RFSS is lightweight 6x6 Ranger Fire Support System.

The system started life as a basic, manually launched version of BAE Systems' M326 120 mm mortar mounted on the back of a 4x4 Ranger vehicle, but the army requested that the mortar be fitted with its associated digital fire-control system (FCS) and automated setup system, which exceeded the 1,000-lb (454-kg) payload of the 4x4 vehicle, hence its migration to a 6x6 platform with its 1,625-lb payload.

The lightweight manual deployment system was recently tested during live firing at Fort Campbell for the US Army's product manager for Guided Precision Munitions and Mortar Systems, but crews preferred the automated system.

As a result, the latest RFSS version uses essentially the same fixtures and launching system as the in-service trailer-mounted weapon, but removes the need for a prime mover. The 6x6 Ranger platform has a high degree of cross-country mobility and can travel at speeds of up to 40 mph.