The incentive to design a lightweight 120 mm smoothbore gun evolved from the need to retrofit the Swiss Army Pz 68 MBTs at present armed with a 105 mm rifled gun with Royal Ordnance L7 ballistics.

The available 120 mm guns would not fit into the relatively small Pz 68 turret, no extensive turret modifications were allowed and a moderate trunnion load was required. For interoperability reasons the 120 mm gun was required to fire the same ammunition as the Swiss Leopard 2 MBT.

To meet this requirement the 120 mm Compact Tank Gun (CTG) was designed by SW Swiss Ordnance Enterprise Corporation.

To keep the dimensions as small as possible a high strength steel was used with a 1,300 N/mm2 yield strength. This was tested for fracture toughness and machinability before the prototype barrels were manufactured.

The 120 mm ordnance has been fitted with a semiautomatic vertically sliding wedge breech block with electrical firing. Two recoil brakes and one recuperator are fitted.

The 120 mm smoothbore gun of the Leopard 2 is of 44 calibres in length whereas the new 120 mm gun is an L/49. The front end of the barrel has a dovetail attachment for fixing a muzzle reference system while the bore evacuator is a filament wound glassfibre composite.

It has been designed to fire current and projected 120 mm smoothbore rounds and has a barrel fatigue life of 1,000 rounds.

Although designed for installation in the Swiss Pz 68, it is suitable for upgrading other existing MBTs armed with 105 mm guns.

Firing trials carried out at a range of 1,150 m with 10 rounds of APFSDS ammunition give the following dispersion pattern:

Standard deviation

Elevation s = 0.21 mils

Azimuth s = 0.14 mils.

Although trials have so far been carried out on a Pz 68 MBT, with the installation of a suitable muzzle brake the 120 mm Compact Tank Gun can also be fitted to lighter combat vehicles in the 25 to 30 tonne class.

Early in 1998, a version of the Compact Tank Gun fitted with a muzzle brake was installed in a new three person Hagglunds turret installed on a modified Hagglunds Vehicle CV 90 tracked chassis. This started its firing trials late in 1999.

Early in 1999, it was revealed that the Jordanian King Hussien Main Workshops and the SW Swiss Ordnance Enterprise Corporation had completed the prototype of a US supplied M60A1 Main Battle Tank (MBT), with its original 105 mm M68 rifled tank gun replaced by the SW Swiss Ordnance Enterprise Corporation 120 mm smoothbore Compact Tank Gun (CTG).

The M60A1 turret was sent to the SW Ordnance Enterprise Corporation facility at Thun where the new 120 mm CTG gun was fitted. The complete turret was then sent back to Jordan and integrated onto the M60A1 MBT chassis at the King Hussein Main Workshops.

Following its public showing at IDEX 99 in the United Arab elements the vehicle returned to Jordan. Firing trials of the upgraded M60A1 MBT are expected to take place in Jordan in 1999.

A second M60A1 MBT with the 120 mm CTG is expected to be completed late in 1999. This programme was still in its early stages with no funded production programme yet established.

Development complete. Trialled and installed in Pz 68, CV 90120 and M60A1.