60mm HVMS

The 60mm HVMS (High Velocity Medium Support) gun is a self-loading autocannon jointly developed by IMI Systems of Israel and OTO Melara of Italy. It was designed to be mounted on light armoured vehicles to provide an anti-armour capability using high-velocity sub-calibre kinetic ammunition.

Overview
The 60mm HVMS autocannon was designed as an infantry support gun mounted on light armored vehicles.

The project commenced in 1977, originally as a joint development between IMI Systems of Israel and OTO Melara of Italy, whereby IMI Systems were expected to develop the gun and ammunition, and OTO Melara the autoloader and a lightweight two-man turret which could be mounted on a variety of different armored fighting vehicles (AFV). However, both companies went their own way developing their own versions, although each retained the same cartridge case dimensions. The IMI Systems version is known as the High-Velocity Medium Support (HVMS) gun, while the OTO Melara version is known as the High Velocity Gun System (HVGS).

Despite being judged a success by IMI Systems, the gun did not enter service with Israel, and the only export sale was in 1983 to Chile to upgrade M24 Chaffee and M50 Super Sherman tanks. OTO Melara's version was proposed for fitment to a variant of the Italian Army's Dardo infantry fighting vehicle (which the company co-developed with Iveco), but as of 2021, this proposal has not eventuated.

Design
The gun features a barrel with a bore of 60 mm and a length of 70 calibers (4.2 metres), with a fume extractor approximately halfway down its length. The barrel is fabricated using the autofrettage method to allow the wall to be thin but extremely strong. A hydro-spring recoil system employs a spring surrounding the breach-end of the barrel which is protected by a shroud and a truncated rubber sleeve, allowing quick barrel changes as the gun and recoil system can be removed/installed as a single unit.

Although originally designed with an automatic loading system, the gun can also be manually loaded. The automatic loader is recoil-operated and features a vertical magazine with capacity differing between the IMI Systems and OTO Melara versions. Rounds can be fired individually or in a three-round burst, or in the case of the OTO Melera version, in full automatic with a maximum rate of fire of 30 rounds per minute. Manual loading consists of the traditional method of inserting the shells into the vertically-sliding breach by hand, augmented by hydraulic assistance. Manually loaded, the rate of fire is up to 12 rounds per minute with a reloading time of three seconds between firings. Firing is by an electrically-actuated system.

The gun was originally designed to be installed in the T60/70 turret, a lightweight two-man turret which also contained a 7.62mm machine gun and four electronically-operated smoke dischargers mounted on each side. The turret could be fitted to a number of light armoured vehicles, and was trialled by the IDF on the M113 armoured personnel carrier, and by Italy in the Fiat Type 6616 4x4 armoured car. However, this turret was not produced and any operational vehicles which received the gun, such as those of the Chilean Army, had it fitted to existing turrets modified accordingly.

The gun can fire both armour-piercing fin-stabilised discarding sabot -tracer (APFSDS-T) and high explosive (HE) 60x640R ammunition. An inert training round is also available.

Performance
For testing, the gun was fitted to a British QF 6-pounder gun carriage and fired against static Russian T-62 range targets.

The APFSDS-T ammunition was capable of penetrating 120 mm of rolled homogeneous armour sloped at 60 degrees at a range of 2 km. Rounds were measured leaving the barrel travelling at 5,300 ft/s, losing only 300 ft/s after the first kilometer of travel. The rounds were able to penetrate the armor of a T-62 from any angle as well as the side armor (15 – thick) of two T-62s arranged side-by-side at 2,000 m and was highly accurate at distances of over 2500 m. This performance bettered that of APDS rounds fired from the Royal Ordnance L7 105 mm gun.

Vehicles fitted with the gun
The gun was mounted on the following vehicles in either a prototype or demonstration, or operational capacity:


 * B1 Centauro wheeled tank destroyer (prototype only)
 * BWP-2000 infantry fighting vehicle (prototype only)
 * Dardo infantry fighting vehicle / C13-60 light tank / VCC-80 (prototype only)
 * Fiat Type 6616 armoured car (prototype only)
 * M24 Chaffee light tank
 * M41 Walker Bulldog light tank
 * M-60 Sherman medium tank
 * Marder infantry fighting vehicle (prototype only)
 * M113 armoured personnel carrier (prototype only)
 * MOWAG Piranha IB 6×6 wheeled infantry fighting vehicle (prototype only)
 * VBM Freccia wheeled infantry fighting vehicle (prototype only)

Operators

 * 🇨🇱Chilean Army: In 1983, the 60mm HVMS was fitted to M24 Chaffee and M-50 Sherman tanks, which were known at the time, as the M-60 Sherman tanks. It is believed that when the M24 Chaffee's were withdrawn from service in the early 2000s. The 60mm HVMS autocannons was fitted to one prototype M41 Walker Bulldog and one prototype Piranha 6x6 IFV that was trialed. As of 2022, it is uncertain as to whether any vehicles armed with this autocannon remain in active service.

Ammunition
The following specifications are for APFSDS-T ammunition:
 * weight:
 * complete round: 6 kg
 * projectile: 1.35 kg
 * sub-projectile: 870 g
 * length:
 * complete round: 620 mm
 * projectile: 292 mm
 * sub-projectile diameter: 17 mm
 * muzzle velocity: 1620 m/s

The following specifications are for HE ammunition:
 * weight:
 * complete round: 7.2 kg
 * projectile: 2.9 kg
 * length: 640 mm
 * muzzle velocity: 815 m/s
 * fuse: point detonating, base detonating, proximity, and delayed

Gun
The following specifications are for the gun assembly (i.e. barrel and breech), less mounts:
 * bore: 60mm
 * calibers: 70
 * length: 4.2 m
 * weight:
 * IMI Systems: 700 kg
 * OTO Melara: 1000 kg
 * recoil system: hydro-spring
 * recoil force: 9000 kg
 * recoil travel: 270 mm
 * rifling: right hand, 22 grooves, 1 in 30 turns per calibres
 * firing: electrical
 * firing modes: single shot, burst, full auto
 * max. rate of fire: 30 rounds per minute

Turret
The following specifications are for the T60/70 turret originally designed to house the gun:


 * material: aluminium
 * length: 6.165 m
 * width: 2.1 m
 * height above turret ring: 661 mm
 * depth below turret ring: 1162 mm
 * weight:
 * without gun: 2200 kg
 * fitted and loaded: 5000 kg
 * elevation: electrically operated, -6 to +50 degrees
 * traverse: electrically operated, 360 degrees
 * sight magnifications:
 * gunner's: x8
 * commander's: x2.5, x10
 * power supply: 24V
 * crew: 2

A manual version (i.e. non-electrically operated) was also made available.