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M121, 120mm Battalion Mortar System (BMS)

The M121 120mm Battalion Mortar System (BMS) provides close-in and continuous indirect fire support to maneuver forces and can rapidly respond to the threat. This mortar system is being fielded to mechanical infantry and armored units. The M121 will give rapid shoot and scoot support to the infantry forces. The M121 Mortar is mounted in a M1064 Armored Personnel Carrier (M113 family of vehicles) and will replace, one for one, the 4.2" Mortar. provides The M121,along with its associated family of ammo, increases range, lethality, smoke obscuration effectiveness and improves safety over the M30 4.2 inch mortar, along with improved reliability and safety.

The M121 Mortar System consists of the following major components: With the use of an auxiliary M9 Baseplate and extension feet for the M191 Bipod, the M121 can be dismounted from the vehicle and emplaced for ground-mounted operation. Ammunition racks installed in the M1064 can accomodate 69 rounds of 120mm mortar ammunition.

The M-120 mortar, when fired, especially in the carrier configuration, produces a blast overpressure (impulse noise level) in excess of the allowable limits. Operators subjected to this blast overpressure could have suffered permanent hearing loss if this health hazard had not been identified. The health hazard assessment performed on this system recommended that

When firing in the carrier-mounted mode, a Blast Attenuation Device (BAD) is attached to the muzzle of the M298 cannon to reduce the blast effects on the mortar crew.


Maximum Range..........7200 meters
Minimum Range..........200 meters
Maximum Rate of Fire.........16 rounds/min (first minute)
Sustained Rate of Fire..........4 rounds/min

Contractor: Watervliet Arsenal
Procurement Type: Production
Previous Contracts: 5
Contract Type: Firm Fixed Price
Production Qty: 110
Scope: Full Scale Production

In 1988 Product Manager for Mortar Systems, selected Lockheed Martin Ordnance Systems as the research and development and initial production prime contractor for the 120mm mortar and ammunition. Lockheed Martin teamed with Soltam Limited of Israel in the Non-Developmental Item acquisition. Subsequently, the U.S. Army awarded Watervliet Arsenal all weapon production under the Arsenal Act competition with Martin Marietta.

Other key contractors and government facilities for this program are: Chamberlain Manufacturing Corporation of Scranton, Pa.; Loral Corporation of Archibald, Pa.; Armtec Corporation of Coachella, Calif.; Hercules Inc of Radford, Va.; Lockheed Martin Ordnance Systems at Milan Army Ammunition Plant of Milan, Tenn.; Red River Army Depot of Texarkana, Texas; Anniston Army Depot of Anniston, Ala.; and the Product Manager for the M113/M60 Family of Vehicles of Warren, Mich.

Approximately 1,191 M1064 carriers will be converted to the M121 BMS systems and 1,191 M121 mortas will be produced at a total cost of $108 million. Conversion ran to June 1998, and production of the M121 mortar ended in October 1996. Future enhancements to the system include an improved sight unit, improved smoke round, conventional and infrared illumination rounds, a full range training round and the M30 mortar ballistic computer. Proposed long-term enhancements include extended range precision guided munitions and a digital fire control system.

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Maintained by Robert Sherman
Originally created by John Pike
Updated Tuesday, February 22, 2000 10:15:37 AM