Two different versions of the Growler were developed; the M1161 light strike vehicle (LSV), and the M1163 prime mover variant as part of the
Expeditionary Fire Support System (EFSS) towed heavy 120 mm mortar. A number of the separate 36-round ammunition trailers, the M1162, were ordered, but further design was dropped and its duties to carry the 35 lb mortar shells were incorporated into the M1163 Prime Mover. The M1161 LSV variant is armed with either an
M2HB .50cal BMG machine gun,
M240G 7.62mm MG or
Mk19 40 mm automatic grenade launcher. The 120 mm mortar towed by the M1163 Prime Mover is the French
RT-120, deployed by United States forces as the
M327 Dragon Fire. The Growler's central role of cross-country scout and aerially-deployed forward unit has led to further modifications, including use of the rifled precision extended range munition (PERM) system. towed 120mm heavy mortar and M1163 Growler back into an
Osprey on board . On November 10, 2004, the
Marine Corps Systems Command (MCSC) awarded
indefinite-delivery, indefinite-quantity contract M67854-05-D-6014 with
firm-fixed-price and cost-plus-award-fee contract line-item numbers for a base year and up to six option years to
General Dynamics Ordnance and Tactical Systems (GDOTS) for $12,057,159 for procurement of 66 EFSSs and up to 650 ITVs. The MCSC selected GDOTS over two other offerors. On September 20, 2007, Senator
Carl Levin, Chairman of the Senate Committee on Armed Services filed a protest on behalf of a constituent, Rae-Beck Automotive, LLC, a subcontractor to one of the losing offerors. The
DOD inspector general's audit did not substantiate most of the constituent’s concerns, but did note concerns with the MCSC program management and contract award for the EFSS and ITV programs. ’s
Force Reconnaissance Detachment in Djibouti, 2015. By 2008, unit cost had risen by 120%, leaving each Growler scout variant with a cost of $209,000 per unit. The prime mover mortar contract price rose by 86%, to $1,078,000 cost per unit. Problems with M1161 and M1163's throttle system were identified in May 2012 following an accident at
MCB Camp Pendleton, California. The entire vehicle fleet was grounded, pending repair. During
RIMPAC 2014, the Marines fitted a Growler ITV with Torc Robotics' Ground Unmanned Support Surrogate (GUSS) system, turning it into an
unmanned ground vehicle. The GUSS system's aim is to lighten troops' loads by carrying up to of equipment; it can also serve as an unmanned medical evacuation vehicle. A GUSS-equipped ITV can autonomously follow a person wearing a beacon at a predetermined distance while cruising at up to . A Marine can take direct control of the vehicle through a robotic controller or switch it to manual operation and drive it themselves if needed. The unmanned ITV may be fielded within five years. ==Replacement==