Return of the one-o-five: the 105 mm gun might be regarded as the shooting star of the 20th century--its passage across the skies being a brief blaze of glory followed by oblivion. Yet, far from fading away, this ordinance is flaring back and becoming attractive for a wide range of duties.

At the beginning of the 20th Century the 105 mm howitzer was regarded as a means of augmenting smaller calibre (75 mm) field guns, but the first World War showed that these weapons were actually superior to field guns in terms of lethality. During the Second World War both the American and German armies made 105 mm howitzers the basis of their divisional artillery and afterwards many Western armies benefited from the cornucopia of American industry and continued to receive this ordnance.

During the Cold War the need for even greater ranges, lethality and increased mobility meant that, although 155 mm weapons became the basis of divisional artillery, new 105 mm weapons were produced. Oto Melara developed the Mark 56 pack howitzer--a 14-calibre weapon designed for mountain and parachute operations and weighing 1.29 tonnes in travelling order.The US Army decided to replace its wartime M101 24.5 calibre weapons and M2 gun with the lighter 32.2 calibre M102 and M137 gun, which could use the same ammunition.

Foreign Military Sale procedures meant the M102 was used by eleven armies, mostly in South East Asia and Latin America, but it was replaced in US Army service by the British Light Gun. The BAE Systems Land Systems (formerly Royal Ordnance) L118 was designed to replace the Oto Melara Mark 56 but with longer range and greater stability. This 30-calibre weapon features a unique bow-shaped tubular steel trail and weighs 1.86 tonnes both travelling and deployed and has a maximum range of more than 17 kilometres. The weapon proved extremely popular with 18 customers, some of whom replaced the original gun with the M101's M2 gun in a mounting designated L119 by the manufacturers and M119 by the US Army.

To meet the obvious demand the North China Industries Corporation (Norinco) developed a weapon with many similarities to the Oto Melara M56, while Giat produced the LG1, which weighs only 1.52 tonnes, the latest Mk II version having an autofrettaged barrel to enable it to operate with higher-pressure ammunition. The LG1 included a new range of ammunition with both enhanced range boat tail and base-bleed projectiles. The ammunition can be used from other 105 mm guns but with the LG1 Mk 2 the latter has a range of up to 17.5 kilometres. India developed its own Light Field Gun, which is similar to the L118.

A number of companies have produced upgrade packages for the M101. Giat's package is based on the replacing of the gun with that of the LG1, and while the upgraded weapon can weigh up to 2.5 tonnes the Giat package has been acquired by two south-east Asian armies. RDM Technology of the Netherlands also offered new barrels, a 33 calibre one for standard weapons and, in association with Royal Ordnance at the time, 37 calibre barrels compatible with the L118 and a 30 calibre with the L119. The Dutch company has also proposed a 33-calibre upgrade for the M102.

Yugoslavia produced a weapon, confusingly designated M56, combining the M101 with the German Leichte Feldhaubitze M18/40, and this too had some export success. Korea's Kia Machine Tool Company produced the KH178, which combined aspects of the British Light Gun and a Rheinmetall upgrade package.

Limelight Again

Strangely the value of the 105mm weapon has increased in the post 9/11 world and continues as armies seek to meet asymmetric threats. With the importance of urban operations and the fear of 'collateral damage', the 105 mm projectile has a more compact bursting area than a 155 mm warhead. With the latest generation of muzzle velocity measuring systems the 105 mm gun can also deliver its round with far greater precision than 155 mm weapons.

The one-o-five is also inherently more mobile because it is lighter and more compact. The complete gun can easily be slung beneath a medium lift helicopter or towed by any 4 x 4 Jeep-type wheeled vehicle, and the relatively low weight of its ammunition allows more projectiles to be brought into the field. They do not have the wide variety of specialised munitions available to 155 mm weapons, but it is significant that when BAE Systems developed a new Insensitive Munition filling the first artillery projectiles to receive it were for 105 mm weapons.

More armies are now recognising the value of these compact but deadly weapons. For this reason the US Army intends to acquire another 200 M119s to replace the M102 in National Guard and Reserve units. While the Pentagon has opted for 155 mm for the Nlos-C (Non-Line Of Sight-Cannon) of the Future Combat System programme, although the airlifting constraints of the vehicle design will make this technically challenging, the US Army seems likely to select a 105 mm system for its Enhanced Forcible Entry Cannon requirement with an in-service date of 2012. The new weapon is to weigh less than 1.9 tonnes, including a digital fire control system and will have a 20-kilometre range with ammunition such as the General Dynamics/Denel Igala while remaining compatible with existing 105 mm ammunition.

BAE Systems is likely to offer either the M119A1 or a series of incremental improvements leading to the Super Lightweight Howitzer. The first stage involves an improved recoil system, suspension and tyres together with an integrated automatic pointing system. The second stage modifies the wheels to ease folding and unfolding of the gun, introduces new spades and a modified muzzle brake to reduce peak overpressure. The third would introduce new technology such as 'soft' recoil, a split-trail carriage to reduce weight and improve stability as well as the introduction of a new barrel.

The British Army intends to retain the L118 until 2033 but upgrades are envisaged to meet the Lightweight Mobile Artillery Weapon System (Gun) or Limaws (G). This might well include the incremental changes mentioned above but the first stage is the introduction of the new insensitive munition high explosive shell. In terms of ballistics this will be identical to the L31 shell it replaces but will increase lethality by 20 per cent. BAE Systems and Rheinmetall have developed a new smoke round for this weapon using red phosphorus to provide bi-spectral screening.

Giat is already enhancing its LG 1 Mk 2 system. The Mk 3 features auto-positioning and command post integration while a vehicle-mounted version, the Mk 4, anticipated to be available from next year, will feature automatic laying. This latter version will be upgraded to Mk 5 status about 2010 with a fully automatic loading system. It is anticipated that AAI will propose a version of LG1 for the Enhanced Forcible Entry Cannon requirement.

The importance of 105 mm weapons may be gauged from the fact that Denel Ordnance has been developing a technology demonstrator known as the 105 mm light experimental gun called Leo. This is a 52 calibre weapon which can fire a new range of base bleed projectiles up to 30 km, making it similar in performance to 155 mm weapons, although conventional munitions have a 24 km range.

Originally developed for the South African Army it is now being marketed abroad and attracting considerable interest. The prototype weighed 3.8 tonnes but work is continuing to bring this down to 2.5 tonnes with various carriage options also being pursued.

United Defense, which is now under the BAE Systems fold, is likely to offer a towed version of its developmental V2C2 (Variable Volume Chamber Cannon) hybrid howitzer. This features a unique breech assembly incorporating a sliding block or breech carrier that supports an interrupted screw-thread breech plug/seal assembly. Because this provides a variable intrusion the volume of the chamber can be adapted to meet the projectile and modular charge system.

The principle has been demonstrated since early 2004 using the existing range of 105 mm projectiles. In terms of range it would appear that 24 km can be achieved with conventional ammunition and about 30 with rocket-assisted projectiles, making this an extremely interesting concept.

While the 105 mm gun may lack the range of sophisticated munitions available to its bigger cousin this does not mean that such ammunition is lacking. Carrier rounds with dual-purpose grenades have been developed by Pyrkal and Israel Military Industries the latter as the M116.IMI has further developed its M116 cargo round to produce the Hornet. This replaces the 15 grenades with 42 Hornet bomblets which are available in both antipersonnel and anti-armour versions.

In association with the Leo programme Denel Ordnance has been developing a range of ammunition under the name Igala that has been evaluated by both the British and US armies. They are HE and HE fragmentation, visual and infrared illumination, smoke and practice rounds and are available in both boat tail and base-bleed versions.

The vast majority of 105 mm guns are towed but alternatives means of improving their mobility have been explored. One of the few self-propelled mountings was the US M108, but this has been largely replaced and a more profitable means of improving mobility may have been demonstrated by RDM who has developed the Mobat (Mobile Artillery), consisting of one of its upgraded 105 mm weapons on a DAF YA 4440 cross-country 4 x 4 flat-bed truck (see Armada International 4/2005, page 48).

A self-propelled Leo system is under development in association with General Dynamics Land Systems-Canada. This is based upon the latter's 8 x 8 light armoured vehicle, a prototype of which appeared in 2004. Another version proposed would be based on a 6 x 6 Tatra 815 truck.

On Armour

The most mobile 105 mm weapons are those in armoured vehicles. For some two decades from the mid 1950s the 56-calibre rifled 105 mm L7/M68 gun was the standard weapon of Western main battle tanks, but was then supplanted by the 120 mm smoothbore. The value of this calibre weapon in armoured vehicles remained appreciated and by using long recoil strokes and muzzle brakes it was possible to incorporate them in smaller, wheeled vehicles which could retain their mobility (both strategic and tactical) and offering a punch similar to that of a main battle tank.

The Giat F-2 semi-automatic weapon is used in the AMX-10RC 6 x 6 and Mowag Piranha II reconnaissance vehicles. It features a brake on the left-hand side and a counter-recoil mechanism on the right. The armour-piercing, fin-stabilised discarding sabot round can penetrate most tank armour at a range of two kilometres. The South African GT-7, which is offered in the Rooikat 4 x 4 reconnaissance vehicle, features a different approach: a hydro-pneumatic recuperator with a liquid accumulator and a barrel sleeve of different diameters on either side of the recoil piston.

Oto Melara developed a low recoil force gun that is used in the Centauro 8 x 8 tank destroyer produced for both Italy and Spain. This calls on a high-efficiency muzzle brake based on 'pepper box' and gas deflectors, a long (740 mm) recoil length and coaxial brakes. The company has also developed a new 120-calibre 105 mm rifled gun for its Hitfact turret system, which is also compatible with a 52-calibre 105 mm gun and a 45-calibre 120 mm gun.

Despite its operational advantages the low recoil 105 mm gun has tended to be overshadowed by the 90 mm medium-pressure guns such as the Giat F3 and the Cockerill Mark 8. But it is now recognised that these are no longer powerful enough against the main battle tank armour and this may well stimulate renewed interest in the low recoil 105 mm.

During Eurosatory 2004 Cockerill displayed an improved 105 mm gun for armoured vehicles. The Cockerill CV has the same rifling and chamber volume as the L7/M68 but with a 20 per cent higher operating pressure limit and a recoil force of less than 15 tonnes. It has been demonstrated on a Piranha III and will be supported by a new Mecar M1060CV armour-piercing sabot round.

It has been reported that a 105 mm main armament is preferred for the Mounted Combat System of the US Army's Future Combat Systems. Rheinmetall is currently developing two smoothbore guns to meet this requirement as RH 105-20 and RH 105-30 with a 51-calibre barrel, the former having a muzzle brake that reduced firing stresses by a third. Two versions are proposed of each with a standard 8.7-litre chamber and a 9.6-1itre one, the latter a product-improved version.

Ammunition for these weapons is being developed with Alliant Techsystems (ATK) with high explosive, kinetic energy and practice rounds. The combat rounds are essentially scaled down versions of Rheinmetall's 120 mm tank gun rounds.

The low recoil guns can accept the full range of tank ammunition and, it is believed, the products of two unusual ordnance programmes. Diehl, Krauss-Maffei Wegmann and KBP Instrument Design Bureau have proposed adapting the last company's 9M117M gun-launched missile technology to 105 mm guns. The programme, known as Spear, was for an infrared guided missile that could be handled in precisely the same way as a conventional round. However, the present status of the programme is unclear with few recent reports of activity.

Meanwhile Israel Military Industries and Rafael are developing the Excalibur guided round for both 105 mm and 120 mm guns. The projectile features aerodynamic surfaces that deploy after it has left the muzzle and it can engage targets out of the direct line-of-sight; although the manufacturers have not indicated whether millimetric wave or electro-optical sensors are used.

A few years ago the demise of 105 mm calibre guns in land warfare was widely predicted. Now it appears, as with Mark Twain's premature obituary, that reports of that demise were greatly exaggerated.