CBS-321 155 mm gun

CBS-321 155 mm tank gun
Type	Tank gun
Place of origin	Carthage
Service history
In service	2011-present
Used by	Carthage Gensokyo Republic Japan Rhamos
Production history
Designer	Army Ballistics and Gunnery Research Center
Designed	1995-2006
Manufacturer	Butare Army Arsenal Philosir Precision Instruments Kaohsiung Arsenal
Produced	2008-present
No. built	19,250
Specifications
Weight	4,250 kg (9,370 lb) gun + mount
Length	7.44 m (24.4 ft)
Barrel length	46 calibers
Caliber	155 mm (6.1 in)
Breech	Vertical sliding block
Recoil	400 mm (16 in)
Rate of fire	12 rounds per minute (maximum)
Muzzle velocity	1,670–1,730 m/s (5,500–5,700 ft/s) with APFSDS
Effective firing range	5 km (3.1 mi) with APFSDS
Maximum firing range	12 km (7.5 mi) with guided munitions

The CBS-321 155 mm gun is a smoothbore tank gun used to arm the Carthaginian HTA-02 Jaguar II main battle tank. Designed by the Army Ballistics and Gunnery Research Center, the CBS-321 replaces the older T-17 120 mm smoothbore gun used in the HTA-01 Rhinoceros as the primary armament of Carthaginian main battle tanks.

History

The smoothbore 120 mm L/44 T-17 gun introduced in the MBT-74 Rhinoceros was originally expected to have a service life of 25 years into the late 1990s, by which point defense analysts expected improvements in European armor technology, new vehicles, and improved technology would necessitate a replacement. In response to this projected need, several new programs were initiated at the Army Ballistics and Gunnery Research Center (ABGRC) in the 1980s to study advanced gun concepts and technologies including electrothermal-chemical technology, bulk-loaded propellants, electromagnetic firing systems, and large-caliber conventional guns with various recoil and weight reduction measures.

By 1988, four prototype guns in the 120, 130, 140, and 155 mm calibers were produced as technology demonstrators, using new lightweight construction with higher strength steel and a fiberglass overwrap for additional strength. While sharing the same caliber as the original 120 mm L/44 T-17 smoothbore, the 120 mm L/55 T-20 gun developed for the program was 300 kilograms (660 lb) lighter in spite of being eleven calibers longer, resulting in a higher muzzle velocity and improved penetration over the original T-17. The other three test guns shared the same technology and were substantially lighter than previous weapons in these calibers.

Combat experience in the Second Pacific War against improved European main battle tanks such as the Leopard 2 and Challenger 1 indicated that even the improved T-17A L/50 gun was already becoming insufficient against modern threats and the T-20 demonstrator gun was quickly developed into a production-ready configuration, reclassified as the T-17S and introduced in the MBT-74AM2 modification as an immediate response to the situation. Development work continued on larger caliber solutions with the expectation within ABGRC that one of these would be selected to arm the proposed replacement for the MBT-74, the nascent Next Generation Main Battle Tank.

In 1999, the Next Generation Armor Conference held in Econiapolis resulted in significant changes to the performance requirements for the NG-MBT program, including a decision to retain the 120 mm caliber. These changes were made due to the conference's decision to keep the weight of the proposed tank to 55 tonnes and to rein in expected costs. The final design was expected to use a product-improved version of the L/55 T-17S gun with new ammunition in order to maintain lethality against likely threats and a slightly roomier hull with more efficient ammunition stowage. Work on larger caliber guns continued but primarily as a means of developing new technologies expected to be used in land and naval artillery applications.

The NG-MBT program was cancelled less than three years later in response to the announcement of the European-Venetian Liberator tank program, which was now a far more ambitious project than expected. The Liberator was expected to field a 130-140 mm gun with a total vehicle weight in the range of 70 tonnes, which would have created a significant firepower and protection gap between the conjectural Liberator and the proposed NG-MBT. As a result, a new MBT development program, the 21st Century Main Battle Tank project, was established with new requirements once again stipulating a larger gun caliber.

By February 2003, the 140 mm L/50 T-22 and 155 mm L/46 T-23 guns had been selected as finalists and in September the 155 mm caliber was finally chosen as the new tank's armament. The 155 mm caliber was chosen in preference to the 140 mm caliber due to the greater ease with which guided munitions could be developed and better long-term growth potential. With the caliber selected, full-scale testing and evaluation began to develop the test gun into a production design and to produce a complete family of ammunition in the new caliber. The first tank prototypes were armed with a mixture of existing 120 mm T-17S guns and prototypes including the 140 mm T-22 and 155 mm T-23. The first pre-production variants of the T-23 were delivered in 2008 and integrated into the EMD testbeds for the newly-named HTA-02 Jaguar II with the first production guns integrated in March 2010. In 2009, the T-23 was officially type classified as the CBS-321 under the Millennium Inventory System.

Design

The smoothbore interior of the CBS-321.

The gun barrel is composed of high-strength alloy steel overwrapped by a tensioned carbon fiber material. The metal barrel is autofretted to improve resistance to stress corrosion cracking and wrapped with carbon fiber to improve strength and stiffness while reducing weight. This wrap replaces the older fiberglass wrap used in the T-17S smoothbore gun and is both lighter and stronger than the previous generation. As a result of its construction, the CBS-321 is rated to a maximum powder pressure of 880 MPa, greater than the 790 MPa of the newest T-17S barrels.

The carbon fiber wrap is the first combat application of such a design in a Carthaginian tank and has been carefully designed to not interfere with barrel cooling and thermal stresses when operating in situations requiring heavy and repeated fire. The barrel assembly is enclosed within a thermal sleeve to insulate the gun against external temperature variation and to reduce the gun barrel's infrared signature. In combat, the gun is usually further disguised through the use of IR camouflage netting.

Due to the higher flame temperature of the flashless triple-base propellant used in new rounds developed for the CBS-321, the barrel lining is composed of explosively bonded tantalum rather than conventional chromium, which would have resulted in an unacceptably high wear rate. The use of tantalum allows the gun to meet barrel life requirements, estimated at 1,500 effective full charges.

When firing a full-power charge, the CBS-321 recoils approximately 400 millimeters (16 in), an increase from the 280-millimeter (11 in) recoil of the T-17. The hydraulic recoil system was designed to maintain comparatively compact dimensions, being similar to the size of the 140 mm test gun. The system uses a hydraulic retarder and two pneumatic return cylinders to control the gun. A ten-slot muzzle brake is estimated to reduce recoil forces by up to 40% and make firing the gun more comfortable to crew within the tank. In order to stabilize the long barrel on the move, a tuned mass damper is mounted near the end of the gun just before the muzzle brake. The damper helps reduce vibrations and oscillations caused by motion in the vehicle and maintains accuracy while on the move.

Unlike the T-17 and the Russian 2A46, the CBS-321 does not feature a bore evacuator and instead relies on an automatic compressed air system to clear the barrel of fumes after firing. This system delivers greater reliability than a conventional passive fume extractor in clearing toxic fumes from the gun after firing and reduces the weight and bulk that must be stabilized as part of the gun system itself.

Variants

File:15cmtgun.jpg

140 mm demonstrator gun now on display at the Army Ordnance Museum.

• CBS-321

Standard Carthaginian production model manufactured by the Butare Army Arsenal and Philosir Precision Industries for use in domestically produced HTA-02 Jaguar IIs.

• Type 70

Standard Japanese production variant produced by the Kaohsiung Arsenal and Japan Steel Works for use in the Japanese-made Type 71 Se-Tsu variant of the HTA-02. The Type 70 has minor differences in breechblock dimensions and the recoil system but remains ballistically identical to the CBS-321 and is physically interchangeable between Carthaginian and Japanese tanks.

• M216

Export variant of the standard Carthaginian CBS-321 produced by Philosir Precision Industries and used in the Rhamosian M1A4V Jagdcheetah heavy tank destroyer.

Ammunition

The CBS-321 is designed to fire a variety of types of ammunition developed by the countries that operate the weapon, primarily armor-piercing fin-stabilized discarding-sabot rounds for anti-tank use and high-explosive (including HEAT) rounds against softer targets. While technology from the development of new rounds has generally been shared between Carthage and Japan, differences in expected employment of the Jaguar II led to different procurement decisions in regards to arming each nation's tank fleet.

Carthage

Several ammunition types used by the Carthaginian Army.

The ammunition types approved for use with the CBS-321 are a mix of both new designs and older types converted for use. The DSD-907 HEAT-AMP-T round was originally designed for the 140 mm TA-105W demonstrator and was converted for use in the CBS-321 through the use of a resized sabot. The DIT-910 APFSDS-T round was newly developed for the CBS-321 and based on a jacketed design trialed for the 120 mm T-17S smoothbore gun. In addition to the live rounds and their training counterparts, a dedicated pyrotechnic charge, the DTT-914, is also fielded for use during exercises.

• DSD-907 HEAT-AMP-T

The DSD-907 multi-purpose HEAT round is a tandem charge, programmable fuze munition designed for use against vehicles, helicopters, personnel, and fortifications. Designed with a depleted uranium liner and a larger fragmentation sleeve relative to previous models, the most significant performance improvement is the addition of the new smart fuze, which can be set to air burst, post-penetration, impact, and proximity detonation and which allows the DSD-907 to replace the previously separate canister, HEAT, and demolition rounds for a simpler ammunition load. Muzzle velocity is 1,400 m/s (4,600 ft/s) for an effective range of 3,000 m (3,300 yd). The DTD-912 MP-T is an inert training round designed to emulate the ballistics of the DSD-907.

• DIT-910 APFSDS-T

The DIT-910 is based around a 1,100-millimeter (43 in) depleted uranium penetrator designed for use against enemy tanks and other heavily armored vehicles. The penetrator is believed to use a steel jacket around the DU core to increase rigidity and resistance to bending, increasing effectiveness against composite armor arrays. Total cartridge weight is 45.5 kilograms (100 lb) and muzzle velocity is 1,675 m/s (5,500 ft/s) for an effective range of 4,500 m (4,900 yd). The DTT-913 TPCSDS-T is a training round with a steel core designed to match the ballistics of the DIT-910 with a range limited to 9,500 meters (10,400 yd).

• SGC-415 AATM-CE

The SGC-415 Advanced Autonomous Tank Munition-CE is a guided, tandem-charge HEAT weapon designed for medium to long-range engagements, including beyond-line-of-sight (BLOS) targets. The AATM-CE uses a dual-mode imaging infrared/semi-active laser seeker to enable fully autonomous engagement of targets beyond the tank's line of sight, while also allowing for man-in-the-loop guidance at BLOS ranges where the danger of collateral damage or friendly fire is too great for autonomous engagement.

• SGK-416 AATM-KE

The SGK-416 AATM-KE is a guided medium to long-range kinetic energy munition designed for use against main battle tanks and other heavily armored targets with extensive protection against HEAT munitions. While conceptually similar to the AATM-CE, the AATM-KE uses a depleted uranium penetrator for terminal effects and is guided by a dual-mode millimeter wave/semi-automatic laser seeker, enabling similar options for autonomous or man-in-the-loop guidance at ranges beyond 2,000 m (2,200 yd). Launch velocity is 1,200 m/s (3,900 ft/s) but impact velocity is 2,400 m/s (7,900 ft/s).

Japan

Live ammunition

• Type 69 HEAT-AMP-T

Domestic production designation for the DSD-907 HEAT-AMP round developed for the Carthaginian Army and used as the primary high-explosive round for the Japanese-produced Type 71. It is identical in performance and characteristics to the DSD-907.

• Type 68 APFSDS-T

The Type 68 is a conventional APFSDS round using a 940-millimeter (37 in) depleted uranium penetrator. The penetrator is believed to use a segmented design for improved penetration of the explosive reactive armor arrays commonly found on Taiping and Mongolian tanks. Total cartridge weight is 43.2 kilograms (95 lb) and muzzle velocity is 1,725 m/s (5,660 ft/s) for an effective range of 4,500 m (4,900 yd).

• Type 71 Canister

The Type 71 is a scaled up version of the Type 33 canister shell developed for the T-17 gun. It contains 2,400 tungsten balls designed to produce a shotgun-like effect to clear infantry and soft targets in the open. While the Carthaginian Army opted not to develop a domestic canister shell in favor of the airbursting DSD-907, the Imperial Japanese Army developed the round to break up ambushes and clear foliage in the dense jungles of Southeast Asia.

• Type 54M ATGM

The Type 54 is a semi-active laser homing gun-launched missile originally developed for the T-17 gun. The Type 54M variant is a modernized variant of the missile with a new warhead modified for use in the Type 71 gun with a sabot and larger propellant casing. Unlike the AATM series used by the Carthaginian Army, the Type 54 is subsonic and is powered throughout its flight. It is armed with a tandem-charge HEAT warhead.

Training ammunition

• Type 69 MTP-T

Local designation for the DTD-912 training round.

• Type 68 TPCSDS-T

The Type 68 is designed to emulate the ballistic performance of the Type 68 APFSDS-T round. Substantially similar to the DTT-913, is also cone-stabilized and intended for use in constrained training areas.

See also

Weapons of comparable role, type, and era

• 14.5cm PzK M-85 L/45
• M41