AMOS or Advanced Mortar System is a 120 mm automatic twin barrelled, breech loaded mortar turret. AMOS has been fitted to a wide range of armoured vehicles such as the Sisu Pasi, Patria AMV and Combat Vehicle 90. The Swedish Navy originally planned to fit AMOS to the CB90 assault craft, but found the ship too small to carry it. Instead a project to develop the larger Combat Boat 2010 was launched specifically to carry AMOS.

When fitted to a vehicle, both GPS- and inertia positioning are used. The electronic fire-control system utilises digital maps. Twin barrelled AMOS is able to keep up rate of fire of 12 rounds per minute. Using its computer controlled MRSI feature (multiple rounds simultaneous impact) it is possible to set upon a burst of up to 16 rounds that hit the target simultaneously. The first rounds are fired at higher angles with more propellant so that the rounds fly in a high arc. The next rounds are shot later with a slightly smaller angle and less propellant so that they fly a lower arc to the same target. This can be done seven times in a row, always adjusting the angle and power. The adjustment between shots is done by a computer. The strike of one AMOS unit roughly equals one strike of an artillery battery.

An AMOS turret has a full 360-degree field of fire at elevations between -3 to +85 degrees. AMOS is capable of both conventional indirect fire and direct fire for self-protection. In a typical installation—mounted on a Patria AMV or a similar vehicle, the vehicle can dash to the next position roughly 30 seconds after initiating the 14-round salvo, leaving minimal time for detection and counter-attack by enemy; evasion is the primary means of self-protection.

AMOS is manufactured and marketed by Finnish/Swedish Patria Hägglunds, a joint venture between Finnish Patria and Swedish BAE Systems Hägglunds. The system is known as the SSG120 in Swedish service. Ammunition for AMOS includes the Strix guided round and a modification of the Spanish Instalaza 120 mm Mortar Cargo Round "MAT-120" (although the latter are restricted to Finnish inventory and are slated for decommissioning due to their contravention of international treaty). Because AMOS is breech-loading, it cannot fire standard muzzle-loaded mortar rounds. AMOS rounds feature a 'short stub case' at the base of the fins, similar to a sabot. In this way, expended rounds fired by AMOS can be easily differentiated from traditional mortar systems.