The 81-mm mortar, M252, is a smooth-bore, muzzle-loaded, high-angle-of-fire weapon. They are fuzed with the M524-series, M256-series, or M532. The fuze setter, M25, sets M84-series time fuzes. The fuze body is graduated from 0 to 50 seconds in 2-second intervals; 10-second intervals are indicated by bosses. a. M252 81mm Mortars The M252 81mm medium extended range mortar (see diagram below) is a crew-served, smooth bore, muzzle loaded, high angle of fire weapon system. Both legs are fitted with a disk-shaped foot with a spike beneath to prevent the mount from slipping. This may preclude moving the bipod. (703) 614-3727, Office of the Chief Information Officer The components of the mortar consist of a cannon, mount, and baseplate. The cartridge uses the M218 propelling charge, which consists of four horseshoe-shaped increments fitted around the tail. The gunner moves the mortar as the assistant gunner steadies it. The elevation change announced must be less than 90 mils and more than 35 mils. c. The assistant gunner stands to the right of the mortar, facing the barrel and ready to load. There must not be a visible gap between the fuze and cartridge body. The safety pull wire is removed just before inserting the cartridge into the mortar. Cartridges assembled with the M524 (A1, A2, A3, or A4) fuze are for use by the U.S. Marine Corps and U.S. Navy only. FT 81-AI-3 Firing Tables Mortar, 81mm: M28A1 and M29 Mortar 81mm Self propelled M125A1 and M125 Carrier, 81mm Mortar Tracked XM755 (1) The M772A1 fuze is a MTSQ. It is constructed from ductile cast iron and contains about 1.5 pounds of cyclonite (RDX)/trinitrotoluene (TNT) composition explosive. However, at temperatures above 32 degrees Fahrenheit and at angles greater than 1068 mils, the flight time is sufficient to permit arming. Table 4-3. It comes preset to function on SQ/IMP, and the selector slot should align with the SQ mark on the ogive. Each cartridge weighs about 10 pounds and is provided with the M223 propelling charge, consisting of four horseshoe-shaped increments fitted around the tail. The mortar is within two turns of center of traverse. News. After the bands are broken and the box opened, the rounds should be removed by allowing them to roll out along the lid of the box (Figure 4-8). He may assist the gunner in shifting the mortar when the gunner is making large deflection changes. LARGE DEFLECTION AND ELEVATION CHANGES. The propelling charge consists of an ignition cartridge and removable propellant increments. The M252 is highly accurate up to ranges of 4500m to 5700m depending on the The fuze contains a delayed arming feature that ensures the fuze remains unarmed and detonator safe for a minimum of 1.25 seconds of flight. Tabulated data. As soon as the sight data are announced, the gunner places it on the sight, lays the mortar for elevation, and traverses onto the aiming post by turning the traversing handwheel and adjusting nut in the same direction. If the mortar section is to operate quickly and effectively in accomplishing its mission, mortar squad members must be proficient in individually assigned duties. The traversing screw assembly is fitted to the clamp assembly, which is pivoted in the center on an arm attached to the elevating leg. It weighs about 9.05 pounds. TM - Technical Manuals (Range 9) TM - Technical Manuals (Range 10) TM - Technical Manuals (Range 11-4) TM - Technical Manuals (Range 11-5) . An ammunition lot number is assigned to each ammunition lot, which is marked on each cartridge and packing container. The company level vehicles also carry a vehicle-mounted 120mm mortar, which is augmented by the 60mm M224 mortar for dismounted use. The increments are individually wrapped with waterproof bags that are not removed. The firing pin must be replaced and the bore swabbed. The American M1 81mm Mortar, like the upcoming M2 60mm Mortar, was based on a French design by Edgar William Brandt (1880-1960). REFER DEFLECTION TWO EIGHT SEVEN FIVE (2875), REALIGN AIMING POSTS. To dismount the mortar, the squad leader commands, OUT OF ACTION. It uses the M205 propelling charge, consisting of four horseshoe-shaped increments fitted around the tail. The vertical cross line of the sight is on the left edge of the aiming point. The gunner is given a deflection change between 5 and 25 mils, either increasing or decreasing from the last stated deflection, and the command to refer and realign aiming posts. It is used for records such as reports on condition, malfunctions, and accidents. a. Despite its weight though, the 81mm mortar was an important part of the Table of Organization and Equipment of U.S. Army and U.S. Marine Corps maneuver battalions throughout World War II. Additional information is included on an ammunition data card inside each container. This is accomplished by depressing the barrel until the top of the mask is clear. The cartridge is painted olive drab with yellow markings. d. The ammunition is protected from mud, sand, dirt, and water. M3A1 Baseplate These cartridges are used first in subsequent firing so that once-opened stocks can be kept to a minimum. The mortar should be within two turns of center of traverse when the task is compete. The fuze has a safety wire that must be removed before firing. The cartridge is dropped down the barrel, fin-end first. The 0-second boss is wider and differs in shape from the other body bosses; the safe setting position is indicated by the letter "S" on the fuze body. 107 Army Pentagon The bipod provides front support for the barrel and carries the gears necessary to lay the mortar. (d) Firing is slowed if mask clearance must be checked before each firing but this can be eliminated if minimum mask clearance is determined. Close approach to crests, trees, towers, large buildings, parked aircraft, mechanized equipment, and similar irregularities causes functioning at heights greater than average level. b. High angles of approach (near vertical) give the lowest burst heights. If the barrel is hot, the gunner may then apply water to the outside of the barrel until it is cool. Ammunition Lot Number. He releases the securing strap, loosens the leg-locking handwheel, and lowers the plain leg until the locating catch engages in the recess. The barrel clamp, which consists of an upper and lower clamp, is situated at the top. An M18 fuze wrench is used to change settings. Figure 4-7. The fuze arms and functions normally when fired at any angle of elevation between 0800 and 1406 mils at charges 1 through 9. The equipment is placed out the same as for the gunner's examination (Chapter 9). The ignition cartridge has a percussion primer and is assembled to the end of the fin assembly. An air cavity can form on one side of a cartridge to unbalance it, causing instability in flight. Washington DC 20310-0107, ADRP - Army Doctrine References Publications, ATTP - Army Tactics, Techniques, and Procedures, FY Publication Status Report (CAC required for access), Publishing Resources (CAC required for access), PC/PCO/FMO/EPCO Directory (CAC required for access), usarmy.pentagon.hqda-apd.mbx.customer-service@army.mil, GUN, MACHINE, CAL. The squad leader indicates the direction of fire when mounting. High explosive is used for both fragmentation and blast effect against personnel and light-skinned vehicles. The first ammunition bearer puts both hands on the cooling fins under the barrel and slowly lifts the barrel until it is horizontal. With the mortar mounted and the sight installed, the gunner lays the sight on the two aiming posts (placed out 50 and 100 meters from the mortar) on a referred deflection of 2800 mils and an elevation of 1100 mils. 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. Notches in the setter engage ribs in the setting ring of the fuze. Prev - Mk6 Mortar range table for charge 0 Next - Mk6 Mortar range table for charge 2 . When set at SQ, the fuze functions on point impact or graze contact. (1) The rotating socket is free to move in a complete circle. If the situation allows for a longer waiting period, the dud can be considered safe for handling after 40 hours. To make the shift, the gunner places the fingers of his right hand in the muzzle and his left hand on the left leg. Section I. Fired . They use the M5 propelling charge that consists of eight cloth bags attached to the tail unit. To set for delay, the selector slot should be rotated clockwise until it is aligned with the "D" mark on the ogive. When a misfire occurs, any member of the squad immediately announces, "Misfire." FT 81-AI-3 Firing Tables Mortar, 81mm: M28A1 and M29 Mortar 81mm Self propelled M125A1 and M125 Carrier, 81mm Mortar Tracked XM755 [US Army.] The removable increments are fitted onto or around the shaft, depending on their type. After the mortar is mounted, the gunner makes a thorough check. If the primer of the ignition cartridge is dented, the first ammunition bearer attempts to replace the safety wire and places the round in a marked, safe location for disposal by ordnance personnel. d. The M374A2, M374A1, and M374 HE cartridges are painted olive drab with yellow markings and are constructed from pearlitic malleable cast iron. The assistant gunner carries the bipod to the front of the barrel and places the bipod feet on the ground 12 to 15 inches in front of the baseplate and astride the line of fire. [1] [2] Many countries use or used an 81 mm mortar in their armed forces. The Mark 4 and 5 barrels were introduced during World War 2 and have a much increased range. b. SQUAD AND SECTION ORGANIZATION AND DUTIES, Each member of the infantry mortar squad has principle duties and responsibilities. The body is made of aluminum and brass. Each squad member should be able to perform all the following premount checks: a. The cartridge is painted light green with black markings and one narrow brown band. 60mm, 81mm, and 120mmMortar Increments. 60MM M224A1. He positions the lower barrel clamp against the lower stop band on the barrel and secures the upper barrel clamp. The propelling charges are assembled around the fin assembly shaft. The assistant gunner attempts to maintain the traversing mechanism on a horizontal plane. He exposes 1 inch (25 millimeters) of cross-level shaft and folds the handle. (4) Extra increments are removed if the cartridge is to be fired with less than full charge. b. a. If the round does not fire, the gunner tests the barrel for heat. This round must be stored in a vertical position. (2) The ribs and braces have no breaks, cracks, or dents. The term "danger close" is included in the call for fire when there are friendly troops or positions within a prescribed distance of the target, specifically 600 meters for artillery or mortars . It has four function settings: PRX (proximity) causes the cartridge to explode between 3 and 13 feet above the ground; NSB (near-surface burst) causes the cartridge to explode up to 3 feet above the ground; IM (impact) causes the cartridge to explode on contact; and DLY (delay) incorporates a 0.05-second delay in the fuze train before exploding the cartridge. (a) Since the mortar is normally mounted in defilade, there could be a mask such as a hill, tree, building, or rise in the ground. For those of you in the market for a Dummy/Display 81mm mortar, I hope this article can answer a few of your questions before you order. (2) The M84 fuze is a single-purpose, powder-train, mechanical-time fuze used with the 81-mm M301A1 and M301A2 illuminating cartridges. It has no safety pins or wires to reduce preparation time. The cartridge is painted olive drab with yellow markings and weighs about 9.05 pounds. This action breaks an internal sheet pin and internal wire, thereby disabling the proximity function. 4-12. The components of the mortar consist of a cannon, mount, and baseplate. Mount (2) Color code. The following are authorized (Standard B) cartridges for the 81-mm mortar, M252: Each cartridge has fins around the tail to stabilize it in flight and to cause it to strike fuze-end first. Other armies count on 81mm mortar families. The components of the mortar consist of a cannon, mount, and baseplate. They should not be approached for 5 minutes or disturbed for at least 30 minutes after firing. He must ensure that the ball-shaped end of the locking rod is secured in its recess by the locking latch. While the assistant gunner supports the barrel, the gunner slackens the leg-locking handwheel, releases the locating catch, and positions the plain leg. The M821/M889 are 81mm HE Mortar Cartridges. 81 mm HE mortar projectiles generally contain anywhere between 400 g and 680 g of HE and have a maximum range of approximately 6,500 m. 82 mm HE mortar projectiles generally contain anywhere between 392 g and 680 g of HE and have maximum ranges of between 3,000 - 5,500 m. Types of rounds, classification, and characteristics for the 81-mm mortar, M252. The standard infantry support weapon is the M-252 81mm mortar, which lobs a 10 lb. The M1 became the standard American . After the 30-minute waiting period, the dud is still dangerous but can be approached and removed carefully or destroyed in place by qualified disposal personnel. The gunner stands to the left side of the mortar where he can manipulate the sight, elevating handwheel, and traversing handwheel. f. Installation. He makes large deflection shifts by shifting the bipod assembly and keeps the bubbles level during firing. The gunner can depress the barrel, if necessary, to provide easier access to the firing pin. The following safety checks must be enforced before firing the mortar. a. b. Red phosphorus rounds can be fired from the M29/M29A1 at a reduced charge (maximum charge = charge 2). It contains white phosphorus that produces white smoke on contact with air. The M375 cartridge uses the M90 propelling charge while the M375A2 and M375A1 cartridges use the M90A1 propelling charge. When targets are beyond such irregularities, a clearance of at least 30 meters should be allowed to ensure maximum effect over the target area. The M821 HE cartridge (M252 only) is a British-made cartridge fitted with the US M734 multioption fuze. Safety before firing is provided by a safety wire, which must be removed just before firing. The fuze is nicely marked and is dated 1940. If water is not available, the gunner must stand clear of the mortar until the barrel is cool. To prepare for firing, the slot is aligned in the striker with SQ or delay using the M18 fuze wrench. a. d. The gunner removes the sight from its case, mounts it on the mortar, and sets a deflection of 3200 mils and an elevation of 1100 mils. A lock ( c. After the gunner has announced, "Up," the squad leader should check the mortar to determine if the exercise was performed correctly. The superior flow characteristics of these BALL POWDER . a. Correct way to open an ammunition box. The M751 is fitted with a smoke charge that operates on impact. Before the mortar is mounted, the squad must perform premount checks. An official website of the United States government. .50: BROWNING, M2 (HEAVY BARREL, TURRET TYPE) ON MOUNT, MACHINE GUN, TRAILER MTD: MULTIPLE CAL. The tabulated data of the 81-mm mortar, M252, are shown in Table 4-1. Weights (pounds) System (including basic issue items) Barrel (with blast attenuator device) Mount M3A1 Baseplate The muzzle end has a short tapered lead-in which acts as a . (4) The blast attentuator device is secured correctly. Both the 60mm and 120mm mortar rounds use White Phosphorus. Check the post SOP before applying the following procedure: (1) Select a place at least 100 meters from the mortar position, parked vehicles, and ammunition piles. 4-4. Attached to the right of the screw is the traversing handwheel. The barrel clamps are then closed. 81mm smoothbore mortar Barrel length 1.28 m Muzzle velocity 225 m/s Elevation +45 to +85 Traverse 18 Fire control Sights C2 indirect fire sight with illumination Firepower Rate of fire 20 rpm maximum 15 rpm normal 1 to 12 rpm sustained Range 5.650 m maximum 100 m minimum Media 81mm L16A2 DESCRIPTION. He has the duty of preparing the ammunition and passing it to the assistant gunner. That is generally how I use mortars. Both the M90 and M90A1 propellants are in nine wax-tested, cotton cloth, bag increments assembled to the tail unit.

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