Crew A crew of five enlisted personnel operate the M252: the squad leader, the gunner, the assistant gunner, the first ammunition bearer, and the second ammunition bearer. • The squad leader stands directly behind the mortar where they can command and control their squad. In addition to having general oversight of all squad activities, they also supervise the emplacement, laying, and firing of the weapon. • The gunner stands to the left of the mortar where they can manipulate the sight, traversing handwheel, and elevating handwheel. They place firing data on the sight and lays the mortar for deflection and elevation. They make large deflection shifts by shifting the bipod assembly and keep the bubbles level during firing. • The assistant gunner stands to the right of the mortar, facing the barrel and ready to load. In addition to loading, they swab the bore after 10 rounds have been fired or after each fire mission. The assistant gunner is the person who actually fires the weapon. • The first ammunition bearer stands to the right rear of the mortar. They have the duty of preparing the ammunition (charge settings,
fuzes, etc...) and passing it to the assistant gunner. • The second ammunition bearer stands to the right rear of the mortar behind the first ammunition bearer. They maintain and keep a record of the ammunition in addition to the data corresponding to each fire mission. Their twofold records include a written table of firing data, type, and number of rounds fired, and the safety pins pulled from each round to provide physical evidence to the accuracy of the table. In addition they provide local security for the mortar position. File:Flickr - The U.S. Army - Securing Barge Matal.jpg|M252 mortar and crew in
Afghanistan, 2009 File:Defense.gov News Photo 081026-M-8774P-089.jpg|M252 mortar crew and ammunition in Afghanistan, 2008 File:24 MEU Deployment 2012, 81 mm mortars live fire 120731-M-KU932-058.jpg|Marines fire an M-252 81mm mortar during live-fire training at Udairi Range in Kuwait, 2012 File:US Marines Euphrates River Valley in Deir Ezzor province, Syria, Oct. 11, 2018.jpg|Marine M252 mortar crew deploying on a cliff-side in the Middle
Euphrates River Valley in
Syria, 11 October 2018
Types of rounds While the M252 does fire a weapon-specific series of ammunition, it can also fire rounds from the
M29 Mortar (only at charge 3 or below though). The M252 Mortar can fire the following principal classifications of training and service
ammunition: •
High explosive (HE): Designations M821, M821A1, M889, M889A1, M372-series, and M362. Used against personnel and light materiel targets. • M821A4 HE–Enhanced Fragmentation (HE–EF): is designed to satisfy
insensitive munition requirements while enhancing lethality, which is achieved by utilizing preformed
tungsten fragments. • Advanced Capability Extended Range Mortar (ACERM): Developmental guided round that adds wings, control fins, GPS navigation, a laser seeker, and an enhanced warhead; ACERM variations include a 120mm version with range, an 81mm extreme performance configuration with a range, a 5 inch
naval gun configuration, including other gun systems, and an air dropped
glide bomb version for delivery within a six times the altitude radius. •
Smoke Cartridge: Designations M819 and M375-series. Used as a screening, signaling, or marking munition. • Illumination (ILLUM) • VIS ILLUM. Designations M853A1 and M301-series. Used in night missions requiring illumination for assistance in observation. • IR ILLUM. Designation M816. Provides an aerial parachuting Infrared Illuminating round for use with Infrared Night Vision Equipment. • Non-Lethal Indirect Fire Munition: Developmental round based on the M853A1 that disperses
flash bang submunitions to temporarily daze people. • Practice (PRAC): Designations M880, M879, M68, and sabot. Used for training in limited areas. • Infrared Illumination (IR): Produces illumination which is only visible through the use of night vision devices.
Fuzes The M252 rounds have three
fuze types: the Multi-option Fuze (MOF)
M734, the Mechanical Time & Super Quick (MTSQ) M772 and the Point-Detonating (PD) Fuze M935. The M734 is used for the M720 HE round and can be set to function as proximity burst, near-surface burst, impact burst, or delay burst, the M772 is used for the IR & VIS ILLUM (M816, M853A1) to activate the Illum candle during the rounds height point of its trajectory; the elevation and charge will determine the time set on the fuze.
Method of propulsion The range of a mortar is controlled by the number of
propellant charges attached to the tail of the mortar designated M223. A charge is a semi-circular donut of nitrocellulose, which resembles a "
horseshoe". A round for the M252 mortar comes with four charges attached. Longer-range shots require more propellant than can fit in the tail of the round, hence the necessity of external charges. When the target is ranged, a mortar team member adjusts the amount of propellant by removing horseshoe charges from the projectile. The mortar squad leader verifies the number of charges; then the assistant gunner drops the round down the muzzle of the tube. The round, pulled by gravity, accelerates down the smooth bore of the mortar until the
primer (in the base of the tail boom of the round) strikes the
firing pin located in the bottom of the mortar tail assembly. The primer detonates, igniting the charge in the tail fin, which in turn ignites the horseshoes charges on the round. The charges
deflagrate, releasing hot, expanding gas which pushes against the round with the
obturating ring on the projectile, sealing the gas behind the projectile. The pressure from the expanding gas accelerates the projectile until it leaves the end of the tube. ==Operators==