Yugoimport SDPR of Serbia and Montenegro is marketing a number of artillery upgrades including one for the 105 mm M56 towed howitzer, which was originally designed and built in the former Yugoslavia many years ago.

In addition to being used in large quantities by Yugoslavia, it was exported to a number of countries including Cyprus, El Salvador, Guatemala, Indonesia and Mexico.

Development of this upgrade package is complete and production can commence as soon as orders are placed. The upgraded system is called the 105 mm howitzer M56-2 or M56A1. As of early 2008, it is understood that this upgrade remained at the prototype stage.

The standard production 105 mm M56 howitzer is fitted with a 105 mm/28 calibre ordnance. The upgraded M56-2 model has a longer 105 mm/33 calibre barrel, which is also made of stronger steel and therefore allows 105 mm projectiles to be fired with a higher charge and therefore a longer range.

The original barrel assembly weighed 526 kg while the new 105 mm/33 calibre barrel weighs 616 kg with the barrel on its own weighing 410 kg. Other modifications include the installation of a new double-baffle muzzle brake while the existing horizontal sliding breech and breech block are replaced by identical ones made of stronger steel.

In addition there have been minor modifications of the existing pneumatic equilibrator with the pressure being increased in order to compensate for the added weight of the new 105 mm barrel assembly. The standard split trails have been retained but additional mass has been fitted to each trail.

The 105 mm M56-2 can fire the older US developed 105 mm M1 high-explosive (HE) projectile out to a maximum range of 11,800 m but increased range and effectiveness is achieved with the use of the new generation of higher performance 105 mm ammunition.

The new locally developed 105 mm HE-ER (High-Explosive Extended Range) projectile with a base-bleed unit attached can achieve a maximum range of 18 km with a muzzle velocity of 675 m/s.

It can also fire the new HE-ER Boat Tail (BT) projectile, which has a maximum range of 15 km and a muzzle velocity of 675 m/s.

According to Yugoimport, maximum rate of fire is eight rounds per minute and the barrel has a life of 10,000 equivalent full charge (EFC) rounds.

Yugoimport has also developed a new self-propelled (SP) model of the upgraded M56A-2 towed howitzer mounted on the rear of a modified locally produced FAP 1117BS/AV (4 × 4) forward cross-country truck chassis. As far as it is known this remains at the prototype stage.