Israeli Military Vehicle Research

The Chilean Army and the IMI 60mm HVM gun  by Fernando L Wilson

In the early 1980s, the Chilean army was facing the prospect of a second decade of border tensions with its three neighbours, Peru, Argentina and Bolivia. Combined with this an embargo that impeded the regular flow of weapon systems from its traditional suppliers. This situation had already contributed to a couple of very serious war scares during the seventies. The first when Peru became a Soviet client state and received massive defense supplies and the second when the Argentinean military government threatened war against Chile over the possession of three islands to the south of the Beagle Channel, in the austral area of the border between both countries.

On both occasions, the army's needs were met by a combination of local effort to develop and maintain old weapon systems and by acquiring other weapons systems from countries that did not support the embargo. A leading supplier in the second situation was the State of Israel. In the mid to late 70s, it had supplied Shafrir AAMs to the Chilean Air Force, and then over 150 M51 Sherman tanks to the army. By the early 1980s, it was a reliable and dependable supplier.

The problem the army faced was the need for an significant boost to its anti-armour capability. This was already stretched to the breaking point by the then current levels of the perceived threat. Army evaluations suggested that during the 1980s, its anti armour capabilities would be exceeded by the rearming of some of its immediate neighbours. Peru was suspected of trying to replace its older and most worn out T55s with either uparmoured variants of the T55 or the more potent T62s.

A number of options were evaluated, including 90mm armoured Scorpion CVR(t)s, Chinese MBTs, etc. But all these options were rejected by one reason or another.

One system, among those offered, caught the attention of the evaluation committee. It was an Israeli gun called the HVM or Hyper Velocity Multipurpose gun. It was a small 60mm gun that provided high velocity kinetic energy projectiles to penetrate unheard of amounts of armour at considerable ranges. Up to that date, the main western armour defeating system had been the use of the Monroe principle hollow charge, also called HEAT (High Explosive antitank). This works on a chemical principle that does not’t require high muzzle velocities to work. Something thought vital at a time when NATO faced the veritable soviet hordes, equipped with potent well armoured tanks. This system needed great calibres to enhance its penetrative power, so it became quite common to fit relatively large low pressure guns to very small vehicles. The French Panhard AML90 (90mm gun) is a good example.

The soviets, which quite clearly understood the capabilities of HEAT, began developing technological approaches to defeat the menace of HEAT charges. They were the first to deploy a composite armour (called "Combination K") on the T64 tank. The West was not’t to far behind, and the appearance of ERA or reactive armour was immediately followed by advanced composites like Chobham or Burlington. The HEAT had reached a physical dead end, and although combined and tandem warheads and top attack profiles saved the day for antitank missiles fitted with this type of warhead. Tanks shells had to look for a new option.

The option was to resurrect the APDS (armour piercing discarding sabot) principle first deployed by the British Army in the latter days of WW2. It consisted in firing an extremely dense though thin penetrator, surrounded by screens of a lighter material which peeled away after exiting the barrel. This left the penetrator to fly at extremely high velocities and transfer a larger amount of energy to the target than it should be the case with a large diameter slower round. Additionally, the availability of newer highly dense materials such as new Tungsten Steel alloys and eventually depleted uranium, made this option the choice of the day for the NATO tank weapons of the 1980s and 90s.

In this field, the Israelis developed their own hard hitting first generation APFSDS round called the M111, This was developed for use in the L7/M68 105mm guns fitted to the Patton, Centurion and first generation Merkava tanks. The lethality of this round was proved beyond any doubt in the confused tank battles in Lebanon during 1982, where it was able to kill even the vaunted T72 tank.

After this success, and through a market research effort, IMI detected that the light AFVs up to then armed with high caliber low pressure weapons could not make the transition from HEAT to APFSDS successfully. They were limited by the low internal pressures that their barrels could handle, thus, IMI then began to develop a new weapon to use a down scaled variant of the M111 round able to be fitted to lighter vehicles. The weapon they choose was a 60mm gun developed by the Italian firm of Odero-Terni-Orlando, better known as OTO, and that was derived from its extremely successful 76/62 compact naval gun.

This gun was then the subject of a co-development between IMI and OTO, that then came to light around 1983, being offered as an alternative to the more common 90mm low pressure guns then offered around the world. It was at first offered in a complete turret form, including an integrated fire control system, Laser rangefinder and night vision systems. It also had an automatic loader that enables it to fire 3 round bursts. Another version was for an "infantry gun" that was mounted on a tubular frame system to be towed and fired in the battlefield by an infantry party in the same way as an antitank missile launcher. The advantage was a far cheaper cost per round and a real multipurpose support ability through the use of different ammunition types. This spurred the development of a wide range of rounds for the gun, including HE-FRAG, WP, etc. Nothing came of these marketing efforts until around 1983 when the Chilean army expressed an interest in the weapon.

It fitted nicely into the Chilean requirement of lethality and small size, and found its first application in the modernization of the M24 light tanks then in use. The M24s offered a combination of capacity the Chilean army was keen not to lose. The M24s had a level of protection that ensured invulnerability against 20mm armour piercing ammunition while at the same time being light enough to operate in the southern Pampa, plagued with swamps and bogs which impede the use of heavier AFVs.

The modernization package was extensive and went far beyond the firepower issue, including a new engine and transmission, new fire controls, night vision systems and a complete overhaul of the hull. Thus, the gun had to be adapted to fit within the system being undertaken by the Army Workshops, FAMAE. The Chilean version disposed the automatic loader, which they felt was too bulky, complex and slow (and unnecessary, given the small size of the rounds, there is the rumour that this system was based on a similar one employed in the soviet BMP1 IFV). This required a completely new recoil system, which was subcontracted to the steel manufacturing company MADECO, that had already made many contracts for the Army, and produced the system to full satisfaction of the customer. The net result was that the Army was extremely pleased with the results and the programme was extended to some 50 tanks and opened the door to fit the weapon to more of the Armies platforms.

One of the key issues was how to provide a higher lethality to the Armoured Cavalry Regiments deployed against the Peruvian frontier in the far north. The MBT acquisition had failed because of the embargoes and the available alternatives, such as the Chinese T55 derivatives that were of poor quality and were ill suited for the peculiar conditions in Northern Chile. This area of Chile featured desert and mountains with an extremely high temperature coupled with abrasive winds and fogs carrying the nitrate rich sand.

The experience with the M51 (M50???), though, had been excellent. The Sherman chassis was simple to maintain and support and the 30-ton Sherman hull was narrow enough to adapt well to the narrow mountain roads. Additionally, the system was already in use and the respective training courses and spare stocks were available. To expand the system was a simple decision. The problem was that the Israelis were running out of Sherman chassis. This required searching throughout both Israel and Chile to find stocks and that produced some very odd combinations. The final result was an extremely odd vehicle, which very well can be called the very last fighting Sherman, called the M50/60.

This saw a more complete version of the 60mm gun fitted with an extensive fire control system fitted to an original M50 turret. The hull also received a modern integrated power pack and new communications together with a complete factory level reconstruction. This was too complex to carry out in Chile, particularly when FAMAE had its hands full with the local production of the Mowag Piranha vehicle, as it was supplying the armoured hull assemblies to the private contractor Carlos Cardoen, who then completed the final assembles of the vehicles. Thus, the responsibility was laid in the Israel firm NIMDA; by the end of the 1980s it had delivered more than 60 complete vehicles to the Chilean Army. These are so well regarded that they are still deployed alongside the new Leopard 1V MBTs in northern Chile, at the Vencedores Armoured Cavalry Regiment.

In 1989 democracy returned to Chile and this ended the embargoes, which had affected the Army for so long. At this moment the options for more potent AFVs were open and thus several hundreds of AMX30B2 and Leopard 1Vs were obtained, managing to complete the TOEs and discard the older and mostly worn M51s.

The need for a more complete armoured reconnaissance vehicle was recognised and FAMAE began to tinker again. This time the options were more complete and potent, and several prototypes were completed. Among them, a Mowag Piranha 6x6 was fitted with the complete Israeli turret, the 60mm gun fitted with a thermal shroud and other improvements. Another option is an 8x8 chassis fitted with a Cockerill 90mm gun turret. These remain at the prototype stage, as the Army has preferred to concentrate its limited funding in buying Cold War surplus vehicles rather than invest in the more expensive local production. This will change as the requirement for such a recce vehicle is climbing in the priority list as the MBT and APC inventories finalised. The experience of the Army with the 60mm gun is excellent and there is a strong intention to retain its services beyond the lives of the M50s and M24s.

As of 2002 there are several European prototypes using the HVM gun, such as an APC derivative of the Italian Centauro armoured car, the Dardo IFV and several Polish IFV proposals. So far, only a small Army at the end of the world has used this excellent weapon. May it be that others can use it successfully, particularly now that many countries are finding its IFVs to be under gunned with only 25mm weapons. It surely deserves more extensive market success.