The Soviet 240 mm Mortar M240 is a 240 millimetres (9.4 in) breech loading smoothbore heavy mortar that fires a 130 kilograms (290 lb) projectile.
The mortar consists of a smooth-bored barrel with a breech and a breech-block frame, a frame with shock absorbers, mount with training and equilibrating mechanisms, a two-wheel traveling carriage with the suspension, a boom for changing from the firing to the traveling configuration, a baseplate and a towing bar with a lunette. The sights are carried separately and are mounted on the mortar only when firing. The shock absorbers are used to protect the sights from firing vibrations and also provide the link between the ordnance and the mount. It is also used when the mounting returns to the loading position after firing. The boom provides stability when firing and also has two winches to convert the mortar from the firing to the traveling configuration.
It is mounted on a wheeled carriage that supports the cradle and barrel much as in a conventional field gun. Unlike most other mortars, there is no bipod. The barrel is mounted at its centre of gravity in trunnions, which allow the barrel to be depressed to the horizontal for loading.
The M-240 has a minimum range of 800 m and a maximum range of 9,700 m. Traverse is limited to 18°, while elevation ranges from +45 to +65°. The sights, elevation and traverse gears are on the left side of the barrel. The mortar is normally towed, at a maximum speed of 40 km/h, muzzle first by an AT-P, AT-L or AT-S tractor, which also carries the 11-man crew. Additional vehicles carry the ammunition and emplacing equipment. On arrival at the firing position, which has to be on firm ground, the mortar is uncoupled from the tractor and the towing lunette is removed. The large circular welded baseplate is lowered to the ground and packed with earth to provide a stable firing platform.
The smoothbore barrel is 5.34 m (22.25 calibers) long and for loading is swung into the horizontal position. At the lower end of the barrel is the breech-block and projectile guide. Bringing the M-240 into action takes at least 25 minutes, slightly less to move it after firing. The weight in action is approximately 4,150 kg. The HE bomb weighs 130 kg, of which 34 kg is payload. The bomb, which is almost 1.5 m long, is brought to the mortar on a two-wheeled trolley and a team of five is used for loading. Large tongs/gripping pincers are used to lift the bomb from the trolley onto the projectile guide, with two men on each handle and the fifth steadying the fins. The bomb is then pushed into the barrel and the breech is closed. The barrel is then raised to the firing position. The rate of fire is about 1 rd/min.
As part of the 2S4 Tyulpan, the mortar is also used in a self-propelled configuration.