoil system and more compact dimensions, was developed for Israel's Merkava Mk 3 and Mk 4 tanks and fires IMI's bespoke range of 120 mm ammunition. It can, however, also fire French, German or American natures if needed.

It is this gun that is the core of the Sabra up-gunning programme for the M60. Exact details of the conversion remain classified but the barrel and breech mechanism are new, while the mounting needs modification and the ammunition racks of the M60 need to be modified to accommodate the longer and wider 120 mm rounds.

Teamed with Elbit, ElOp and Nimda, IMI has offered the Sabra on the export market and Turkey is planning to upgrade its 170 M60A3s, although the decision is somewhat controversial as there was no real competitive programme prior to selection. IMI continues to market the Sabra to other M60 operators.

Jordan's project to improve the firepower of its fleet of M60s via an upgrade, now known as AB9B1, was first announced by what is now Kaddb at the Idex exhibition in Abu Dhabi in 1999. An M60 had been fitted with a 120 mm CTG non-firing gun installation, provided by SW-Thun (now Ruag Land Systems) of Switzerland, for display purposes.

The Kaddb approach was to devise a tank that is 'mission capable, but affordable' by focussing on the M60's primary deficiency, which is assessed as lethality. Once developed, it was proposed to market the upgrade to the various operators of the M60 in the region.

At the Sofex exhibition in April 2000, it was announced that Raytheon Technical Services Company (formerly Hughes) had been awarded a contract to supply and fit an integrated fire control system (IFCS) to a 105 mm-armed M60A3. Unlike the original tank thermal sight, the IFCS provides a shoot-on-the-move capability. Various other international contractors were involved in supplying and installing equipment.

By Idex 2001, an installation with both the IFCS and 120 mm CTG was complete and operational and trials were conducted in May 2001. Kaddb stated that the integration work carried out thus far had quashed doubts about the feasibility of installing the 120 mm gun in the M60 turret, but declined to be specific. Raytheon was, however, devising new software for the IFCS to support the 120 mm CTG. Ruag had a already qualified the weapon to fire the full range of Giat 120 mm ammunition, including practice, kinetic energy and Heat ammunition, using Giat-supplied 'overspeed/overpressure' qualification rounds.

On 18 March 2002, the Jordan Arab Army announced it was to modernise a portion of its M60A3 fleet using elements of the Kaddb AB9B1 upgrade package. The project encompasses a three-tier modernisation: Level 1 introduces fire control improvements for the existing M68 105 mm rifled gun, augmented in Level 2 with a firepower upgrade, and in Level 3 with automotive and protection enhancements--the latter only to be undertaken if affordable.

At that time it was stated that all developmental work required for integration of the Raytheon IFCS with the existing M68 105 mm-armed M60A3 had been completed, and that the Level 1 version was being readied for production, both for Jordan and for prospective export customers.

Kaddb pressed forward with completion of development of the Level 2 AB9B1 variant, an M60A3 upgunned with the 120 mm CTG. Working alongside Cadillac Gage and Ruag, Kaddb's goal in the latest round of tests was to evaluate the shock and vibration profile of the M60 turret's complete hydraulics system when it was used in conjunction with the 120 mm CTG gun, to ascertain whether these are sustainable by the existing system. Monitored with the aid of a new Kaddb-developed ballistic data-collection van, firing trials were staged in April 2002, and the resulting dispersion data is being used to develop revised ballistic data for the Raytheon IFCS.

According to Kaddb, although the 120 mm CTG is twice the weight of the M68, it proved to be very well balanced, producing a virtually identical curve for platform speed and standard deviation to that obtained with the M68. Consistency had also been impressive in static tests, the source stated, four rounds having hit a 10.16 x 5.08-inch target at 1 km in 43 seconds (using a boresighted gun). The impending (at the time of writing) Idex show in March 2003 should bring further details of progress.

A fourth 120 mm up-gunning programme has been jointly developed by the Ukrainian Kharkov Morozov Machine building Design Bureau and the State Enterprise Malyshev Plant, whereby a T-72 has had its existing 125 mm weapon replaced by a Nato-standard 120 mm smoothbore gun.

A prototype installation was displayed at Idex in March 1999, fitted with a 120 mm gun believed developed by the State Scientific and Technical Centre of Artillery and Rifle Arms. It uses, Ukrainian sources said, a modified 2A46M breech mechanism and has a bustle-mounted automatic loader, carries 22 separate loading rounds (projectile and charge) in the bustle and another 22 in the hull and can fire standard Nato types of single-piece ammunition.

This prototype installation also featured alternative diesel powerplants and the option of a French Sagem-15 day/night (thermal) sight and a Sfim (now part of Sagem) VS 580 stabilised day/night sight for the commander, with optional laser rangefinder. A computerised fire control system is also installed, allowing hunter/killer target engagements to take place.

According to Ukrainian sources, the same weapon system could also be retrofitted to T-64s, T-80UDs and T-84s. However, since 1999, there has been no further progress reported and the project's status is unknown.