M252 81mm Mortar

INTRODUCTION: Good morning, my name is your name and my period of instruction is on the M252 81mm Mortar. We will cover some basic mortar knowledge including nomenclatures, rates of fire, and weight. We will also cover the mission of an 81mm mortar platoon and how that platoon is configured. The purpose of this period of instruction is to provide you with basic information and working knowledge of the 81mm mortar.

LEARNING OBJECTIVES:

     a. TERMINAL LEARNING OBJECTIVE: To familiarize you with the main                components and characteristics of the 81mm mortar.

     b. ENABLING LEARNING OBJECTIVES:
          a. State the three main components of the mortar and their nomenclature.
          b. State the weights of the three main components of the mortar.
          c. State the maximum range of an 81mm mortar.

METHOD / MEDIA: I will use the lecture method and the mortar you see in front of you. There will be no posttest after this period of instruction. Are there any questions about your learning objectives or the method and media?

TRANSITION: Now if there are no questions for me let’s get into the nuts and bolts of this period of instruction.

BODY:

     MISSION:      The 81mm mortar platoon is commonly called the battalion           commander’s hip pocket artillery. It is called this because 81’s are foot                mobile, are on target faster, and more accurate than artillery. The                     mission of the 81mm mortar platoon is to provide continuous indirect                fire support to the infantry battalion and it’s subordinate elements in the                offense and defense.      
     
CHARACTERISTICS: The M252 81mm mortar is a smooth bore, muzzle loaded, high angle of fire weapon. Smooth bore meaning it has no lands and grooves like a rifle barrel. Muzzle loaded, because you insert a round into the muzzle of the cannon, allowing gravity to pull the round down, striking the firing pin. High angle of fire because it is capable of firing from within defilade, over hills, and other obstructions.

COMPONENTS: The M252 81mm mortar consists of three main components, and a dovetail slot sight. They are:

M253 Cannon (barrel): The M253 cannon consists of the barrel, sealed at the lower end with a removable breech plug that houses a removable firing pin. At the muzzle end is a cone-shaped Blast Attenuator Device (BAD) that is fitted to reduce noise.
          
M177 Mount (bipod): The M177 mount is composed of 3 main assemblies. They are: the leg assembly, the traversing gear assembly, and the barrel clamp assembly.

          M3A1 Baseplate: The M3A1 baseplate is of one-piece construction. It                supports and aligns the mortar for firing. During firing, the breech plug                on the barrel is sealed and locked to the rotate able socket in the                     baseplate.

          M64A1 Dovetail Slot Sight: The M64A1 sight is provided for laying the                mortar. The cross level vial is used to ensure that the sight and mortar                are kept upright. By using the telescope, deflection scales, and                     cross level vial, the mortar is laid for direction. By using the elevation                scales, elevation vial, and cross level vial, the mortar is laid for elevation.                The sight is illuminated by tritium gas. After the sight has been set for                deflection and elevation, the mortar is elevated or depressed until the                elevation bubble is level. The mortar is then traversed until a proper                sight picture is seen (using the aiming posts), and the cross level bubble                is level. The mortar is laid for deflection and elevation when all bubbles                are level, and a correct sight picture is obtained.

          Major Parts: The sight unit has two major parts. They are the elbow                telescope and the telescope mount. The elbow telescope is a fixed                     power 1.5 power sight. It consists of a clamping mechanism,                     rubberized eye shield and the telescope itself. The elbow telescope is                considered the sight unit’s upper section. The telescope mount consists                of a course deflection scale, and fine deflection scale, a course elevation                scale, and a fine elevation scale.

     PHYSICAL CHARACTERISTICS:

          WEIGHT:
               
               Barrel (w/BAD)               35lbs.
               Bipod                         27 lbs.
               Baseplate                    29 lbs.

          ELEVATION:

               Elevation                    0600 - 1600 mils
               Per each turn of elevation          10 mils
               Total cranks on elevation crank     50.5 turns

          DEFLECTION:

               Right or Left from center traverse     100 mils
               Total deflection               6400 mils (360 degrees)
               Traversing                    28.5 turns (left to right)
               Minor adjustment               25 turns

          PERFORMANCE:

               Maximum range               5733 meters
               Minimum range               100 meters
               Danger close (training)          400 meters

          RATE OF FIRE:

               Sustained                    15 rounds per minute
               Maximum                    30 rounds per minute

PERSONNEL: The personnel of a mortar platoon are tactically deployed in one of three places:

               1. Mortar Position
               2. Fire Direction Center (FDC)
               3. Forward Observer Teams (FO)

QUESTIONS:

     QUESTIONS FROM THE CLASS:
     Q. Where is the dovetail slot located?
     A: On the bipods.

     QUESTIONS TO THE CLASS: If you have no additional questions for me, then I      have some questions for you.

     Q. What is the nomenclature of the cannon?
     A. M253

     Q. What is the maximum range of the 81mm mortar?
     A. 5733 meters.

SUMMARY: Today we have covered the basic components, the characteristics, where personnel are located, and the mission of the 81mm mortar platoon. With this valuable information you now have some basic knowledge of the 81mm mortar and how it works.




References:

     FM 23-90 Mortars
     FM 23-91 Mortar Gunnery
     Marine Corps Institute 03.22 M252 81mm Mortar Crewman
     Marine Corps Institute 03.31 81mm Mortar NCO (Non-Commissioned Officer