|Vol. 10 No 1 February 2002 ISSN : 0971 - 4413|
120 Millimetre MBT Arjun Armament SystemA state-of-the-art weapon and ammunition system has been developed by the DRDO for the Main Battle Tank (MBT) Arjun by adopting novel design concepts and latest technological advancement at par with the industrially advanced countries. The system is capable of destroying modern heavy targets up to a range of 5000 m. All aspects leading to ergonomics, product reliability, maintenance, ease of operation, and futuristic performance enhancement have been incorporated in the design of the system.
The following indigenous technologies have been developed and established during the course of the system development.
Electro slag refined (ESR) steel for gun barrels
Partial length autofrettaging of gun barrels
High pressure packing rings for recoil system
Tungsten alloy penetrators
Fin stabilised kinetic energy shot
Special alloy steel obturating cups for cartridge cases
Semi-combustible cartridge case and primer
The 120 mm rifled gun for MBT Arjun is made of special steel produced by the latest ESR/Vacuum Arc Remelting process. This has enhanced the performance and fatigue life of the gun barrel. The gun barrel has been partially autofrettaged to a pressure of 800 MPa to achieve a proof pressure of the order of 612 MPa. This is the first indigenously developed gun capable of firing at such a high service pressure achieving muzzle velocity of 1650 m/s and above. Efficient fume extractor of the gun ensures that no toxic fumes are left in the crew compartment. The gun is fitted with FRP Thermal Insulating Jacket to obviate differential thermal effect, thereby enhancing the accuracy of the weapon system.
The Arjun recoil system is a compact, lightweight, short recoil hydro-spring type, capable of absorbing the thrust of high pressure and high velocity gun. The system consists of two hydro-spring buffers mounted diagonally to meet the stringent space requirement inside the fighting compartment. The innovative design of taper control rod gives uniform recoil and run-out, thereby enhancing the accuracy and life of the system and the high rate of fire. The high pressure and durable packing rings coupled with high surface-finish of mating components ensure longer life and high reliability. This is a sealed system, which requires practically no maintenance.
Two types of ammunition, namely, Fin Stabilised Armour Piercing Discarding Sabot (FSAPDS) and High Explosive Squash Head (HESH) have been fully developed and productionised for MBT Arjun.
The complete round of Arjun ammunition system consists of a semi-combustible cartridge case with steel obturating cup, semi-combustible primer, propellant, additive liner for wear reduction of gun and FSAPDS shot/HESH shell. The semi-combustible cartridge case (SCCC) ammunition has the advantage of reduction of round and chamber length, weight of the round, ease of handling, higher muzzle velocity, higher rate of fire, longer barrel life, and logistics.
Steel Obturating Cup
The SCCC technology is being used in the contemporary tanks. Steel cup is a major component of SCCC technology used for indigenous development of the ammunition for the Arjun tank, and has been designed, developed and productionised by the DRDO for the first time in the country. This component provides effective obturation during firing of the ammunition.
FSAPDS is the primary antitank ammunition for Arjun. The complete FSAPDS round consists of semi-combustible cartridge case, semi-combustible primer with steel obturating cup, triple-base propellant, and wear-reducing additive liner. The sub-calibre kinetic energy projectile has a very high-density long rod tungsten alloy penetrator enclosed in a three-piece sabot segment and a tail unit for in-flight stability with tracer. The shot is machined to a very high degree of precision with best CNC machines and online inspection to achieve the high standard of accuracy. This hyper velocity ammunition can defeat all the modern targets at a range of 5000 m and above. The accuracy and consistency of the shot is of the order of 0.2 mil standard deviation.
High Explosive Squash Head (HESH) is the secondary ammunition for Arjun and is effective against a variety of soft targets, tanks, fortifications, etc. The complete HESH round consists of a semi-combustible cartridge case, primer with steel obturating cup, and a single-base propellant. The optimised explosive composition of HESH defeats rolled homogenous armour plate detaching a scab of about 9 kg mass moving with a velocity of 100 to 120 m/s. Besides the scabbing effect, blast and shock imparts a tremendous jolt to the enemy tank stripping off explosive reactive armour and incapacitating the crew severely, thereby affecting their fighting capabilities. The accuracy of the HESH is of the order of 0.25 mil standard deviation.
The gun/ammunition system has been fully optimised and integrated with the MBT Arjun, meeting the stringent GSQR for consistency, penetration, lethality and high rate of fire. The production in ordnance factories has been well established. Strict quality control measures in the production stage and the final inspection stage are being maintained by DGQA/SQAE to ensure highest standard of quality.
Ordnance &Ammunition Data
|Calibre||120 mm rifled||Scab mass||9 kg|
|Breech type||Vertical sliding breechblock||Scab diameter||280 mm|
|Semiautomatic/hand operated||Scab velocity||120 m/s|
|Ordnance length||6050 mm||HESH/T 1A|
|Ordnance mass||2025 kg|
|Barrel life||500 EFC||Type of ammunition||Fixed SCCC|
|Muzzle velocity||735 m/s|
|Thermal Insulating Jacket (TIJ)||Round length||996 mm|
|Round mass||22 kg|
|No. of units||2 (front and rear)|
|Type||Split type, hinged||FSAPDS/T 1A|
|Recoil System||Type of ammunition||Fixed SCCC|
|Muzzle velocity||1650 m/s|
|Type||Hydro spring taper rod type||and above|
|No. of cylinders||2||Round length||940 mm|
|Normal recoil||350 mm||Round mass||20 kg|
|Recoil fluid||Oil mineral hydraulic buffer||Consistency||0.20 mil|
|Mass of each buffer||90 kg|
Arjun Armament System \ AMAGB for LCA \ Mobile Platform for Sarvatra \ Water Iron Removal Unit \ Conical Horn with RC Transit