M252 mortar

The M252 81 mm medium weight mortar is a British-designed smooth bore, muzzle-loading, high-angle-of-fire weapon used for long-range indirect fire support to light infantry, air assault, and airborne units across the entire front of a battalion zone of influence. In the U.S. Army and U.S. Marine Corps, it is normally deployed in the mortar platoon of an infantry battalion.

M252
M252 mortar
TypeMortar
Place of originUnited Kingdom (designed)
United States (manufactured)
Service history
In service1987–present (United States)[1]
Used bySee Operators
WarsVietnam War (prototype model)
Soviet–Afghan War
Gulf War
War in Afghanistan
Iraq War
Syrian Civil War
Specifications
Mass41.3 kilograms (91 lb)
Length50 in (127 cm)
Barrel length1.27 metres (4 ft 2 in)
Crew5
Caliber81 millimetres (3.2 in)
Elevation45°–85.2°
Traverse5.6°
Rate of fire8–16 rpm sustained
20–30 rpm in exceptional circumstances and for short periods
Effective firing rangeHE: 91–5,935 m
(99–6,490.6 yd)[1]
Feed systemmuzzle-loaded

Design
Mortar team carrying (L-R) the mount, the baseplate and sight, and the cannon for an M252A2 system

The M252 system weighs 91 lb (41 kg) completely assembled and is composed of the M253 Cannon (35 lb, 16 kg), M177 Mount (27 lb, 12 kg), M3A1 Baseplate (29 lb, 13 kg), and the M64A1 Sight Unit (2.5 lb, 1.1 kg).[1] The mount consists of a base plate and a bipod, which is provided with screw type elevating and traversing mechanisms to elevate/traverse the mortar. The M64A1 sight unit (also used on the M224) is attached to the bipod mount. The M252 is a gravity-fired smoothbore system. Attached to the muzzle of the weapon is the Blast Attenuation Device (BAD), used to reduce the blast effects on the mortar crew. To increase cooling efficiency, the breech end is finned; though first-hand accounts attest that the level of cooling is negligible. The cannon also has a crew-removable breech plug and firing pin.

High explosive rounds fired by the M252 weigh 10 lb (4.5 kg) and can have an effective kill radius of 35 m (115 ft).[2]

In 2017, the Marines revealed they were developing precision-guided rounds for the 81 mm mortar, similar to efforts for the 120 mm Expeditionary Fire Support System but in a man-portable system.[3]

History

The M252 is an adaptation of the British 81mm L16A2 mortar developed in the 1950s.[4] It entered service with the U.S. Army and replaced the previous 81 mm M29 mortar in 1987. It was adopted due to the extended range (from 4,500 meters to 5,650 meters) and enhanced lethality. In the U.S. it is produced by Watervliet Arsenal.

Lighter, M252A2 version

A lightweight version, the M252A1 was first fielded in December 2014. By using lightweight materials such as aluminum, titanium and nylon kevlar the total weight was reduced by 12 pounds (5.4 kg) to 79 pounds (36 kg).[4] The M252A1 also required less maintenance with its internal gears greaseless.[4] The M252A1 was scheduled to replace the M252 in 2016.[4][5] In November 2016, the Watervliet Arsenal received a contract to produce the bipods which have an "A" shaped bipod frame with deliveries to be completed by March 2020.[6][4][5] As part of the same program, a lightweight version of the M224 60mm mortar the M224A1 was also developed.[4][7] The Marines developed an improved M252A2 version that weighs about 8.16 kg (18 pounds) less than the original and incorporates a 4× magnification sight with a new cooling system.[8]

Operation

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.

  1. 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.
  2. 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.
  3. 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.
  4. 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.
  5. 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.
  • M252 mortar and crew in Afghanistan, 2009
    M252 mortar and crew in Afghanistan, 2009
  • M252 mortar crew and ammunition in Afghanistan, 2008
    M252 mortar crew and ammunition in Afghanistan, 2008
  • Marines fire an M-252 81mm mortar during live-fire training at Udairi Range in Kuwait, 2012
    Marines fire an M-252 81mm mortar during live-fire training at Udairi Range in Kuwait, 2012
  • Marine M252 mortar crew deploying on a cliff-side in the Middle Euphrates River Valley in Syria, 11 October 2018
    Marine M252 mortar crew deploying on a cliff-side in the Middle Euphrates River Valley in Syria, 11 October 2018

Types of rounds
Three 81mm M29 Mortar rounds, M374A2 (High Explosive), M375A2 (White Phosphorus), and M301A3 (Illumination).

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:[9]

  • High explosive (HE): Designations M821, M821A1, M889, M889A1, M372-series, and M362. Used against personnel and light materiel targets.
    • Advanced Capability Extended Range Mortar (ACERM): Developmental guided round that adds wings, control fins, GPS navigation, a laser seeker, and an enhanced warhead;[2] increases accuracy to within one meter and can reach a range of 20 km (12 mi) in five minutes.[10] ACERM variations include a 120mm version with 24-33km range, an 81mm extreme performance configuration with a 40 to 60km range, a naval configuration for 5 inch and other gun systems, and an air dropped glide version for delivery within a six times the altitude radius.[11]
  • Smoke Cartridge: Designations M819 and M375-series. Used as a screening, signaling, or marking munition.[12]
  • Illumination (ILLUM): Designations M853A1 and M301-series. Used in night missions requiring illumination for assistance in observation.
    • Non-Lethal Indirect Fire Munition: Developmental round based on the M853A1 that disperses flash bang submunitions to temporarily daze people.[13][14]
  • Training practice (TP): 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 M224 rounds have two fuze types: the Multi-option Fuze (M734) and the Point-Detonating 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.

Method of propulsion
Round with the standard four C-charges

The range of a mortar is controlled by the number of propellant "C-charges" attached. A charge is a semi-circular donut of nitrocellulose, which resembles a puffy letter "C." 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, the first assistant ammunition bearer adjusts the amount of propellant by removing C-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 tube. The primer detonates, igniting the charge in the tail fin, which in turn ignites the C-charges on the round. The C-charges ignite, releasing hot, expanding gas which pushes against 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
Map with M252 operators in blue.

Current operators

See also

References
  1. "Fact File: M252A1 Mortar". U.S. Army. Archived from the original on 23 November 2012. Retrieved 15 October 2017.
  2. Hambling, David (2 June 2016). "The Marines' Trusty Mortar Is Getting a Major Upgrade". Popular Mechanics. Archived from the original on 16 October 2017. Retrieved 15 October 2017.
  3. Marines Want a Truck-Mounted Rocket-Launcher that Fits in an Osprey Archived 29 October 2017 at the Wayback Machine - Defensetech.org, 26 October 2017
  4. Calloway, Audra (11 December 2014). "Picatinny lightens Soldiers' load, shaves 12 pounds off mortar system". US Army (Press release). Picatinny Public Affairs. Retrieved 5 October 2021.
  5. "U.S. Army Weapon Systems Handbook 2018" (PDF). United States Army Acquisition Support Center. p. 324. Retrieved 5 October 2021.
  6. Snyder, John B (29 November 2016). "Army awards $8.5M contract to Watervliet Arsenal to lighten the load for infantrymen, Marines". US Army (Press release). Watervliet Arsenal Public Affairs. Retrieved 5 October 2021.
  7. Baddeley, Adam (June 2011). "Mortars and Ammo". Ground Combat Technology. Vol. 2, no. 2. Archived from the original on 28 March 2012.
  8. Schehl, Matthew L. (7 December 2015). "Marines get new mortar in Iraq to protect base from IS". Military Times. Archived from the original on 1 May 2016. Retrieved 15 October 2017.
  9. "81mm Mortar Ammunition And Fuzes". Gary's U.S. Infantry Weapons Reference Guide. 10 May 2006. Archived from the original on 11 June 2012. Retrieved 10 June 2012.
  10. Marines In the Hunt for a Mortar Round That Can Fire Up to 12 Miles Archived 22 April 2018 at the Wayback Machine. Military.com/Kitup. 18 April 2018.
  11. https://ndiastorage.blob.core.usgovcloudapi.net/ndia/2016/armament/18279_Steelman.pdf
  12. Pike, John. "M819 81mm Smoke Cartridge". Globalsecurity.org. Archived from the original on 19 March 2017. Retrieved 15 October 2017.
  13. Sanborn, James K. (6 December 2014). "Marines, soldiers could soon carry 'flash bang' mortars". Marine Corps Times. Archived from the original on 8 July 2017. Retrieved 15 October 2017.
  14. Sanborn, James K. (24 December 2014). "Need to know, 2015: What's new in gear and uniforms". Marine Corps Times. Archived from the original on 8 July 2017. Retrieved 15 October 2017.
  15. Iraq: Turning a blind eye: The arming of the Popular Mobilization Units (PDF) (Report). Amnesty International. 5 January 2017. p. 26. MDE 14/5386/2017. Archived (PDF) from the original on 13 March 2017. Retrieved 26 October 2018.
  16. Dillon, Louis (15 July 2019). "Army prepares for rollout of new handheld mortar computers". Defence Connect. Retrieved 25 August 2019.
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