WP cartridges are stored with the fuze end up. They are painted light green with red markings and one narrow yellow band. It arms within a maximum of 2.50 seconds. The squad leader picks up the sight case and the two aiming posts, and moves to the exact position where the mortar is to be mounted. The mount consists of elevating and traversing mechanisms and a bipod (Figure 4-4). When set at delay, the fuze train causes a 0.05-second delay before functioning. b. Fired . Long Range PGK. (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. 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. CANNON, 155MM HOWITZER, M185 ON HOWITZER, MEDIUM, SELF-PROPELLED, 155MM, M109A1 HOWITZER, MEDIUM, SELF-PROPELLED, 155MM, M109A1B HOWITZER, MEDIUM, SELF-PROPELLED, 155MM, M109A2 HOWITZER, MEDIUM, SELF-PROPELLED, 155MM, M109A3 HOWITZER, MEDIUM, SELF-PROPELLED, 155MM, M109A3B HOWITZER, MEDIUM, SELF-PROPELLED, 155MM, M109A4 AND CANNON, 155MM HOWITZER, M284 ON HOWITZER, MEDIUM, SELF-PROPELLED, 155MM, M109A5, M109A6 AND M109A7 AND CANNON, 155MM HOWITZER, M284A2 CHROME ON HOWITZER, MEDIUM, SELF-PROPELLED, 155MM, M109A6 AND M109A7 AND CANNON, 155MM HOWITZER, M199 ON HOWITZER, MEDIUM, TOWED, 155MM, M198 AND CANNON, 155MM HOWITZER, M776 ON HOWITZER, MEDIUM, TOWED, 155MM, M777, M777A1 AND M777A2 AND CANNON, 155MM HOWITZER, M776 CHROME ON HOWITZER, MEDIUM, TOWED, 155MM, M777A2 FIRING PROJECTILE, HE, M795 PROJECTILE, HE, M795 IM PROJECTILE, HE, M1122 PROJECTILE, IR ILLUMINATING, M1123 PROJECTILE, ILLUMINATING, M1124 INCLUDES FIRING TABLES FOR PROPELLANTS: M119A2 (CHARGE 7R), M203A1 (CHARGE 8S), AND MODULAR ARTILLERY CHARGE SYSTEM (MACS) PROPELLANTS: M231 (CHARGES 1L AND 2L), M232 AND M232A1 (CHARGES 3H, 4H AND 5H) (S&I BY PROP SEE DETAILS, FOOTNOTES) . The M751 is fitted with a smoke charge that operates on impact. He must ensure that the ball-shaped end of the locking rod is secured in its recess by the locking latch. Burst Height. After the rounds have been removed, they should always be handled with two hands to prevent accidental dropping. Correctly applying and performing these duties enables the mortar section to perform as an effective fighting team. The M751 fuze is the only dummy fuze used with the 81-mm mortar. The M252 81mm Medium Extended Range Mortar is a crew-served, medium weight mortar which is highly accurate and provides for a greater range (4,500 meters to 5,650 meters) and lethality than the . Illuminating is used for battlefield illumination and signaling. It is designed to be fired in the indirect fire mode, cannot be fired handheld, and norm ally utilizes a FDC. This ensures that the mortar does not fire should the round slip down the barrel during the subsequent drills. The ignition cartridge (with primer) is fitted into the base of the fin shaft. M252A1 81mm Mortar: Maximum Range (meters): 5,935; Ammunition: War reserve HE (M821A3), red phosphorus smoke (M819), visible light illumination (M853A1), infrared illumination (M816), war reserve and training HE (M889A4), and FRP . The leg-locking handwheel must then be tightened by hand, ensuring the teeth on either side are correctly meshed. The floating firing pin located within the primer has approximately 1/16 of an inch to move around. If the line of sight clears the mask, it is safe to fire. The adjustment ring has six raised ribs for use in conjunction with fuze setter, M25, and a setting indicator rib (marked SET) about half the height and width of the other six ribs. Agreed that mortars should generally be used close to the frontline. Joint Tables of Allowance; PB - Professional Bulletins; STP - Soldier Training Publications; TC - Training Circulars; . If the barrel is cool enough to handle, the crew removes the round as described below. a. .50: BROWNING, M2 (HEAVY BARREL, FLEXIBLE) ON MOUNT, MACHINE GUN, TRIPOD MTD, CAL. At extreme temperatures (below -40 degrees Fahrenheit and above 125 degrees Fahrenheit), it is not unusual to experience an increase in malfunctions proportionate to the severity of conditions. The sight is laid on 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 wrench (P/N 9349539) sets M772 MT and M768 time fuzes. 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. Remaining increments are repositioned towards the rear of the tail fin assembly when firing the cartridge with horseshoe-shaped increments at less than full charge. c. Mechanical Time. If the situation allows for a longer waiting period, the dud can be considered safe for handling after 40 hours. The gunner is given a deflection change in a fire command between 20 and 60 mils inclusive. The M29 would become the standard American mortar in the upcoming Vietnam War. 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. d. The first ammunition bearer stands to the right rear of the mortar. The gunner places the outer edge of the baseplate against the baseplate stake so that the left edge of the cutaway portion of the baseplate is aligned with the right edge of the stake (Figure 4-7). The baseplate (Figure 4-5) is of one-piece construction, and supports and aligns the mortar for firing. A spring-loaded locating catch is behind the elevating gear housing, which locates the plain leg in its supporting position for level ground. A plain leg is fitted to a stud on the elevating leg and is secured by a leg-locking handwheel. (4) The leg-locking handwheel is hand tight. A locked padlock When the approximate alignment is completed, the gunner signals the assistant gunner to lower the bipod by pushing down on the mortar. During firing, the breech plug on the barrel is sealed and locked to the rotatable socket in the baseplate. Prev - Mk6 Mortar range table for charge 0 Next - Mk6 Mortar range table for charge 2 . The cartridge is painted olive drab with yellow markings. All elements given in the fire command are repeated by the squad. d. The gunner recovers the baseplate to the area designated by the squad leader. 81MM M252A1. REFER DEFLECTION TWO EIGHT SEVEN FIVE (2875), REALIGN AIMING POSTS. Do not burn increments in piles but spread them in a train 1 to 2 inches deep, 4 to 6 inches wide, and as long as necessary. (7) When opening an ammunition box, the ammunition bearer ensures the box is horizontal to the ground, not nose- or fin-end up. Proximity-fuzed short cartridges, which are duds, contain a complete explosive train and impact element. They function normally in light rain; however, heavy rain, sleet, or snow can cause an increase in the number of early bursts. Mount, M177, in folded position. Following the arm-and-hand signals of the gunner (who is looking through the sight unit), he moves the far aiming post so that the gunner obtains an aligned sight picture. (3) The circlip is correctly located, securing the rotating socket to the baseplate. Finally, the assistant gunner loosens the leg-locking handwheel, presses the spring-loaded locating catch, and raises the plain leg behind the buffer cylinders until it touches the traversing handwheel. Designed by Thingsym. The cartridges are painted olive drab with yellow markings. They use the M5 propelling charge that consists of eight cloth bags attached to the tail unit. The cartridge uses the M218 propelling charge, which consists of four horseshoe-shaped increments fitted around the tail. The cartridge is painted light green and has red markings and one narrow yellow band. e. Dummy. Both the M90 and M90A1 propellants are in nine wax-tested, cotton cloth, bag increments assembled to the tail unit. Theme by TechDoc. Mount The M252 is highly accurate up to ranges of 4500m to 5700m depending on the The first ammunition bearer shakes the barrel to dislodge any remnants from the last round fired, and he lowers the barrel into the rotating socket of the baseplate. He rotates the socket so that the open end is pointing in the direction of fire. The sight bracket is attached to the buffer carrier, which is fitted to the traversing screw assembly. c. The gunner grasps both ends of the traverse screw assembly and supports the mortar during the subsequent drill. . The gunner levels the elevation bubble by turning the elevation micrometer knob and reading the setting on the elevation scale and elevation micrometer--this setting is the minimum mask clearance. d. The gunner rough levels the cross-level bubble by making the bubble bounce from one side to the other. Fort Belvoir, VA 22060 If the primer is not dented, the round may be used again. Additionally, they carry the 81mm M252 mortar that can only be used in a dismounted capacity. The M301A3 cartridge has a cylindrical body that contains an illuminating candle and parachute assembly. VERY NICE condition! b. Fuzes are not disassembled. The fuze is not intended to function at charge 0. The cartridges are returned to their original containers. He has the duty of preparing the ammunition and passing it to the assistant gunner. He knocks down the near aiming post and proceeds to the far aiming post. . General Dynamics Ordnance and Tactical Systems is the leading manufacturer of propellants for 60mm, 81mm and 120mm Mortar Systems. b. Range Minimum to maximum 83 to 5,608 meters Rate of Fire . It uses the M185 propelling charge that consists of eight increments fitted into the spaces between the fins and held by a propellant holder. (2) The ribs and braces have no breaks, cracks, or dents. The increments are individually wrapped with waterproof bags that are not removed. MFCS Dismounted. Cartridges assembled with the M524 (A1, A2, A3, or A4) fuze are for use by the US Marine Corps and US Navy only. All rounds are colored according to their type. This is the inert PD fuze type "IR-81" used by the Italians for their 81mm mortar rounds during WWII. Each squad member should be able to perform all the following premount checks: a. Both the 60mm and 120mm mortar rounds use White Phosphorus. However, since explosives are affected by moisture and high temperature, they must be protected. Upon completion of any bipod movement on the barrel, the gunner ensures that the firing pin recess is facing upward. The fuze wrench, M18, assembles the fuze to the cartridge, and the bladed tip on the end sets PD-type fuzes. The gunner is given an administrative command to lay the mortar on a deflection of 2860 or 2740 mils. The aluminum tail assembly has six integral fins equally spaced around the rear, which stabilize the round in flight. The barrel clamp, which consists of an upper and lower clamp, is situated at the top. SQUAD AND SECTION ORGANIZATION AND DUTIES, Each member of the infantry mortar squad has principle duties and responsibilities. The tabulated data of the 81-mm mortar, M252, are shown in Table 4-1. The M853 and M301A3 illuminating ammunition are described herein. More uniform firing is obtained if ammunition is kept at the same temperature. He places the sight case and aiming posts to the left front of the mortar position. He opens the cross-level handwheel, traversing handwheel, and barrel clamp. Each cartridge weighs about 10 pounds and is provided with the M223 propelling charge, consisting of four horseshoe-shaped increments fitted around the tail. (3) From this train, extend a starting train that will burn against the wind of single increments laid end to end. The fuze body is graduated from 0 to 25 seconds in 1-second intervals; 5-second intervals are indicated by bosses. MFCS Mounted. 81-mm MORTAR, M252 The 81-mm mortar, M252, delivers timely, accurate fires to meet the . (See FM 7-90 for a discussion of the duties of the platoon headquarters.). a. The M1 was a derivative of the French mle 27/31 system (itself an improved form of the Stokes Trench Mortar of World War 1 fame) and slightly altered to suit American needs. .50 MACHINE GUN, M3; FIRING CARTRIDGE, CAL. REFERRING OF THE SIGHT AND REALIGNMENT OF AIMING POSTS USING M64 SIGHT. The elevation change announced must be less than 90 mils and more than 35 mils. (d) Firing is slowed if mask clearance must be checked before each firing but this can be eliminated if minimum mask clearance is determined. The fuze setter, M25, sets M84-series time fuzes. The M375A3 cartridge is ballistically similar to the M374A3 (HE) cartridge. LARGE DEFLECTION AND ELEVATION CHANGES. The M252 81mm medium extended range mortar (see diagram below) is a crew-served, smooth bore, muzzle loaded, high angle of fire weapon system. If required, the gunner/assistant gunner lowers the barrel so that the breech plug engages with the open end of the socket, and he uses the barrel as a lever to move the socket. If the round fires, the mortar is re-laid on the aiming point and firing is continued.
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