The 105 mm barrel assembly of the Model 56 Pack Howitzer is composed of the barrel, breech ring, slipper and muzzle brake. The weapon has a multibaffle muzzle brake. The vertical sliding breech block has a percussion firing mechanism which can be cocked automatically or by hand. Firing is either by hand lever or by lanyard.The gun carriage comprises the undercarriage, saddle, cradle, upper and lower recoil systems, two balancing springs, two sights and the shield.
The undercarriage consists of a cross head housing the saddle centre pivot pin, two stub-axles, spring equalising rocker arm and two articulated arms. Each of the stub-axle supporting arms has two bearings into which the stub-axle can be fitted, this carries the wheel assembly and its handbrake. Each of the articulating brackets carries a trail leg of two or three sections, which can be folded up and interlocked. The end section of the trail may be anchored to the ground by a knife or rock spade.
The capability of this weapon to be "knocked-down" allows the sections to be transported a number of ways although the original design was for mule-pack using special pack saddles. More usually it is towed by a light vehicle such as a jeep or Land Rover, and with the shield removed it can be carried inside a M113 APC. However, its particular attraction to Western Armies in the 1960s was its light weight meant it could be lifted in one piece by helicopter.
This made the gun popular with light artillery units in many countries as well as the more specialised Mountain and Airborne troops. Over all, the Mod 56 has served in more than 30 countries worldwide, of which a partial listing of the major operators is listed below. It can be used either as an artillery gun using indirect fire ballistic trajectory or as anti-tank weapon using line-of-sight fire. OTO Melara designed this gun to be fully compatible with the charges and projectiles employed on the US Army M101 105mm howitzer.