The US designated AT-11 (Russian Federation and Associated States (CIS) industrial designation 9K119 Svir guided weapon system, developed by the Tula KBP design Bureau for Instrument Building, includes the 125 mm 3UBK20 round with the 9M119M laser guided missile, IK13 tracker with built-in missile guidance laser channel and the 9S831 voltage converter.

The missile is fired from the 125 mm smoothbore gun installed in some versions of the T-72 including the T-72B and the export T-72S. It is understood that the system entered service around 1994.

The installation of this laser guided projectile enables targets to be engaged beyond the normal effective range of the 125 mm main armament of the tank. A typical load of Svir missiles wouid be six. Russian sources give the missile a hit probability of at least 80 per cent.

The missile is the same as used in the Refleks version, but the overall round weight is lighter indicating a reduced propellant charge. The system uses the coded laser guidance beam 1K13-49 sight assembly, which is fitted in place of the gunner's TPN-1-49 secondary night sight. The fire-control system is designated 1A40-1. The 4.2 kg HEAT warhead can penetrate up to 700 mm of armour.

The Svir operates on the same principles as those described for the Bastion (AT-10 'Stabber') family with the missile effectively riding in the centre of a laser funnel that is created by the 1K13 sight's laser emitter. The frequency of the beam is modulated in different sectors around the funnel so that if the missile deviates, the missile's onboard guidance system can detect the abnormal movement and correct the flight trajectory so that it moves back into the centre of the guidance beam. The guidance system uses a timer so that the laser funnel is periodically altered in diameter. This means that the missile effectively sees a relatively constant laser tunnel diameter as it moves along its flight trajectory.

First production 9M119M laser guided missiles had a single HEAT warhead but the latest versions have a tandem HEAT warhead to defeat targets fitted with explosive reactive armour.

In production. In service with the RFAS. Offered for export.

• T-72B MBT (125 mm gun/missile launcher - RFAS armies)

• T-72S MBT (125 mm gun/missile launcher - offered for export).