Indirect Fire Weapons



Gunnery Department JAN 97

Fort Sill, Oklahoma






TIME ALLOTTED: 4 periods (240 minutes).

CLASS PRESENTED TO: Field Artillery Officer Basic Course (FAOBC).

TOOLS, EQUIPMENT, AND MATERIALS: Auditorium, equipped with M119 howitzer with pantel, collimator, aiming posts with lights, ovation system, pentium computer, short, extremely long and laser pointers, FM 6-50, ST 6-50-19,

Phase I Notebook.

PERSONNEL: One principal instructor.

TRAINING AIDS: Ovation system, M119 howitzer and close-in aiming points.

REFERENCES: FM 6-50, ST 6-50-19.

STUDY ASSIGNMENTS: Read FM 6-50, chapter 1, chapter 2, APPX D, para D-1 through D-4, and Glossary. Read ST 6-50-19, chapter 1 and 2.


Uniform - Appropriate seasonal uniform

Equipment - FM 6-50, ST 6-50-19 and phase I tish book (GCO2FA SO-1).



ADVANCED ARRANGEMENTS: One day prior, up-load slide presentation onto available pentium computer for room 8 SuH. Emplace M119 howitzer in Rm 8 in firing configuration with sights mounted, collimator emplaced (left rear) and aiming posts with working lights. Ensure tish is issued to students prior to class.

CONDUCT OF CLASS: Conduct a conference on the various FA Terms, using demo’s to emphasis and elaborate ideas and definitions.

TIME CONTROL: FA Terms.............................................150 min.

Breaks............................................... 30 min.


REVIEWED BY THE DIVISION CHIEF_____________________________DATE____________

REVIEWED BY THE FABSO______________________________________DATE____________

Section I



The mission of the Field Artillery is to destroy, neutralize, or suppress the enemy by cannon, rocket or missile fire and to help integrate all fire support assets into combined arms operations. In order to accomplish this mission, the Field Artillery must be able to rapidly and accurately exchange information with certain terms, procedures and weapon formations that enhance the artillery’s survivability and flexibility on the modern battlefield.


In order for you to exchange information on a professional level, it is imperative that you learn the proper terminology used by artillerymen throughout the world.


a. Given FM 6-50 and elaborate demonstrations, rapidly and accurately understand professional terms and definitions providing prerequisite knowledge on which the course builds.


a. Understand how howitzer batterys are organized, lead, and emplaced on the modern day battlefield.

b. Understand the terms necessary to orient the howitzer battery for direction.

c. Understand the corrections for displacement with close-in and distant aiming posts.

d. Select the proper meaning for the following terms:

(1) Platoon Based Field Artillery Battalion.

(2) Battery Based Field Artillery Battalion.

(3) Battery Commander.

(4) First Sergeant.

(5) Platoon Leader/Executive Officer.

(6) Fire Direction Officer.

(7) Platoon Sergeant/Chief of Firing Battery.

(8) Gunnery Sergeant.

(9) Chief of Section.

(10) Artillery Carriages.

(11) Recoil Mechanisms.

(12) Barrel Components.

(13) Sliding Wedge Breechblock.

(14) Interrupted Screw Breechblock.

(15) Firing Mechanism.

(16) Auxiliary Devices.

(17) Muzzle Break.

(18) Functioning of the Cannon.

(19) Numbering of Howitzer Sections.

(20) Line Formation.

(21) Lazy "W" Formation.

(22) Diamond Formation.

(23) Terrain Gun Positioning.

(24) Recon, Selection and Occupation of Position (RSOP).

(25) Hot Sections.

(26) Line of Fire.

(27) Rearward Extension of the Line of Fire.

(28) Azimuth of Fire/Azimuth of Lay.

(29) Direct Laying.

(30) Indirect Laying.

(31) Orienting Station.

(32) Orienting Line.

(33) End of Orienting Line.

(34) Orienting Angle.

(35) Precision Lightweight Global Positioning System Receiver (PLGR).

(36) Declination Constant.

(37) Instrument Reading.

(39) M2A2 Aiming Circle.

(40) Gun Laying and Positioning System (GLPS).

(41) Panoramic Telescope (Pantel).

(42) M100 Series Sight.

(43) Boresighting.

(44) Aiming Point.

(45) Close-in Aiming Point.

(46) M1 Infinity collimator.

(47) Aiming Posts.

(48) Far Posts.

(49) Near Posts.

(50) Distant Aiming Point.

(51) Deflection.

(52) Refer.

(53) Gunner’s Reference Card.

(54) Common Deflection.

(55) Deflection Clutch/Counter Reset Knob.

(56) Two-Step Deflection Method.

(57) LARS Rule.

(58) Displacement.

(Knowledge level objectives).


6. SAFETY STATEMENT Safety precautions have been reviewed and are not applicable.



Section II


SLIDE 1 USAFAS CROSS CANNONS. Slide showing prior to students arrival.

SLIDE 2 Title Slide Field Artillery Terms.

SLIDE 3 Mission of the Field Artillery. The mission of the Field Artillery

is to destroy, neutralize or suppress the enemy by cannon, rocket or

missile fire and to help integrate all fire support assests into

combined arms operations.


1. The Field Artillery System. The Field Artillery System links together the different parts of the Field Artillery so that we can provide fire support to the maneuver units. This system is made up of the following components; Target Acquisition, Command and Control, Gunnery, and Weapons and Ammunition. we like to think of Target Acquisition as the eyes of the Field Artillery, the Command and Control and Gunnery as the brains, and Weapons and Ammunition as the muscle of the Field Artillery.


a. Target Acquisition. These assets are anything that gives information concerning the nature and location of a target. The targeting intelligence is sent to the Fire Direction Center. Some of the common Target Acquisition assets are:

(1) FIST and COLT Teams.

(2) Q-36 Radar.

(3) Q-37 Radar.

b. Field Artillery Battalion. There are currently two configurations of Artillery Battalions.


(1) Platoon Based(3 x 6) Battalion consists of a headquarters and headquarters battery, service battery and three firing battery’s of two firing platoons each.

(a) Headquarters and Headquarters Battery is where you will find the command and control elements for the battalion. The Sl, S2 and S3 are located in HHB, as well as battalion survey and communications section.

(b) Service Battery is where you will get the support to

perform your mission. Service Battery provides ammunition, food and

maintenance assets to the battalion.


(c) Platoon Based Firing Battery will consist of two Firing Platoons EACH consisting of 3 or 4 howitzer sections (M109A3/A5 = 3, M198 = 4) 1 FDC and 1 ammo section. A Headquarters platoon that contains a mess section (ususally OPCON to SVC Btry), commo section, supply section, NBC and a headquarters element.



(2) Btry Based (3 x 6) Battalion consists of 3 firing batterys, Headquarters & Headquarters and Service Battery. The major differences are found at the Battery level.


(a) Btry Based Firing Battery will have a Headquarters Platoon similar to the 3 x 8 Firing Battery with the addition of an ammo section.

(b) The balance of the Battery consists of 6 howitzers and 1 FDC.


(3) Number of cannon sections per battery:

(a) 3 x 6 (platoon based Bn) - Three firing batteries of 2 platoons of 3 sections each. 18 howitzers per battalion. These units consist of M109A3/A5s.

(b) 3 x 6 (Btry based Bn) - Three firing batteries of 6 sections

each. 18 howitzers per battalion. These units consist of M119A1s (USA), or M198s (USMC only).

(c) 3 x 8 (platoon based Bn) - Three firing batteries of 2

platoons of 4 sections each. 24 howitzers per battalion. These units consist of M198s.


(4) Platoon based command and control consists of the Btry HQs, Platoon operations center (POC), FDC and Howitzer sections (use slide to add in key leader locations).


(5) Battery based command and control consists of the Btry HQs, Battery operations center (BOC), FDC and Howitzer sections (use slide to add in key leader locations).

(6) The Battery Command and Control will be dependent on the type of battalion; Btry vs. Platoon Based. The command and control element dictates employment and deployment guidance for each unit. At the battery level we have the Battery Commander and the First Sergeant.


(a) The Battery Commander is responsible for everything the battery does or fails to do. He conducts an in-depth recon and selection of proposed battery positions. The BC is also the link between the battery and higher headquarters. In Btry Based operations he will lead the advance party.


(b) The First Sergeant is the BC’s principle enlisted assistant and is the senior enlisted man in the battery. In a Btry Based unit he will organize the perimeter defense and in Platoon Based he will integrate the platoon defense plans into a total battery defense plan. In the USMC the First Sergeant has ONLY administrative duties.



(5) The Platoon Command and Control varies from Battery Based.

(a) The Platoon Leader/Executive Officer is the Tactical Commander of the platoon (3 x 8)/supervisor of the firing battery (3 x 6) during 24 hour operations the PLT LDR/XO must aid the FDO in his duties so the FDO can rest. The USMC has an Assistant XO which assists both the XO and FDO.


(b) The Fire Direction Officer (FDO) supervises and trains the FDC and controls the firing of the platoon/battery. He must know and be prepared to assume the duties of the platoon leader/executive officer.


(c) The Platoon Sergeant/Chief of Firing Battery is the PLT LDR/XO's principal enlisted assistant. He directly supervises the cannon section chiefs and must be prepared to assume any of the platoon leader duties in his absence. He is responsible for platoon perimeter defense in Platoon Based operations. The equivalent USMC billet description is the battery gunnery sergeant (Btry GySgt).


(d) The Gunnery Sergeant will assist the platoon sergeant/chief of firing battery in executing his duties. He must also be prepared to assume any of the platoon leaders/executive officer's duties. He will conduct (in depth) the detailed RSOP of the PLT position in platoon based operations. In Btry based operations he will assist the first sergeant. The equivalent USMC billet description is the local security chief. He must be capable to assume the btry gunnery sergeants responsibilities.


c. Fire Direction Center. The FDC receives data transmitted by target acquisition assets and converts it into data, fire commands, that can be used by the howitzers to engage the target.


d. Chief of Section. This consists of the cannon sections and ammunition sections. The Cannon section refers to the howitzer itself and the men and the equipment used to engage targets. The Chief of Section is the senior enlisted man located on each weapon. He is responsible for supervising all section personnel on the employment and deployment procedures and considerations of the weapon. Each cannon section has either a towed or a self propelled howitzer, an ammo carrier and/or prime mover, and the appropriate auxiliary equipment to maintain/sustain the sections firing capabilities.


(1) Numbering the pieces in the battery:

(a) A particular howitzer sections bumper number is associated with each howitzer number (1 through 8 for 3 x 8 units PLT based and 1 through 6 for 3 x 6 units PLT/Btry based). This association does not change from position to position. If a howitzer becomes disabled or misoriented enroute to a new location, its associated numbers and all other howitzer numbers do not change. A unit should stencil its howitzers and travel as necessary so as a unit occupies a position, its howitzers will be numbered in order from right to left, front to rear as the Btry/PLT faces the azimuth of fire.

(b) Coordination between the platoon leader and the FDO is essential to ensure the howitzers are numbered the same on the ground as they are in the Battery Computer System (BCS). The computer maintains individual weapon information used to determine an individual weapons ballistical solution.


2. Employment. When tactically employed the platoons may be side by side or as much as 1600 meters apart according to their mission. The HQ's and support can form a separate perimeter called the battery trains or it may be attached to one of the firing platoons or it can be divided among the two platoons (Discuss the advantages/disadvantages of the 3 basic options for positioning the battery elements: heavy-heavy, heavy-light, light-light).


a. Weapon Formations. The howitzers in a platoon/battery may be employed in any number of formations.

(1) The line formation will allow for maximum ease in and control but it is very vulnerable to air and counterfire attacks. It presents an especially easy target for strafing and low level bombing.

(2) The lazy "W" formation is good for command and control and provides some passive air defense.

(3) The diamond/star formation will provide the unit with excellent 6400 mil firing capability and perimeter defense. Command and control when using this formation can become a bit more difficult.

SLIDE 24 Illustration of Weapon Formations.


b. Terrain Gun Positioning. This is the primary method used for positioning our howitzers. It is the use of terrain to provide the maximum concealment and protection from the enemy by fitting the howitzers into the rolls, folds, and vegetation of the terrain. All support functions located with the firing element should be positioned to the rear of the howitzers to reduce the amount of activity around the gun line.


c. RSOP. RSOP is the Recon, Selection and Occupation of a Position. This procedure ensures a rapid and orderly movement to and occupation of a new firing position so that you can continue to provide timely and accurate fire support.

SLIDE 27 Movement Brief (briefly discuss the importance of information dissemination).


d. Hot Sections. These are cannon sections designated by the commander to maintain full crews, (at their posts), for instant reaction to fire missions, for a designated period of time. This allows the other sections to perform duties such as PMCS on their equipment, personal hygiene, and anything else to maintain mission capability.


SLIDE 30 Cannon Weapon Systems.

3. Basic Components of Cannon Weapon Systems.


a. Artillery Carriages. The carriage supports the weapon in the firing and traveling positions. A weapon is classified as either self-propelled or towed depending on the carriage.


b. Recoil Mechanisms. These are designed to absorb the energy of recoil gradually, avoiding violent shock or movement of the carriage. Use the M119A1 to discuss the recoil parts. The recoil mechanism performs the following functions:

SLIDE 33 Functions of the Recoil Mechanism

(1) Stops the recoiling parts.

(2) Returns the recoiling parts, to the firing (or the in battery) position.

(3) Prevents shock, to the carriage.

(4) Keeps the tube in battery at all angles of elevation.


c. Parts of the cannon tube (slide builds each component).

(1) Breech recess - receives the breechblock.

(2) Powder chamber - houses the propelling charge.

(3) Centering slope - centers the projectile in the bore

during loading.

(4) Forcing cone - tapered lands that allow the rotating band

of the projectile to be engaged gradually by the rifling.

(5) Main bore - rifled portion of the bore forward of the

centering slope.

(6) Counterbore - relieves stress at the end of the tube and

prevents it from cracking.

(7) Swiss groove - (separate loading only) cutaway portion in

the powder chamber where the powder lies prior to firing.

(8) Gas check seat - (separate loading only) provides the rearward seal (rearward obturation) tapered portion of the tube at the rear end of the powder chamber.

SLIDE 35 Rifling Cross Section

(9) Lands and grooves - the rifling, with a right hand twist.


d. Breech - The 105 mm howitzers have a sliding wedge breechblock and the 155mm M109 series and M198 howitzers have interrupted screw breechblocks. M102, M119A1 have vertical sliding wedges.

SLIDE 37 Vertical Sliding Wedge (OPENED)

SLIDE 38 M198 Interrupted Screw Breechblock

SLIDE 39 Interrupted Screws in Breech Recess

SLIDE 40 M109 Interrupted Screw Breechblock


e. Firing mechanism. This is a device located on and in the breech of a howitzer. It is used to fire the primer.

SLIDE 42 M35 in firing configuration


f. Auxiliary devices (bore evacuator and muzzle break build illustration).


(1) Muzzle brake - This is mounted on the muzzle of most US howitzers and consists of one or more baffles. As the projectile leaves the muzzle the high velocity gases following the projectile strike the baffles of the muzzle brake and are deflected toward the rear and sides. The gases exert a forward force on the baffles thereby reducing the force of the recoil.


(2) Bore evacuator - This device removes propellant gasses from the bore after the weapon has been fired. This prevents contamination of the fighting compartment by forcing the gases to flow outward through the bore. This is only found in weapon systems with a turret.

g. Functioning of the Cannon.

(1) When the cannon is fired the firing mechanism initiates the propelling charge explosive train. The rapidly expanding gases from the burning propellant force the projectile through the cannon tube.

(2) When the projectile has passed the 10 evacuator valves ("Jenny balls") some of the gases flow into the evacuator thereby creating a high pressure in the chamber.

(3) As the projectile passes by 3 orifices (angled toward the muzzle) in the tube the pressure in the bore drops and the higher pressurized gases escape from the evacuator into the bore.

(4) As the projectile leaves the weapon the muzzle brake also functions as the gases following the projectile push against the recoil of the weapon.

(5) The breech is automatically opened and the vacuum formed from the escaping gases sucks air through the breech pushing the gases out the muzzle.


4. Basic Emplacement Terms. Ref. FM 6-50, Glossary.


a. Line of Fire (LOF). The direction of the line established by the tube or any line parallel to that line in the firing position. It is an imaginary line extending through the central axis of the tube when looking through the breech to the muzzle of the weapon.

SLIDE 48 LOF Illustration.


b. Rearward extension of the Line of Fire (RELOF). An imaginary line extending through the central axis of the tube when looking down through the muzzle to the breech of the weapon. It is a line in the exact opposite direction of the line of fire.

SLIDE 50 RELOF Illustration. Elaborate your point with the howitzer and large pointer.


c. Azimuth of Fire (AOF)/Azimuth of Lay (AOL). The direction, expressed in mils, that a firing unit is oriented on when it occupies a position. The field artillery uses grid north as a reference point so all AOFs measured from grid north (There can be only one AOF).

SLIDE 52 AOF illustration.

SLIDE 53 AOF/LOF illustration


d. Laying. This is the process of orienting for direction. There are

two types.


(1) Direct laying - aiming of the weapon by sighting directly

on the target.


(2) Indirect laying - aiming of the weapon by sighting on an aiming point other than the target. From this aiming point the weapon is laid for direction and elevation.


e. Accurate firing unit location.

(1) Direction / Location / Altitude. To engage targets with artillery, we need to know the direction to the target, as well as the location/altitude of the target and the firing unit. Target location will be provided to us by target acquisition. We have a number of ways to determine firing unit location and direction to the target.


(2) Survey - Survey will provide us with our location and a known direction. Define survey as the technique of locating points on the Earth’s surface and determining direction. The establishment of a common grid is performed by the highest survey echelon in the area. This information is left in the plt/btry position on a tag including: grid, altitude, and direction to a sharply defined point.


(a) Orienting Station (OS). An OS is a point of known location on the ground which has directional control. It is the point over which the aiming circle is set up.

SLIDE 60 Permanent OS picture.

SLIDE 61 Semi-permanent OS picture.


(b) Orienting Line (OL). An OL is a line of known direction established by survey. This line serves as the basis for laying the howitzers for direction. The OL extends from the OS to the EOL.


(c) End of Orienting Line (EOL). An EOL is a point on the orienting line marked by a sharply defined permanent or semi-permanent object. If possible, it should be visible at night and at least 30 meters from the OS.

SLIDE 64 EOL Permanent marker picture.

SLIDE 65 Elements of Survey (diagram builds with OS, EOL, OL, GN, ANGLE)


(d) Orienting Angle (OA). The OA is the horizontal clockwise angle from the line of fire to the orienting line.

SLIDE 67 Orienting Angle (diagram builds with OS, EOL, OL, GN, LOF, ANGLE, OA).


(3) Determine Location Without Survey - You must determine your location and establish a known direction. Accurate firing unit location is one of 5 requirements for accurate predicted fire (RAPF) which the majority of OBC revolves around. To determine location we can use the Precision Lightweight GPS Receiver (PLGR) or Map Spot our location. If we know where we are and what direction we are oriented and we have the enemies location we can use indirect fire methods to achieve effects on target.

Instructor Note: In order for the United State Army field artillery to use the PLGR to accurately determine location it requires crypto variables (encryption devices) and a figure of merit one (FOM 1). For cannon positioning accuracies we must meet the STANAG requirements of: horizantal Circular Error Probable (CEP) < 17.5M and altitude Probable Error < 10M. The US Army has accepted the PLGRs location determining capability as "Common Grid" when the PLGR is used in the averaging mode FOM1 for 3 minutes. This achieves CEP of < 10M. However, the PLGR can not determine an accurate direction that meets the STANAG requirements and will never be used to orient for direction. If your lucky, you may determine a grid within 10M of your actual location with a map spot.


(4) Determine Direction Without Survey - This can be performed by using hasty survey techniques which is the preferred method when survey is not available. If hasty survey is not available we can determine direction using the M2A2 aiming circle that has been properly declinated.


(a) Declination Constant DC - The DC is the horizontal clockwise angle from grid north to magnetic north. The declination constant should be determined and recorded for every instrument equipped with a magnetic needle. The DC for any instrument will vary in different localities and the DC of different instruments in the same locality will also vary. This variation is due to slight differences in manufacturing and to the shock from handling of the instruments during normal use. (Slide builds with AC, GN, MN, DC).


(b) Instrument Reading (IR) - The IR is the Horizontal clockwise angle from the line of fire to magnetic north.

SLIDE 72 Instrument Reading (diagram builds with AC, GN, MN, LOF, IR).


f. Orienting devices.

(1) M2A2 Aiming Circle - The aiming circle is an optical instrument capable of measuring horizontal and vertical angles. It is the primary instrument used to orient the howitzers onto the azimuth of fire.

(2) Gun Laying and Positioning System (GLPS) AN/PSN-11 - The GLPS supplements the M2A2 aiming circle and will be the primary instrument to orient howitzers in cannon units not equipped with Paladin. When used with the PLGR it will determine location, establish directional control (with built in gyro) and determine distance from the howitzers to the GLPS using an eye safe laser.

(3) M100 Series sight (New Series Sight) - A pantel is an optical fire control instrument found on the howitzer. It is used for both direct fire and indirect fire. The M-100 series sight measures horizontal clockwise angles from the rearward extension of the line of fire only. It measures a maximum of 6400 mils. It is mounted on the M102, Ml19A1, Ml09 series, M198, howitzers.

SLIDE 74 M2A2 Aiming Circle picture.

SLIDE 75 GLPS picture.

SLIDE 76 M100 Pantel picture.

SLIDE 77 Pantels 6400 mil capability (diagram)



h. Boresighting - This is the process by which the optical axis of the weapon sights are aligned parallel to the axis of the cannon tube (use hunting with a scope, if its not zeroed, no meat).

SLIDE 80 Incorrect Boresight picture.

SLIDE 81 Correct Boresight picture with Types of Boresighting.


i. Aiming point - An aiming point is a sharply defined point on which the sight of a weapon is aligned when the weapon is laid for direction. There are two types.

(1) Close-in aiming points are established by the personnel in the battery and there are two types: M1A1 Infinity collimator and Aiming Posts.

(2) Distant aiming points are sharply defined, easily identifiable points located at least 1500 meters from the howitzer. Examples of DAPs are church steeples, trig markers and water towers.


(a) MlAl Infinity collimator is the primary close-in aiming point. It is a lightweight optical instrument that simulates an aiming point at infinity. The optical image has a zero at it's origin with numbers extending upward to the left and right into infinity. It is graduated every mil and numbered every 5 mils. To have a proper sight picture you should see 3 numbers (ex: 5, 0, 5) or eleven one mil graduations or both. When emplaced it should be set up 4-15 meters from the howitzer pantel. To achieve the correct sight picture you must align the numbered vertical- hairlines of the pantel with the corresponding numbers within the optics of the collimator.

SLIDE 84 Collimator Scale with pantel sight picture (focus on graduations, lableing, and visual interpolation).

SLIDE 85 Proper Emplacement of the Collimator diagram (know for all howitzers).

SLIDE 86 Proper Collimator Sight Picture diagram (focus on graduations alignment and need for 3 numbers or 11 graduations visible).


(b) Aiming Posts are striped rods used in pairs, they are equipped with night lighting devices which allow them to be seen at night. The near post is a 4 foot section and the far post is two 4 foot sections put together. When emplacing the aiming posts the near post is placed at one half the distance that the far post is from the pantel. Ideally the far post should be placed 100 meters from the Howitzer pantel. Place the near post in the ground 50 meters from the howitzer in as vertical a position as possible. Walk another 50 meters, turn and hold the Far post vertically in front of you and, taking directions from the gunner, align the far post until it is on line with the Near-post and pantel line. Stick the post in the ground and align it with the gig line of your uniform. Once aligned, move to the near post, hand and arm signals once again will be used to align the near post onto the left edge of the vertical hairline of the pantel. Once emplaced the proper sight picture shows the posts looking as though there is only one post with the Hairline of the pantel aligned on the left edge.

SLIDE 88 Proper Emplacement of Aiming Posts.

SLIDE 89 Proper Emplacement of Aiming Posts (with sight picture).


(3) Distant aiming points are sharply defined, easily identifiable points located at least 1500 meters from the howitzer. Examples of DAPs are church steeples, trig markers and water towers.


(4) Close-in aiming points are movable and established by battery personnel and are visible at night while distant aiming points are stationary objects and may not be visible at all times. The DAP does have the advantage of being readily available upon occupation of a firing position.


5. Deflection. A deflection is the horizontal clockwise angle measured from the line of fire or rearward extension of the line of fire to the line of sight of a designated aiming point with the vertex of the angle at the sight (pantel).

SLIDE 93 Deflection diagram (elaborate on the LOF parallel to tube).


a. Refer. To refer is to measure a deflection to a given aiming point, using the weapon pantel, without moving the cannon tube. These referred deflections are then recorded on the gunners reference card.

SLIDE 95 Refered Deflection diagram.

SLIDE 96 Gunner’s Reference Card picture.


b. Common Deflection. The common deflection is the deflection corresponding to the initial azimuth of fire. In simple terms it converts the azimuth of fire to a deflection. The common deflection for all weapons with the M100 series sight is 3200.

Instructor note: The common deflection for the M101A1 is 2800 and for the M114 series howitzer is 2400, allies may have these systems with M12 series sights.

SLIDE 98 Common Deflection picture.

SLIDE 99 Howitzers Emplacing diagram (hands on pantel to elaborate).

SLIDE 100 Deflection Clutch picture.


(1) Deflection Clutch (released & engaged). The deflection clutch is found on all current towed howitzers. It is used to refer deflections and to establish a common deflection for all the howitzers in the firing position (See TM-10 for procedures).

(2) Counter Reset Knob - The counter reset knob is found on self propelled howitzers M100 series sights and is used to set the sight on 3200 when the howitzer is laid on the azimuth of fire. A good analogy is the trip odometer on a car when pressed returns to 0000. The M100s counter reset knob returns the ‘lower’ azimuth scale to 3200.

SLIDE 102 Howitzers with Common Deflection Established diagram.

Note to instructor: At this time show how the Howitzers orient themselves for direction and then convert the azimuth of fire to the common deflection.


c. Two-Step Deflection Method - This method is used when the gunner must orient the howitzer tube on a deflection.

(1) Step 1: Set off the announced deflection on the pantel.

(2) Step 2: Traverse the weapon until the line of sight is back on the aiming point. The howitzer tube will be traversed either left or right based on the LARS rule.



d. Displacement. Displacement is the angular deviation caused by the movement of the pantel due to the shock of firing or traversing of the tube.


(1) When the Howitzer is traversed, the pantel changes its position because it is not positioned over the pivot point of the rotation it started from.



(2) When the Howitzer is fired, the shock from firing will cause the howitzer to shift backwards.


(3) We will correct for displacement by changing the sight picture with a close-in aiming point.


(a) When using a DAP no correction is necessary because the angular deviation is very minimal due to the distance involved. This can be explained using the mil relation formula. The maximum amount of displacement that can be obtained on any howitzer is 1.5M. X is the range to the DAP (in thousands)

W = m 1.5 = 1 mil 1.5 = X

R X 1

X = 1.5 x 1,000M or 1,500M.

The minimum distance for a DAP is 1,500M. The most displacement can be no more than 1 mil.


(b) When using a collimator the rule to correct for displacement is to match the numbers. Using the slides, show the students the two examples.

SLIDE 111 Corrected Collimator Sight picture.

SLIDE 112 Collimator Displacement to the Right picture.

SLIDE 113 Corrected Collimator Sight picture.

SLIDE 114 Incorrect Aiming Posts Sight picture.




(c) When using aiming posts the rule to correct for displacement is the NFL rule. The NFL stands for Near, Far, Line and the object is to align the near post, the far post and the pantel line equal distances apart. Show two examples using the NFL rule.

SLIDE 116 Corrected Aiming Post Sight picture.

SLIDE 117 Second example of Corrected Aiming Post Sight picture.





Section III



a. The Field Artillery System.

(1) Target Acquisition.

(2) Command and Control.

(3) Fire Direction Center.

(4) Weapons and Ammunition.

b. Employment.

(1) Formations.

(2) Terrain Gun Positioning.

(3) RSOP.

c. Basic Components of Cannon Weapon Systems.

d. Basic Emplacement Terms.

e. Deflection and how to correct for Displacement.

(1) DAP.

(2) Collimator.

(3) Aiming Posts.


Explain that they are now armed with the knowledge that will assist them in the remaining cannon classes in FAOBC but more importantly in assisting them throughout their artillery careers.

Section IV


Section V



This TLO tested formally during the GCO201 exam.

Rapidly and accurately exchange information of certain artillery terms, procedures and weapon formations, without error.

This TLO tested formally during the GC020l exam.