MCWP 3-16.3 FM 6-50 TTP for the Field Artillery Cannon Gunnery - page 9

 

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MCWP 3-16.3 FM 6-50 TTP for the Field Artillery Cannon Gunnery - page 9

 

 

FM 6-50, MCWP 3-1.6.23

7-19. END OF MISSION

The 

command END OF MISSION (EOM) means that the

fire mission has been terminated. The howitzer sections

should return to the azimuth of lay or priority target data.

The SCA displays EOM for that howitzer; for example, GUN

(number so-and-so) EOM.

7-20. PLANNED TARGETS

a. 

The battery may be assigned planned targets for which

current firing data must be maintained. Each target is

assigned a number and each weapon is laid on its assigned

priority target. In such cases, unit SOP usually designates

a command or a prearranged signal to fire on the priority

target, bypassing the usual sequence of fire commands.

EXAMPLE

Target AC7343 has been designated as a priority target.

Firing data have been computed and have been transmitted

to one of the firing platoons. On the command

RIGHT, SUPPRESS AC7343, 

the right platoon engages

Target AC7343 with the previously arranged method of
fire.

b. 

In defensive operations, the command FIRE THE FPF

causes the firing battery to fire the final protective fires on

which it is laid.

7-21. REPETITION AND CORRECTION

OF FIRE COMMANDS

a. 

One section (normally the adjusting piece) of the firing

unit should be designated to read back all voice fire commands

to ensure that the howitzer sections have received the fire

commands correctly. When a command has not been heard

or has been misunderstood, the request for repetition is stated

as a question; for example, DEFLECTION NUMBER 2?

When the FDC replies, the repetition of a command is always

preceded by NUMBER (so-and-so), THE COMMAND

WAS; 

for example, NUMBER 2, THE COMMAND WAS

DEFLECTION 2768.
b. 

If an incorrect command has been given, but the

command QUADRANT  has not been announced, the FDC

commands CORRECTION followed by the correct

command and all subsequent elements. If QUADRANT

has been announced, the FDC commands  CHECK FIRING,

CANCEL CHECK FIRING 

is announced followed by the

corrected element and all subsequent elements.

7-22. FIRING REPORTS

The 

section chief reports to the FDC all actions that affect

the firing of his weapon in support of the battery mission.

During firing, the following specific reports are made:

a. 

When the special instruction DO NOT LOAD has been

commanded by the FDC the section chief reports LAID,

NUMBER (so-and-so).

This report is sent when the

projectile, charge, and fuze (if applicable) have been prepared;

the howitzer has been laid for deflection; and the quadrant

(or loading elevation) has been set.
b. 

When the special instruction AT MY COMMAND or

BY PIECE 

(or BY ROUND) AT MY COMMAND has

been commanded by the FDC, the section chief reports by

voice READY, NUMBER (so-and-so).  This report is sent

when the section is ready to fire (in compliance with the

fire command). The report is sent digitally by pressing the

READY key on the SCA.
c. 

In voice operations, SHOT NUMBER (so-and-so) is

reported after each round has been fired. If, however, the

method of fire is more than one round, SHOT is announced

only after the initial round. For GDU-equipped howitzers,

the report is sent digitally when the section chief presses

the SHOT/RC key once on the SCA.

d. ROUNDS COMPLETE NUMBER (so-and-so) 

is

announced when the final round designated in the method

of fire has been fired. If, however, only one round is to

be fired, ROUNDS COMPLETE will not be reported after

SHOT. 

For GDU-equipped howitzers, the report of rounds

complete (RC) is sent when the SHOT/RC key on the SCA

is pressed a second time. For a GDU-equipped howitzer

to receive subsequent fire commands in any mission, rounds

complete must be transmitted to the FDC.
e. MISFIRE NUMBER (so-and-so) 

is announced when

a misfire has occurred (voice only).
f. 

Ammunition status is reported. The number of rounds

expended, by type and lot number, is reported when requested

by the FDC (voice or per unit SOP).
g. 

Data fired in error are reported. The chief of section

reports to FDC the actual data fired in error; for example,

NUMBER 2 FIRED DEFLECTION (so much).

7-23. STANDARDIZING ELEMENTS

OF THE FIRE COMMAND

Certain elements of fire commands may be standardized after

the tactical situation, weapon, and personnel capabilities,

ammunition status, and enemy counterfire threat have been

considered. As shown in Table 7-1, the following elements

of the fire command may be designated as standard: pieces

to follow, pieces to fire, method of fire, projectile, ammunition

lot, and fuze. If the FDO decides to vary from fire command

standard data, he must administratively cancel the existing

standard and issue the replacement standard data. Only one

set of standard data can be in effect at any particular time.

7-7

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FM 6-50, MCWP 3-1.6.23

Once standard data are placed in effect, the platoon will

fire the standard data unless the fire command specifies

something different.

EXAMPLE

The FDO or platoon leader considers the tactical

situation and the other factors mentioned above and

determines that the fire command elements designated

as standard should be as follows:

Pieces to fire and method of fire: Number 3, 1 round.
Projectile: HE.
Ammunition lot: XY.
Fuze: Quick.

These standards tell the firing battery or platoon that

if not stated in a fire command, the piece to fire will

be Number 3, and the method of fire will be one round,

shell HE, lot XY, and fuze quick.

7-24. EXAMPLE OF FIRE COMMANDS

a. Nonstandard Adjust-Fire Mission. 

In this example,

no standard elements are used. (See Figure 7-4.)

FIRE MISSION, PLATOON ADJUST, NUMBER 3, 1

ROUND, SHELL HE, LOT XY, CHARGE 4, FUZE

QUICK, DEFLECTION 3024, QUADRANT 247, 2

ROUNDS IN EFFECT.

(1) Number 3 is announced as the adjusting weapon.

It fires one round (shell HE, lot XY, fuze quick) with the

announced charge, and at the announced deflection, and

quadrant. The rest of the platoon prepares 2 HE rounds

with fuze quick and follow the fire mission.

(2) The first subsequent fire command is as follows:

DEFLECTION 2978, QUADRANT 218.
Number 3 fires one round (shell HE, lot XY, charge 4, fuze

quick) at the new deflection and quadrant.

(3) The second subsequent fire command is as follows:

PLATOON 2 ROUNDS, DEFLECTION 2950,

QUADRANT 210.

The entire platoon fires two rounds at the announced

deflection and quadrant. END OF MISSION is commanded

as appropriate. At END OF MISSION, an ammunition

update is required as shown in Figure 7-4.

7-6

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FM 6-50, MCWP 3-1.6.23

b. Nonstandard FFE Mission.

In this example, no

standard elements are used:
FIRE MISSION, NUMBER 3 AND NUMBER 4, 3

ROUNDS, SHELL WP, LOT DY, CHARGE 7, FUZE

QUICK, DEFLECTION 2870, QUADRANT 320.

Number 3 and Number 4 each fire three rounds as

commanded. END OF MISSION is commanded as

appropriate, and ammunition expended is updated (see Figure

7-4).
c. Standard Adjust-Fire Mission. 

Elements designated

as standard in this example are Number 3 firing one round

in adjustment, shell HE, lot XY, and fuze quick:
FIRE MISSION, PLATOON ADJUST, CHARGE 4,

DEFLECTION 3024, QUADRANT 247, 2 ROUNDS IN

EFFECT.

(1) Number 3 fires one round (shell HE, lot XY, fuze

quick) with the announced charge, and at the announced

deflection and quadrant. Nonadjusting pieces prepare two

rounds of HE and follow commands. Adjustment continues

as in the first example.

(2) When fire for effect is entered, the commands are:

PLATOON 2 ROUNDS, DEFLECTION 2950,

QUADRANT 210.

(3) The entire platoon fires two rounds of shell HE at

the announced deflection, and quadrant. END OF MISSION

is commanded as appropriate.

Note: 

At END OF MISSION, an ammunition update is

required as illustrated in Figure 7-5, page 7-10.

d. Standard FFE mission.

Elements designated as

standard in this example are Number 3, one round, shell

HE, lot XY, and fuze quick.
FIRE MISSION, PLATOON 3 ROUNDS, CHARGE 4,

DEFLECTION 3111, QUADRANT 400.
Each weapon in the platoon fires three rounds (shell HE,

lot XY, fuze quick) with the announced charge, and at the

announced deflection and quadrant. END OF MISSION

is commanded as appropriate, and ammunition is updated

(see Figure 7-5).

7-9

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FM 6-50, MCWP 3-1.6.23

7-25. RECORD OF MISSIONS FIRED

a. 

The DA Form 4513 or 4513-R is used by each section

to record fire commands (digital or voice), ammunition stock

(on hand, fired, transferred or resupplied), and any

standardized data. After this form has been completed, it

is used primarily for computing remaining tube life on the

DA Form 2408-4. All elements, of this form must be recorded

neatly and accurately.

Note: 

A reproducible copy of DA form 4513-R is located at

the back of this manual.

b. 

The form consists of four basic parts. They are the

administrative

data (to include standard data),

AMMUNITION/FUZES ON HAND, the fire mission data

(to include transfer and resupply) and AMMUNITION

EXPENDED. Each of these parts should have the following

information recorded (see Figures 7-4 and 7-5):

(1) Administrative data

(a) SECTION-howitzer bumper number/position

number in formation.

(b) DATE-date of firing.
(c) PAGE OF-each side of the form represents one

page of the total pages for that days firing.

(d) STND DATA-elements of a fire command

standardized in order to expedite the delivery of fires.

ADJ PIECE-howitzer designated as adjusting

piece (voice commands only) and number of

rounds to be fired.

SH-type of shell used in adjustment.
LOT-designated lot of projectile and propellant.

Lot designators are usually established by the

platoon leader or fire direction officer.
FZ-type of fuze used in adjustment.

(2) AMMUNITION/FUZES ON HAND

(a) On the first line, enter the type of ammunition.
(b) On the second line, list lot designators for projectiles,

propellants, fuzes, and the primer nomenclature. Projectiles and

propellants are recorded separately for separate-loading

ammunition.

(c) On the third line, list the actual count of each.

(3) Fire mission data.

(a) Record fire command elements in this portion unless

they are already standardized.

(b) Record resupply and transfer of ammunition.

(4) AMMUNITION EXPENDED

(a) In this column, record all ammunition expended or

received.

(b) Circle each round shot in a fire mission, and record

the cumulative count. Upon receipt of EOM, subtract total rounds

fired (the last circled number in the column) from the initial or

latest total.

(c) Entries for resupply and transfer of ammunition are

not circled.
c. 

The DA Form 4513 or 4513-R should be turned in

(usually to the GSG, platoon sergeant, or platoon leader)

once every 24 hours for the purpose of updating the DA

Form 2408-4. The unit SOP applies. The PAGE OF block

is completed at this time. The form should be filled out

completely to eliminate errors. The chief of section should

check it periodically for neatness and accuracy,

Note: 

A cumulative count is kept to reduce errors in

deriving totals. Once totals are derived, except those listed

in the AMMUNITION/FUZES ON HAND block, they are

represented by two slashes in the upper left-hand corner of

the block being totaled. When a page is filled out in full, the

totals placed in the AMMUNITION/FUZES ON HAND block

on the next page are the last listed totals. At the end of a

mission or upon resupply, the amounts of ammunition on

hand are totaled on the appropriate line. Thus, a running

count is continually maintained.

7-10

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FM 6-50, MCWP 3-1.6.23

CHAPTER 8

SPECIAL SITUATIONS

8-1. DIRECT FIRE

Direct fire is a special technique that demands a high standard

of training and requires the section to operate as an

independent unit. It should be used only as a last resort.

Considerations for direct fire engagements are discussed

below.

a. Trajectory. 

Trajectory characteristics change with the

range to target and charge fired. The following information

is based on use of charge 7.

Note: 

To produce the highest muzzle velocity and a

flat trajectory, the maximum charge should always be

used for direct fire.

(1) 0 to 400 meters. This is the most accurate range

at which to engage a target with direct fire during combat,

because the trajectory is flattest.

(2) 400 to 1,500 meters. In this zone, the trajectory is

.

flat enough to allow direct estimation of range without actual

bracketing of the target.

Range changes in 50-meter

increments give the best results.

(3) 1,500 to 2,500 meters. Hits are only reasonably

possible in this zone. The bracket method of adjusting will

probably be required to obtain a hit.

(4) Over 2,500 meters. Direct fire is not effective.

b. Types of Targets. 

The most likely direct-fire targets

are vehicles and/or dismounted personnel. Vehicles are

engaged as point targets. Personnel are engaged as area

targets. Direct-fire priorities should be as follows:

Vehicles at short ranges threatening to overrun the

position.

Stationary vehicles covering the advance of other

vehicles.
Command and control vehicles.

c. Ammunition

(1) Shell/fuze combination used against armor and

vehicular targets are as follows:

105mm— Shell high explosive plastic-tracer

(HEP-T); shell HE with impact, mechanical time,

or variable time fuzes set for superquick action; and

shell WP with impact or mechanical time fuze set

for superquick action.
155mm— shell HE with impact, mechanical time, or

variable time set for superquick action and shell WP

with impact or mechanical time fuze set for

superquick action.

Note: 

WP projectiles can be used effectively to

ignite immobilized vehicles.

Smoke and WP

projectiles can be used to obstruct the vision of

vehicle drivers and tank gunners and serve to
disorient them.

(2) Shell/fuze combinations used against personnel are

as follows:

105mm-antipersonnel (APERS-T) and shell HE

with impact (set for delay action), mechanical time,

or variable time fuzes (set for superquick action)

fuze.

155mm-shell HE with impact (set for delay action),

mechanical time or variable time fuzes (set for

superquick action) fuze.

Note: 

When used against personnel, shell HE with

impact fuze (delay action) is fired at a point 10 to 30
meters in front of the target to achieve the best
effects.

8-2. DIRECT FIRE SIGHTING METHODS

The three 

primary methods of sighting used in direct fire

are as follows:
a. Two-Man, Two-Sight. This method is best for all

weapons except the 105-mm howitzer M119. The gunner

establishes lead with the pantel, and the AG establishes

elevation with the direct fire telescope. This is the fastest

and most accurate method of sighting. It permits the AG

to check the direction of lead. The reticle in the direct-fire

telescope must be level. A canted reticle in the direct fire

telescope will prevent satisfactory direct fire on moving

targets because an unacceptable range error is introduced

when lead is changed.

b. Two-Man, One-Sight. 

The gunner establishes lead with

the pantel, and the assistant gunner sets elevation on the

elevation quadrant at the command of the chief of section.

This method is not effective when the target is moving on

other than flat terrain.

8-1

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FM 6-50, MCWP 3-1.6.23

c. One-Man, One-Sight. 

This method is least desirable

and should not be used unless absolutely necessary. The

gunner lays for lead and elevation with the reticle of the

pantel. This method should not be used if the target is

moving or on a steep slope.

8-3. DIRECT FIRE LAYING METHODS

The two primary methods of laying for direct fire are

discussed below.
a. Reticle Laying. 

The gunner maintains lead by placing

the vertical hairline the proper number of mils ahead of the

point of aim on the target (Figure 8-1).

b. Central Laying. 

The gunner sets the lead in mils on

the azimuth micrometer scale of the pantel and maintains

the vertical hairline of the reticle on the center of the target

(Figure 8-2). There is a modification on the knob of the

M100-series pantel called a click sight. It permits the gunner

to set off lead in 5-mil increments, by sound or feel, without

removing his eye from the sight.

8-4. COMMANDS FOR DIRECT FIRE

a. 

The platoon leader/XO or BC will direct the engagement

of targets by certain sections using verbal commands.

Normally, individual section commands for direct fire are

given by the howitzer section chief. The commands include

the following:

A warning order - TARGET (so-and-so).
General direction to the target 
- LEFT FRONT.

8-2

Lead in mils (how to determine lead is explained in

the weapon manual) - LEAD, RIGHT 5.

Range to target-RANGE 800.
Method of 
fire-FIRE AT WILL.

b. 

The shell, fuze, and charge to be fired should be

standardized to save time. If a shell-fuze combination other

than the standard is desired, the command SHELL

(so-and-so), 

with time (if applicable), is given after the

direction to target.
c. 

The howitzer section chief gives subsequent commands

based on the observed effects.

(1) Change in lead. During adjustment, the lead in mils

is changed to a new total lead command.

EXAMPLE

The initial fire command was LEAD LEFT 5. After

spotting the burst, the section chief decides a lead of 10

will hit the target. His subsequent command is LEAD

LEFT 10.

(2) Change in range. During adjustment, the range is

increased by the command ADD (so many meters) and is

decreased by the command DROP (so many meters).

Another option is that the section chief announces a new

range based on the desired increase or decrease in range to

hit the target. Unit SOPs will dictate which technique to

use.

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FM 6-50, MCWP 3-1.6.23

d. 

When commands for direct fire are issued, firing battery

personnel must ensure that direct-fire engagements do not

result in fratricide. This is the particular responsibility of

the howitzer crew, section chief, FDO, platoon leaders, and

platoon sergeants in a platoon-based unit and of the XO,

chief of tiring battery, and GSG in a battery-based unit.

(See AR 385-63 on minimum engagement ranges.)

8-5. EMERGENCY BORESIGHTING

a. 

Boresighting is the only means a gunner has of ensuring

that the optical axis of his sights are parallel to the tube of

the weapon. The weapon should be boresighted in the

following cases:

Anytime the sight has been subjected to any shock

other than tiring.

Before firing in a new firing position (verify).
Anytime the howitzer fires inaccurately for no apparent

reason.

b. 

The primary methods of boresighting are:

Distant aiming point.
Test target.
Standard angle.

c. 

When time is not critical and the tactical situation permits,

use of the test target may be preferred over the DAP method

because of its accuracy.
d. 

Boresighting methods are discussed in detail in the

applicable weapon manuals. The following paragraphs

describe several boresighting techniques that may be used

if, for some reason, one of the primary methods is not possible.

8-6. COLLIMATOR METHOD OF

BORESIGHTING

The collimator may be used to boresight weapons.

Procedures are as follows:
a. 

Prepare the weapon for boresighting in the same manner

as for the DAP method.
b. 

Place the collimator about 20 feet in front of the tube.

c. 

Sight through the tube and align the 0 of the collimator

with the vertical muzzle boresight string.
d. 

With the pantel, sight on the collimator and match the

numbers on the reticle pattern of the sight with the numbers

on the collimator. The reading should be as follows:

3200 on the azimuth scale of the M 100-series sight.

0 on the slip scale of the M12-series sight.

Note: 

This method may not work with the

Ml09A31A6 or Ml98 howitzers. Because of the

length of the tubes on these howitzers, the numbers

in the collimator may not be visible during the

alignment portion (paragraph c above) of the

boresighting process.

8-7. STANDARD ANGLE METHOD OF

BORESIGHTING

For the M101A1, the standard angle must be established

during the conduct of a fire control alignment test. The

procedures are outlined in the applicable weapon manuals.

To boresight by the standard angle method, do the following:
a. 

Establish the recoiling parts in the same relationship to

the nonrecoiling parts as they were when the standard angle

was established.
b. 

Place a pin in the left witness mark on the muzzle.

c. 

Install the parallax shield.

d. 

Set the standard deflection angle on the telescope.

e. 

Using a tested gunner’s quadrant, set the standard

elevation angle.
f. 

Match all standard angle scribe lines.

g. 

If the weapon is out of boresight, do not disturb the

bubbles. Adjust the vertical hairline onto the junction of

the pin and the muzzle.

Note: 

As soon as possible, the boresight should be

verified by a more accurate means.

8-8. AIMING CIRCLE METHOD OF

BORESIGHTING

a. 

Set up the aiming circle approximately 30 to 50 meters

in front of the weapon (Figure 8-3, page 8-4).
b. 

Insert the boresight disks and strings in the cannon.

c. 

With the upper motion of the aiming circle, set off

0000 (for M12-series sights) or 3200 (M100-series sights).
d. 

Align the cannon bore on the aiming circle, and center

the cross-level bubble of the pantel.
e. 

With the lower motion of the aiming circle, align the

vertical hairline on the center of the cannon bore.

8-3

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FM 6-50, MCWP 3-1.6.23

f. 

With the upper motion of the aiming circle, align the

g. 

The gunner sets the announced reading on the pantel.

vertical hairline on the pantel of the weapon. Read the

He then adjusts the pantel by using the tangent screws, or

instrument reading (angle from center bore to pantel) to the

the boresight adjustment shaft, until his sight picture is

weapon.

centered on the lens of the aiming circle.

8-4

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FM 6-50, MCWP 3-1.6.23

CHAPTER 9

COMMUNICATIONS

9-1. COMMUNICATIONS EQUIPMENT

The cannon battery or platoon uses both radio and wire

equipment. Either system will become primary or secondary,

depending on the tactical situation and the availability of

equipment.

There are advantages and disadvantages

associated with each. For example, radio permits mobility

and speed but is susceptible to enemy electronic warfare

(EW). Wire lines are more immune to enemy EW, but they

inhibit rapid movement and speedy installation. Hence, the

strength of one becomes the weakness of the other.

Therefore, it is reasonable to view the battery or platoon

communications (comm) system as that which makes the

best use of the radio and wire resources available at any

given time. We must always strive to have a system

redundant to the one being used, be it radio or wire. Ideally,

it would be best to rely first on radio during displacements

and initial site occupations. Then, if time permits, install

and operate on wire lines. If radios are unavailable, or

unusable, a wire system is necessary. Accordingly, the

diagrams and system configurations which follow provide

practical and realistic ways of establishing battery commo

systems, depending on which TOE a unit uses.

9-2. BATTERY COMMUNICATIONS

SECTION

a. 

To help the battery commander meet communications

requirements, a comm section is authorized at the battery

level.

This section gives battery personnel technical

assistance in the installation, operation, and maintenance of

the battery comm system.

Battery personnel share

responsibility for installing, operating, and maintaining the

battery comm system.

b. 

The battery comm chief advises the commander on

communications matters. The two wiremen help install and

maintain the intrabattery wire system and wire equipment.

The comm chief’s specific responsibilities are as follows:

(1) Provide communications training to battery

personnel and technical assistance for communications

training in the unit.

(2) Advise the BC on communications considerations

during selection of positions.

(3) Supervise the maintenance of comm equipment in

the battery.

(4) Coordinate with the battalion comm chief on matters

of personnel, communications security (COMSEC) materials,

equipment, parts, maintenance support, and communications

training.

9-3. BATTERY WIRE SYSTEM

a. 

Presently, the FA battery or platoon relies on wire to

meet its internal communications needs. Three DR-8s are

issued to each howitzer section so the battery can have a

separate voice, digital, and advance party capabilities.
b. 

There are changes to the wire terminals used in the

battery wire system. The SB-16 is no longer recommended

for digital communications. The terminal strip TM-184

provides a cleaner, more reliable digital signal. The TM-184

(NSN 5940-00-238-8493) is a class IX item and can be

procured through the unit supply system. Four TM-184s

will be required to install the battery or platoon wire system.

One will serve as the voice wirehead, one as the digital

wirehead, and one for an advance party capability. The

fourth connects battalion wire lines.

Two additional

TM-184s are required for the second platoon in a platoon-

based battery.

(1) Advance party. The advance party wire system

(Figure 9-1) provides immediate voice communication upon

arrival of the main body, between each howitzer, the aiming

circle, and the FDC.

(a) When the advance party arrives at a new location,

a designated platoon representative places a voice wirehead

(TM-184) in the position area, usually near the platoon center

behind the gun line. This will allow personnel to troubleshoot

most of the wire system from behind the gun line.

(b) Using a DR-8 (¼-mile reel), the gun guides

connect the running end of each wire line to the appropriate pair

of line binding posts on the voice wirehead. After this

connection is made, the wire lines are tied off to a stake next to

the voice wirehead and are tagged. Each gun guide then routes

the wire from the voice wirehead to his gun position and connects

it to the line binding posts on his telephone set TA-312 or

headset-chestset, sound powered H-200. It is advisable to route

wire lines to a stake forward of the gun line, as illustrated in Figure

9-1, to avoid wire line damage by vehicles moving in with the

main body. However, the chosen wire line route will be

dictated by terrain and available wire.

9-1

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FM 6-50, MCWP 3-1.6.23

(c) The FDC representativealso installs a wire line from

the voice wirehead to the FDC position by using a DR-8. The

running end of the wire line is connected to the appropriate pair

of binding posts on the voice wirehead and tied off to a nearby

stake and tagged. The wire line is then routed to the vicinity of

where the FDC will be positioned and is connected to a TA-312,

H-200, or an AN/GRA-39.

(d) To complete the voice wire system, a battery or

platoon representative installs a wire line to the aiming circle

from the voice wirehead. After this circuit is completed by

installation of a telephone set TA-312, or H-200, the telephone

system will allow the howitzers to be laid when the main body

occupies the firing position.

(2) Main body occupation. Soon after the main body

is in position, a second wire system is installed for digital

communications.

(a) A second TM-184 (digital wirehead) is also placed

near the battery or platoon center behind the gun line. The

procedure for installing this system is identical to that used by

the advance party, except the wireline is connected to the GDU

at the howitzer and to the BCS in the FDC (Figure 9-2). In the

howitzer, the wire line is connected to the BCS binding posts

(labeled BCU) of the case assembly (Figure 9-3). The wire line

at the FDC is routed into the vehicle and connected to the wire

line adapter of the BCS (Figure 9-4, page 9-4). Stakes should be

used at the howitzer and the FDC to secure incoming wire lines

to reduce damage to the wire system by moving vehicles and

personnel. Again, if terrain and available wire permit, the digital

system should be routed to the front of the gun line to minimize

system damage.

CAUTION

Avoid any ringing-type comm device on the digital

line, as they have the potential to destroy the GDU

case assembly.

(3) Complete system. If time and assets permit, a wire

line can be installed as necessary between the BCS of the

two platoon FDCs by using an RL-27 and RL-159 (Figure

9-5, page 9-5). This wire line can be used as necessary to

hand off digital fire missions between FDCs. As time and

mission allow, SB-22 switchboards can be installed in each

platoon and connected by wire line to a battery command

switchboard (SB-22) providing voice communications. In

battery based operations (Figure 9-6, page 9-6), only a battery

command switchboard is installed. Additional voice or

digital capability can be provided by a battery wirehead that

interfaces with battalion voice and digital wire lines. In

most cases, external communications rely primarily on radio

communications (and mobile subscriber equipment). The

extent to which wire is installed and lines are improved or

protected depends on the anticipated time the firing unit

will stay in position before moving again.

9-2

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FM 6-50, MCWP 3-1.6.23

9-3

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FM 6-50, MCWP 3-1.6.23

c. 

All wire lines should be identified by tagging them

(O&I) element is the net control station (NCS). The battery

individually at each end as outlined in TC 24-20 and at

each stake. This facilitates troubleshooting the wire system.

Wire tags should be prepared and labeled in accordance

with the unit signal operating instructions (SO1) and SOP.

9-4. BATTERY RADIO NET STRUCTURE

The firing battery in a direct support (DS) battalion operates

in two external radio nets and one internal radio net. Figure

9-7, page 9-7, shows the battery (btry) radio net structure.

Listed below are the radio nets in which the battery operates

and a description of how each net is used.
a. Battalion Command (Cmd) Net (FM-Voice). 

This is

a secure net used for command and control and for intelligence

information. The battalion (bn) operations and intelligence

commander, first sergeant, platoon leaders, platoon sergeants,

platoon FDCs and the ammunition sections operate in this

net.
b. Battalion Fire Direction Nets (FB1, FD2, FD3)

(FM-Digital). 

These are tactical fire direction (FD) nets

that are assigned one to each firing battery. The Bn FDC

is the NCS for these nets. The assigned net (FD1, FD2, or

FD3) is used to pass digital traffic. It may be converted to

a voice net to fit operational needs. Each platoon FDC

operates in this net and communicates digitally with the

battalion FDC by using the BCS. The platoon FDC can

also use this net as directed to communicate with the company

fire support headquarters, forward observers, battalion fire

support section, combat observation/lasing teams, aerial

observers, and Firefinder radar sections.

9-4

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FM 6-50, MCWP 3-1.6.23

9-5

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FM 6-50, MCWP 3-1.6.23

9-6

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FM 6-50, MCWP 3-1.6.23

c. Battery Command/Fire (CF) Net (FM-Voice

and/or Digital).

With the fielding of the small unit

transceiver (SUT) AN/PRC-68 or AN/PRC-126 and the radio

set

single channel-ground and airborne radio system

[SINCGARS]), each FA firing battery will have its own

internal radio net.

(1) The L-edition TOE authorizes two AN/PRC-68s or

AN/PRC 126s per howitzer section (one in the howitzer

and one in the ammunition resupply vehicle, one per FDC,

one per platoon leader, and one for the battery commander.

(2) The AN/PRC-68 or AN/PRC-126 can receive

operating power from either the battery source or from a

vehicular power system.

In the hand-held mode, the

AN/PRC-68 or AN/PRC 126 is powered by a 15.4 volt dry

battery (BA-1588) that provides 24 hours of continuous

operation. To operate the AN/PRC-68 or AN/PRC 126 with

vehicular power, an amplifier-power supply OG-174 is

required.

The OG-174 allows the AN/PRC-68 or

AN/PRC-126 to be mounted inside a vehicle, interfacing

with the vehicle intercom. It provides an external antenna

(Figure 9-8).

(3) Once the AN/PRC-68s or AN/PRC-126s are

connected to the BCS and GDUs in the FDC and howitzers,

respectively, the Battery CF Net can be used to pass digital

traffic between the FDC and the howitzer sections. Once

quality digital communications is established, voice

communications should be discontinued and all headsets may

be removed.

9-5. AN/PRC-68 AND AN/PRC-126

PLANNING CONSIDERATIONS

The AN/PRC-68 or AN/PRC-126 can be employed in a

variety of tactical applications.

However, limitations

sometimes make it less than ideal.

Therefore, wire

communications should always be established if logistics,

time, and tactical constraints permit. The AN/PRC-68 or

AN/PRC-126 with OG-174 gives the FA cannon battery or

platoon the capability to transmit digital as well as voice

communications internally.

Without the OG-174, the

PRC-68 or AN/PRC-126 is used routinely for voice

communications only in the hand-held mode. The following

planning considerations are provided for use of the SUT:
a. 

The battery comm chief can set the AN/PRC-68 or

AN/PRC-126 internally on one base frequency.

Any

frequency change will be a time-consuming process.

Therefore, units should request a fixed, sole user frequency

to be included in the SOI for the battery CF net.
b. 

The use of the AN/PRC-68 or AN/PRC-126 may need

to be tailored to a particular mission. Their use during

convoys, ammunition resupply, hip shoots, and advance party

and main body operations may warrant a change in

assignment of these radios.
c. 

Radio-electronic combat may preclude the use of the

radio because of jamming.

d. 

Mutual interference between friendly units may preclude

use of the radio.
e. 

Alternate frequencies to be used in case of jamming

must be identified.

9-7

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FM 6-50, MCWP 3-1.6.23

system will malfunction, especially in wet weather or in

9-6. BCS-TO-GDU COMMUNICATIONS

The BCS-to-GDU link is the location of the most frequent

problems. This area requires constant command attention

if the maximum benefit is to be derived from the entire

system. The following are the most common errors reported

by or recommendations received from units worldwide:

a. BCS-GDU Wire Connection.

(1) Wire must be perfect.
(2) There must be a dedicated GDU wire with no splices.
(3) WD-1 was never meant for digital communications.

One improper splice or one short may knock the entire system

out. (Acquire copper wire WF 16U, NSN 6145-00-910-8847,

for use with the GDUs.)
b. Gun Assemblies for Deflection and Quadrant. 

There

must be enough slack in wire lines for shifting trails.

Otherwise, wires or assemblies may be damaged.
c. Grounding.

(1) The case assembly on a howitzer must be properly

grounded according to TM specifications. Otherwise, the

9-8

early-morning dew.

(2) All wires and cables must be installed according to

exact TM specifications.
d. Switchboard Use. 

Do not use an SB-22 or a similar

device that requires a male end metal connector. Use a

TM-184 or TM-125 type of terminal device.

e. GDU Power for Towed Unit. 

For GDU power, use

a plug-in device to connect with the prime mover. Do not

use a clamp connector to the vehicle battery since this will

damage or destroy batteries and/or the GDU.

f. Mounts.

All locally fabricated mounts should be

inspected by comm technicians for proper power hookup

and grounding.
g. Wire Setup Within the Position.

(1) A loop wire system from BCS to GDUs does not

work. 

The vast and continuous amount of traffic in the

system causes a loop to overload and malfunction or the

guns will receive improper data.

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