The precursor of the M1129, the MCV-A, carried a mortar that could only be used dismounted, whereas the M1129B is only capable of firing its weapon from the mounted position within the vehicle.

The M1129 is used in the US Army Stryker brigade combat teams, where it is part of each Brigade's maneuver infantry battalion's and reconnaissance, surveillance and target acquisition (RSTA) squadron's modified table of organization and equipment (MTOE).

The RSTA squadron only receives the 120 mm mounted mortar, there is no augmentation dismounted maneuvers.

Each Stryker infantry battalion thus has a total number of 10 mortar carriers, all of which are equipped with the 120 mm system.

Each Stryker RSTA battalion has a total of 6 mortar carriers, all of which are also equipped with the 120 mm system.