FM 4-55 Seacoast Artillery Service of the Piece 12-Inch Mortar (Fixed Armament) 1943

MHI I Shl Ij l FM 4-55MHICopy 3

WAR DEPARTMENT

COAST ARTILLERYFIELD MANUAL

SEACOAST ARTILLERY

SERVICE OF THE PIECE

12-INCH MORTAR (FIXED ARMAMENT)

RFI 4-55c

RESTRICTED

COAST ARTILLERY FIELD MANUAL

SEACOAST ARTILLERY



CHANGES WAR DEPARTMENT,No. 1 WASHIrNGTON, April 23, 1943.FM 4-55, May 15, 1940, is changed as follows:

SECTION VI1½ (ADDED)

DESTRUCTION OF MATEtRIEL

U 53. GENERAL PBINCPLES.-a. Tactical situations may arisewhen, due to limitations of time or transportation, it will be-come impossible to evacuate all equipment. In such situationsit is imperative that all materiel that cannot be evacuated bedestroyed to prevent-

(1) Its capture intact by the enemy.(2) Its use by the enemy, if captured, against our own or

allied troops.b. The working principles to be followed are:(1) Methods for the destruction of materiel subject to capture

or abandonment in the combat zone must be adequate, uniform,and easily followed in the field.

(2) Destruction must be as complete as the available time,equipment, and personnel will permit. If thorough destructionof all parts cannot be completed, the most important featuresof the matdriel should be destroyed, and parts essential to theoperation or use of the materiel, and which cannot be easilyduplicated, ruined or removed. The same essential partsmust be destroyed on all like units to prevent the enemy'sconstructing one complete unit from several damaged ones by"cannibalization."

(3) The destruction of materiel subject to capture or abandon-ment will be undertaken only when ordered by the harbor defenseor higher commander.

c. To accomplish adequate and uniform destruction of materiel,it is essential that-

522249°--43

COAST ARTILLERY FI - AANUAL

(1) All echelons prepare plans for the destruction of materielin the event of imminent capture. Such plans must be flexibleenough to make allowance for variations in available time, equip-ment, and personnel.

(2) All echelons be trained to effect the desired destruction ofmateriel issued to them. Training will not involve the actualdestruction of ma tdriel.

d. Certain of the methods outlined require special tools andmaterials, such as TNT and incendiary grenades, which normallymay not be items of issue. The issue of such special tools andmaterials, the materiel for which issued, and the cpnditions underwhich destruction will be effected are command decisions in eachcase, according to the tactical situation.

* 54. PRIORITY 01 DESTRUCTION.-a. Destruction should be accom-plished in the following priority:

(1) Tube, breech, and recoil mechanism.(2) Carriage.(3) Power equipment.(4) Sights and observation instruments.(5) Plotting room equipment.(6) Ammunition.(7) Fire control and observation stations and ammunition

magazines.b. In the event of imminent capture, everything that could be

of possible use to the enemy should be destroyed. If evacuationis probable, all sights, optical instruments, and other valuablesmall items should be evacuated.

* 55. TUnE.-a. General.-The selection of a method of demoli-tion will depend on the tactical situation and the materials avail-able. The methods for the destruction of the tube are presentedin the order of their effectiveness.

b. Demolition by unfuzed HE shell and either M9A1 ATgrenade or M6 AT rocket.-(1) Remove the recoil cylinder plug.It is not necessary to wait for the recoil fluid to drain completelybefore firing the piece as in (4) below.

(2) Lay an armed (safety pin removed) M9A1 AT grenade,HE, or M6 AT rocket in the tube about 6 inches in front of theprojectile (in (3) below) with the ogive nose end toward theshell. The grenade or rocket must be centered in the tube, usingeither a wooden adapter or a wad of waste.

(3) Place an unfuzed, boostered, point-detonating HE shelland propelling charge in the gun and close the breech.

2

12-INCH MORTAR (FIXED ARMAMENT)'

(4) Fire the gun electrically if possible; if not, use a lanyardat least 100 feet long. The person firing the piece should beunder cover in rear of the piece and about 200 off the line of fire.

(5) When using this method, the danger zone is about 500 yardsin radius.

c. Demolition by TNT blocks and HE s8hell.-Remove therecoil cylinder drain plug. Ram an HE shell (without basefuze) into the forcing cone, place 120 1/½-pound TNT blocks inthe chamber of the gun, and close the breech. Detonate theTNT with a detonating cord routed through the primer vent.A sufficient length of safety fuze should be used to permit per-sonnel to reach cover.

d. Demolition by TNT blocks.-(1) Remove the recoil cylinderdrain plug. Insert 120 '/2-pound TNT blocks in the chamberand close the breechblock. Plug the muzzle end of the tubetightly with earth to a distance of approximately 3 feet fromthe muzzle. Detonate the TNT charge by means of a detonat-ing cord routed through the primer vent.

(2) The firer should be under cover. The danger zone is about500 yards.

(3) For instructions on the wiring and firing of TNT, seeFM 5-25.

e. Demolition by incendiary grenades.-If evacuation is immi-nent and it is desired to accomplish demolition without telltaleexplosions, the following method should be used: Place 15 to 25unfuzed M14 incendiary grenades in the chamber. They shouldbe placed on their sides and stacked one on top of another. Closethe breech. Equip another incendiary grenade with a 15-secondBickford fuze, ignite it, and throw it in the muzzle. Elevatethe gun quickly to its maximum elevation. The metal from thegrenades will fuse with the interior of the breechblock, makingit impossible to open the breech.

* 56. BREECH.-Any of the above methods for destroying the tubeshould also destroy the breech; but if the method selected doesnot, a heavy sledge may be used to render the breech useless.

* 57. RECOIL MECHANISM AND CARImAGE.-The method explainedin paragraph 55b, c, or d for destroying the tube will destroythe recoil mechanism and carriage if the drain plug on therecoil mechanism is opened, allowing the recoil fluid to drainbefore detonating the TNT charge.. It is not necessary to wait

3

COAST ARTILLERY FIELD 3MANUAL

for the recoil fluid to drain completely before detonating thecharge.

* 58. POWER EQUIPMENT.-All auxiliary power equipment shouldbe rendered useless. Electric motors and generators can mosteffectively and easily be put out of operation by injuring thefield or armature windings. If time is available, the motor shellmay be broken with a sledge and the coils ruined with a crow-bar. If time is short, a small-arms bullet may easily be directedinto the coils through the air vents in either end bell, but careshould be taken to see that nobody is in the path of a possiblericochet. Switch panels, sockets, plugs, and fuse or circuit-breaker panels should be smashed with a sledge or ax.

* 59. SIGHTS AND OBSERVATION INSTRUMx-ENTS.-Sights and ob-

servation instruments should be evacuated if possible. If theycannot be carried away, they should be smashed thoroughly.

* 60. PLOTTING ROOM EQUTIPMENT.-All boards and instrumentsshould be smashed and burned if possible. Data transmittersland all communication equipment should be smashed.

· 61. AMMUNITION.---. Projectiles.-Projectiles are stackedhorizontally with ogive ends pointing in the same direction.Remove the fuze from the center shell in the top row of eachpile. Pack a detonating cap, with detonating cord attached, nextto the booster in each center shell and detonate. The dangerzone is at least 200 yards. Shells standing on their bases can-not be destroyed satisfactorily by sympathetic detonation.

b. Powder.-Separate loading propelling charges can be de-stroyed best by burning. This is accomplished most effectivelywhen the charges are out of their containers or the containers aresplit.

[ 62. FIRE CONTROL AND OBSERVATION STATIONS AND AMMUNI-

TION MAGAZINES.--a. These installations can best be destroyedby demolition with TNT.

b. See FM 5-25 for demolition planning and execution.

[A. G. 062.11 (3-26-43).] (C 1, Apr. 23, 1943.)BY ORDER OF THE SECRETARY OF WAR:

G. C. MARSHALL,

OFFICIAL: Chief of StaffJ. A. ULIO,

Major General,The Adjutant General.

U. S. GOVERNMENT PRINTING OFFICE: 1943

FM 4-55

COAST ARTILLERYFIELD MANUAL

SEACOAST ARTILLERY



Prepared under direction of theChief of Coast Artillery

UNITED STATES

GOVERNMENT PRINTING OFFICE

WASHINGTON: 1910

For sale by the Superintendent of Documents. Washington. D. C. - Price 15 cents

WAR I)EPARTMENT,WASHINGTON, May 15, 1940.

FM 4-55, Coast Artillery Field Manual, Seacoast Artillery,Service of the Piece-12-inch Mortar (Fixed Armament)is published for the information and guidance of allconcerned.

[A. G. 062.11 (4-6-40).1

BY ORDER OF THE SECRETARY OF WAR:

G. C. MARSHALL,Chief of Staff.

OFFICIAL:

E. S. ADAMS,Major General,

The Adjutant General.

TABLE OF CONTENTS

SECTION I. GENERAL. Paragraph PageScope ____________-_--_______.... 1 1References _______________________ 2 1

II. ORGANIZATION.Gun section ___________________-- 3 1Mortaf squad _____.-- ___----_____ 4 3Ammunition squad ------------ _-- 5 3Foirmation _______________________ 6 3

III. DUTIES OF PERSONNEL.Battery executive_ _______________ 7 3Assistant battery executive-------- 8 4Pit commander (chief of section)--__ 9 4Chief of mortar squad_____-_----- 10 6Azimuth setter_ -_________________ 11 7Elevation setter__________________ 12 7Chief of breech-___________________ 13 7Azimuth recorder_________________ 14 8Elevation recorder_________________ 15 8Chief of ammunition_____________ 16 8Ammunition squad_______________ 17 9Azimuth display board operator____ 18 10Elevation display board operator__ 19 11Artillery mechanics _____________- 20 11

IV. NOTES ON THE SERVICE OF THE PIECE.General__________________________ 21 11Cover posts_______________________ 22 12Stand fast _______-_______________ 23 13Operation of breech ____________- 24 13Service of ammunition__________-- 25 14Loading__________________________ 26 15Pointing and firing __________---- 27 15Drill with dummy ammunition___ 28 16Posting data______________________ 29 17Butterfly net--___________________ 30 17Protection from concussion_______ -1 17Loading position limits ______---- 32 18

V. SAFETY PRECAUTIONS.General__________________________ 33 18Cease firing______________________ 34 18Firing mechanism_________-------- 35 18Lanyard__________________________ 36 19Primers _________________________ 37 19Fuzes __…__________________________ 38 20Service of powder charges_____--- 39 20Sponging powder chamber_______- 40 20Cover for gun section____________ 41 20Misfires __________________________ 42 20Equalizing pipe ___--_____-- __---- 43 21

III

TABLE OF CONTENTS

SECTION VI. CARE AND ADJUSTMENT OF MATtERIEL. Paragraph PageSponging solution-__._________-___ 44 21Care of bore __-__________________ 45 22Care of carriage and breechblock__ 46 22Filling recoil cylinders____________ 47 23Assembling and adjusting obturator_ 48 23Firing 'mechanism________________ 49 24To test lanyard safety device _-___ 50 25To, test elevation friction device___-- 51 25Technical information on mortar

carriages ......................._______ 52 26VII. DRILL TABLE - -_____________________ __ 26

APPENDIX. List Of References -------------------- 27

IV

FM 4-55

COAST ARTILLERY FIELD MANUAL

SEACOAST ARTILLERY



(The matter contained herein supersedes TR 435-255, Decembe5-24, 1924, including C1, January 2, 1929.)

SECTION I

GENERAL

· 1. SCOPE.-a. This manual prescribes the service of thepiece for the 12-inch mortar, fixed armament. The duties ofthe members of the gun section in the service of the pieceare contained in section III and in the drill table in sectionVII.

b. The service of the piece prescribed herein is intendedas a guide for the battery commander. Changes in the detailsof the service of the piece may be made to meet local con-ditions.

c. The following combinations of mortars and carriagesmay be found in service: M1890MI mortar on M1896MI car-riage, M1890MI mortar on M1896MII carriage, M1912 mortaron M1896MIII carriage, and M1908 mortar on M1908 carriage.The drill in this manual is for use with all of these combina-tions of mortar and carriage.

[ 2. REFERENCES.-The references listed in the Appendixshould be consulted, especially those pertaining to ammuni-tion and to the operation, care, and maintenance of mat6riel.

SECTION II

ORGANIZATION

· 3. GUN SECTION.-Each emplacement of two mortars ismanned by a gun section consisting of a pit commander, two

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3 COAST ARTILLERY FIELD MANUAL

Artillery Mechanic

(a a

0 CHief of Ammunition

o

Elevotion RecordeQ O0 AzimuthRecorder xElevation Setter0 0 Azimuth Setter 0

ZO Chief of Squod

3O S

Elevation Re-corder 0 0 Azimuth RecorderElevationSetter 0 0 Azimuth Settero Chief of Squad

Elevation Display Az. Display BoardBoard Operator Y Operator

30$A Chief of Section' (Pit Commonder)

FIGURE 1.-Formation of the gun section.

NorE.-Nos. 26 to 31, inclusive, are for war strength organizationonly.

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12-INCH MORTAR (FIXED ARMAMENT) 3-7

mortar squads, an ammunition squad, and two display boardoperators. The war strength of the gun section is 57 enlistedmen; the peace strength is 51 enlisted men.

* 4. MORTAR SQUAD.-At both peace and war strength, eachmortar squad (17 enlisted men) consists of a chief of squad,an azimuth setter, an elevation setter, an azimuth recorder,an elevation recorder, and 12 cannoneers, numbered from 1to 12, inclusive.

· 5. AMMuvNmrrON SQuAD.-At peace strength, the ammunitionsquad consists of a chief of ammunition and 13 cannoneers,numbered from 13 to 25, inclusive. At war strength, theammunition squad has six additional cannoneers, numberedfrom 26 to 31, inclusive. The squad is divided by its chiefinto details for the service of powder and projectiles.

* 6. FORMATION.-The gun section assembles in two rankswith 4 inches between files and 40 inches between ranks(fig. 1). The post of the chief of section (pit commander) isin the front rank, 1 pace to the right of his section. Theartillery mechanics, members of the maintenance section,form on the left of the first and second gun sections.

SECTION III

DUTIES OF PERSONNEL

* 7. BATTERY EXECuoiVE.-a. The battery executive com-mands the firing section of the battery and is in charge ofthe emplacements. He is responsible to the battery com-mander for-

(1) Technical handling of the mortars.(2) Training and efficiency of personnel of the firing

section.(3) Condition of mat6riel under his charge.(4) Observance of all safety precautions pertaining to the

service of the piece.(5) Police of the emplacements.b. He supervises preparation of the armament for firing.c. He inspects the mat6riel under his charge and personally

verifies the adjustment of all pointing devices as frequentlyas is necessary to insure accuracy. He or the assistant bat-

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7-9 COAST ARTILLERY FIELD MANUAL

tery executive tests all circuits and firing devices before eachdrill or firing, paying special attention to safety features.

d. He receives the reports of the pit commanders and re-ports to the battery commander, "Sir, - pit (pits) in order,"or reports defects he is unable to remedy without delay.

e. If it becomes apparent that one of the mortars will notbe laid in time, he gives to that squad the command: NO. -TAKE COVER. If it becomes apparent that neither pieceof an emplacement will be laid in time, he commands:RE-LAY and reports his action to the battery commander.When one or more pieces are laid and all details have takencover, he closes the safety switch (if firing by electricity)and reports or signals to the battery commander, "- pit(pits) ready." If for any reason he desires to hold fire forone firing interval, he commands: RE-LAY and reports hisaction to the battery commander.

f. When the mortars are equipped for firing by electricity,they are fired by the battery executive upon receipt of thesignal from the battery commander. When the lanyard isused, the battery executive commands: FIRE upon receiptof the signal.

g. At the conclusion of the drill or firing, the battery execu-tive commands: REPLACE EQUIPMEINT, inspects the em-placements, and reports to the battery commander.

1 8. ASSISTANT BATTERY EXECUTIVE.-The assistant battery

executive performs the duties of the battery executive in-sofar as they pertain to the emplacement or emplacementsto which he is assigned.

*9. PIT COMMANDER (CHIEF OF SECTION).-a. The pit com-mander (noncommissioned officer) is in command of the gunsection. He is responsible to the battery executive for thetraining and efficiency of the personnel of his section, for thecondition of the mat6riel under his charge, and for the policeof the emplacement to which assigned.

b. He supervises the service of the piece and the service ofammunition at his emplacement and personally directs thework of care and preservation at the emplacement.

c. He gives the command DETAILS, POSTS, when the sectionarrives at the emplacement and supervises the procuring of

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12-INCH MORTAR (FIXED ARMAMENT) 9

equipment. After all details have reached their posts (fig. 2),he commands: EXAMINE GUN. He then makes an inspec-tion of the mortars, carriages, and other mat6riel, payingspecial attention to the recoil cylinders, firing mechanisms,safety devices, and the oiling of the various bearings. Hereceives the reports of the chiefs of squads and reports to thebattery executive, "Sir, - pit in order," or reports defects heis unable to remedy without delay.

d. When necessary to verify the section, he commands:CALL OFF. The cannoneers of the section call off their titles

0

FIGURE 2.-DETAILS, POSTS.

or numbers in succession, beginning with the unnumberedmembers of the section proper, followed by the squads inorder. The squads call off successively from right to left,beginning in each squad with the unnumbered cannoneersfollowed by the numbered cannoneers in order. (See fig. 1.)

e. At the command LOAD, the pit commander repeats thecommand and supervises the work of his section. As soonas one or more of the mortars are loaded and laid and alldetails have taken cover, he reports or signals to the batteryexecutive, "Sir, - pit ready." The pit commander alsocommands: LOAD before each salvo of a series. The mortarsare not fired, however, until the command COMMENCE FIRINGis given and the proper firing signal received.

227707°--40-2 5


f. At the command COMMENCE FIRING, if the pieces are un-loaded, the pit commander commands: LOAD and supervisesthe work of his section. The mortars are not fired untilreceipt of the proper firing signal.

g. The pit commander commands: CEASE FIRING whenthe number of shots specified have been fired. He repeatsthe command CEASE FIRING when it is received. At the con-clusion of a series of shots, he reports, "Sir, - pit, (somany) rounds." When dummy ammunition is used, he super-vises unloading of the mortars.

h. In case of a misfire, the pit commander calls, "No. -misfire." He sees that the precautions prescribed in para-graph 42 are observed.

i. At the command REPLACE EQUIPMENT, the pit commandersupervises the replacing of equipment, sees that all mat6rielis properly secured and the emplacement policed, and then,unless otherwise directed, forms his section.

j. The pit commander is responsible to the battery executivefor the observance of all safety precautions at his emplace-ment. When the lanyard is being used, under no circum-stances will he permit a piece to be fired prior to the receiptof both the command COMMENCE FIRING and the proper firingsignal.

* 10. CHIEF OF MORTAR SQUAD.-a. The chief of the mortarsquad (noncommissioned officer) is responsible to the pitcommander for the training and efficiency of his squad andfor the condition and serviceability of the matdriel to whichassigned.

b. At the command DETAILS, POSTS, he takes post where hecan best supervise his squad.

c. At the command EXAMINE GUN, he makes a carefulinspection of the piece and carriage, receives the reports ofthe various details of his squad, and reports to the pit com-mander, "No. - in order," or reports defects he is unableto remedy without delay.

(/. At the command LOAD, he supervises the work of hissquad, gives the commands for and assists in ramming theprojectile. He verifies the laying of the piece in azimuth andif practicable in elevation. If he notes an abnormal changein azimuth differences as indicated by the chalk marks, he

6


notifies the battery executive: if not, he calls or signals,"No. - ready," and takes cover after the other members ofhis squad have reached their cover positions. If his squad isordered to take cover before the piece is laid, he breaks thefiring circuit or, if the firing is by lanyard, requires No. 2 todrop the lanyard. When the mortar is fired, he listens forthe explosion of the primer which may be audible if thepowder charge does not explode. He observes the muzzle ofhis mortar when a salvo is fired and notes whether or notthe piece is discharged. In case of a misfire, he calls out"No. - misfire," and sees that the precautions described inparagraph 42 are taken.

e. At the command RE-LAY, his duties are the same as at thecommand LOAD.

f. At the command CEASE FIRING, when dummy ammunitionis used, he supervises the work of his squad in removing thedummy projectile.

g. He is responsible to the pit commander for the observ-ance of all safety precautions at his piece.

* 11. AZIMUTH SETTER.-The azimuth setter is charged withthe duty of laying the piece in direction. He is responsible tothe chief of the mortar squad for the proper operation, care,and adjustment of the traversing mechanism and for check-ing adjustment of the azimuth index. For detailed duties ofthe azimuth setter, see drill table in section VII.

* 12. ELEVATION SETTER.-The elevation setter is chargedwith the duty of laying the piece in elevation. He is responsi-ble to the chief of the mortar squad for the proper operation,care, and adjustment of the quadrant and elevating mech-anism. For detailed duties of the elevation setter, see drilltable, in section VII.

* 13. CHIEF OF BREECH.-The chief of breech (No. 1) is re-sponsible to the chief of squad for the condition and service-ability of the breech mechanism, breechblock, breech recess,firing mechanism, chamber, and bore. He is also responsiblefor the efficiency of the breech detail and for the observanceof safety precautions insofar as they pertain to his detail.For detailed duties of the chief of breech, see drill table, insection VII.

7


* 14. AZIMUTH RECORDER.-- a. The azimuth recorder is chargedwith the duty of recording all azimuths posted on the displayboard and of checking, marking, and recording each azimuthset on the mortar by the azimuth setter..

b. At the command DETAILS, POSTS, he gets a pencil, chalk,and forms for recording azimuths and takes post near theazimuth setter.

c. At the command TARGET, he records all azimuths postedon the display board. As soon as he hears the azimuth settercall "Set," he checks and records the azimuth setting on themortar and immediately signals or calls, "Azimuth set," in aloud voice, makes a chalk mark on the loading platform op-posite a reference mark on the racer, and takes cover.

d. At the command RE-LAY, he performs the same duties asat the command TARGET.

e. At the command CEASE FIRING, he continues to record theazimuths posted. on the display board. until the commandCEASE TRACKING is received.

* 15. ELEVATION RECORDER.-a. The elevation recorder ischarged with the duty of recording all zones and elevationsposted on the display board and of checking and recording allelevations set on. the mortar by the elevation setter.

b. At the command DETAILS, POSTS, he gets a pencil andforms for recording zones and elevations, and takes post nearthe elevation setter.

c. At the command TARGET, the elevation recorder recordseach zone and elevation posted on the display board. As soonas he hears the elevation setter call "Set," he checks and re-cords the elevation setting on the mortar, signals or calls,"Elevation set," and takes cover.

d. At the command RE-LAY, he performs the same duties asat the command TARGET.

e. At the command CEASE FIRING, hie continues to recordthe elevations and zones posted on the display board untilthe command CEASE TRACKING is received.

* 16. CHIEF OF AMMUNITION.-a. The chief of ammunition(noncommissioned officer) is responsible to the pit com-mander for the efficiency of the personnel of his squad, for thecare and preservation of ammunition and ammunition han-

8


dling apparatus (trolleys, cranes, blocks and chains, shothoists, receiving and delivery tables and trucks), for theobservance of all safety precautions in the care and service ofammunition, and for the police of the magazines and galleriesunder his charge.

b. Before the beginning of an action, he is responsible tothe'pit commander that all shot trucks are loaded and ad-justed and that delivery tables are filled with projectiles.He will see that the service of ammunition is uninterruptedduring the action.

c. At the command DETAILS, POSTS, the chief of ammunitionopens the galleries (and magazines if necessary) and poststhe members of his squad.

d. At the command EXAMINE GUN, the chief of ammunitioninspects the materiel under his charge and gives instructionsfor preparing ammunition and equipment for service or drilland reports to the pit commander, "Ammunition service inorder," or reports defects he is unable to remedy without delay.

e. At the command LOAD, he directs and supervises theservice of ammunition.

f. At the command CEASE FIRING, when dummy ammunitionis used, he causes the dummy projectiles and dummy powdercharges to be put in their proper places in the gallery.

g. At the command REPLACE EQUIPMENT, he supervises thereplacing of equipment, sees that all materiel is properlysecured, forms his squad, and reports to the pit commander.

* 17. AMMUNITION SQUAD.-The ammunition squad, at peacestrength 14 men, at war strength 20 men, is divided intotwo details; the projectile detail and the powder detail. Thesize of the two details depends on local conditions; for ex-ample, the method of ammunition service and the distancethat the ammunition must be moved. The duties of the twodetails may be summarized briefly as follows:

a. Projectile detail.-The projectile detail places the pro-jectiles on the delivery tables and assists in loading themon the shot trucks. One of the cannoneers is designated aschief of detail by the chief of ammunition and the one sodesignated supervises the work of the detail. At times whenthey have no other duties, they clean, paint, and mark

9


projectiles; cleaa, oil, and paint dummy projectiles andshot trucks; clean, oil, and adjust hoists and delivery tables;and police projectile magazines and corridors.

b. Powder detail.-The powder detail removes the chargesfrom the containers; checks and records their weights and allpertinent data, especially lot number; sees that the powderbags are not detective; records temperature of magazines;removes empty containers and places them in a location wherethey will not interfere with the work of the squad; carriesthe powder charges to the emplacement and turns them overto No. 6 of each mortar squad. One of the cannoneers isdesignated by the chief of ammunition as chief of detail andthe one so designated supervises the duties of the detail. Attimes when they have no other duties, they police the powdermagazines; police the portion of the corridors assigned them;and assist the projectile detail, if necessary, in any of itsduties.

U 18. AZIMUTH DISPLAY BOARD OPERATOR.-. The azimuth dis-play board operator is charged with the duty of receivingand posting in legible figures on the azimuth display boardall azimuths received from the plotting room. He repeatsall commands and messages received from the battery com-mander's station and plotting room, making sure that theyare received by the person for whom they are intended.

b. At the command DETAILS, POSTS, he gets chalk and ablackboard eraser and takes post in front of the azimuthdisplay board, facing it.

c. At the command EXAMINE GUN, he cleans his displayboard, puts on his telephone headset, and tests communica-tion to the plotting room (deflection board operator) andbattery commander's station extension. He reports to thepit commander, "Azimuth and BC line in order," or any de-fects he is unable to remedy without delay.

d. At the command TARGET, he repeats in a loud voice theazimuth received from the plotting room and posts it inlegible figures on the display board. As soon as he receivesnew data, he erases the old data and posts the new. Hecontinues this procedure as long as data are being trans-mitted or until the command CEASE TRACKING is received.

10


1 19. ELEVATION DISPLAY BOARD OPERATOR.---a. The elevation

display board operator is charged with the duty of receivingand posting in legible figures on the elevation display boardall zones and elevations received from the plotting room.

b. At the command DETAILS, POSTS, he gets chalk and ablackboard eraser and takes post in front of the elevationdisplay board, facing it.

c. At the command EXAMINE GUN, he cleans his displayboard, puts on his telephone headset, and tests communica-tion to the plotting room (elevation board operator). Hereports to the pit commander, "Elevation line in order," orany defects he is unable to remedy without delay.

d. At the command TARGET, he repeats in a loud voice thezone and elevation received from the plotting room and poststhem in legible figures on the data board. As soon as hereceives new data, he erases the old data and posts the new.Whenever there is a change in zone, he calls, "Change tozone -," and makes certain that the chief of ammunitionis notified. He continues this procedure as long as data arebeing transmitted or until the command CEASE TRACKING isreceived.

* 20. ARTILLERY MECHANICS.-The artillery mechanics, as-

sisted by members of the gun sections, make such minorrepairs and adjustments as can be made with the meansavailable. The chief artillery mechanic is the custodian ofsupplies pertaining to the mortar pits to which his batteryis assigned. He is responsible for the condition of store-rooms pertaining to the mortar pits and the supplies con-tained therein. The chief mechanic or his assistant issuessuch equipment, tools, oils, paints, and cleaning materials tothe members of the gun sections as are necessary for theservice and care of the mortars and accessories.

SECTION IV

NOTES ON THE SERVICE OF THE PIECE

* 21. GENERAL.-a. The drill set forth in this manual is for aM1912 mortar mounted on a M1896MIII carriage. Variationsin the drill for other mortars are-

11


(1) M1890MI.--The operation of the breech mechanism isdifferent. (See par. 24a.)

(2) M1908.--The mortar is brought to the loading positionby means of the quick-loading mechanism without changingthe carriage elevation. This operation is similar to the oper-ation of depressing the other types of mortars.

b. The service of the piece will be conducted with dispatchand precision and with as few orders as possible. Commandswill be given in the prescribed form. Signals may be substi-tuted for commands whenever practicable. Except for thenecessary orders, reports, and instructions, no talking will bepermitted. Cannoneers change positions at a run. Loadingwith dummy ammunition and pointing the piece as for serv-ice firing is the normal practice at drill. Fired service primerswill be used at drill.

c. In manning the rammer, the men take their places inthe following order: The chief of squad at the end, Nos. 1 and5 on the right, and Nos. 2 and 4 on the left, each man grasp-ing the rammer with both hands and as near the outer end ofthe rammer stave as possible, thumbs to the rear. As thetruck comes to a stop at the breech, the projectile is rammedhome instantly and with all possible force, utilizing its mo-mentum, the speed of ramming being accelerated so thatthe maximum is reached as the projectile goes into its seat.Although speed in loading is desired, it must be subordinatedto caution in "running" up the shot truck to the breech recessand in ramming the projectile. Carelessness may result ininjury to the threads of the breech recess, causing the breech-block to stick and slow up the rate of fire. Smooth drill andproperly adjusted shot truck buffers will reduce the possibilityof burring the threads of the breech recess.

* 22. COVER PosTrs.--a. At the command TAKE COVER, given atany time, the squads take position in rear of the emplacement.Each squad is in double column as shown in figure 3.

b. Normally the cover post for No. 4 is the same as his regu-lar post and the squad forms on him at the command TAKECOVER. He does not quit the rammer except at the commandCEASE FIRING, or when directed to do so, in which case he placesthe rammer on the rack or prop.

12


c. When powder is not served from the rear of the pit, thecover post of No. 6 is near the entrance to the gallery fromwhich the powder is served.

d. At the commands, LOAD, RE-LAY, and WITHDRAW POWDERCHARGE, cannoneers having duties to perform proceed to theirposts as quickly as possible without interfering with eachother. Similarly, in taking cover, the details proceed to theirposts as rapidly as possible but should avoid interfering withthose whose duties at the piece have not been completed.

FRONTElevation 7

setterElevation Azimuth setterrecorder

2 112 SHOT 3

8 (or 10) 11 (or9)4 TRUCK 56 Azimuth recorder

FIGURE 3.-COVER POSTS.

* 23. STAND FAST.-If it is desired to halt all movements ofmat6riel and personnel, the officer in charge of the emplace-ment or the pit commander commands: STAND FAST.

* 24. OPERATION OF BREECH.-a. M1890MI mortar.-(1) Toopen breech.-No. 2 pulls out rotating crank lock and turnsrotating crank three times in the direction indicated by arrowmarked "Open." No. 1 then turns translating crank counter-clockwise ending with a quick motion in order to bring thebreechblock to its final position in the tray with a jar sufficientto release tray latch. No. 1 then grasps tray handle, andassisted by No. 2, swings block until tray back latch engagesin its catch.

(2) To close breech.-No. 2 releases tray back latch byraising the handle. He then grasps tray handle and assistedby No. 1 swings tray until it brings up against the face ofthe breech. No. 2 then turns translating crank three timesin a clockwise direction. No. 1 grasps rotating crank handleand turns crank in a clockwise direction until rotating cranklock engages.

13

24-25 COAST ARTILLERY FIELD VIANUAL

b. M1908 and M1912 mortars.-(1) To open breech.-No. 2unlocks breechblock and turns operating crank clockwise untilthe tray comes to rest against the hinge.

(2) To close breech.-No. 2 turns operating crank in acounterclockwise direction until breechblock is translated,rotated, and locked in the closed position.

U 25. SERVICE OF AMMUNITION.--a. When using point deto-nating fuzes, the fuzes must be handled with greatest care.Projectiles are fuzed only as required and in accordance withthe following procedure: The adapter plug is unscrewed fromthe fuze socket and the fuze, fitted with its felt or rubberwasher, is inserted. The fuze is screwed home by hand, thefinal seating being accomplished with the fuse wrench butwithout the use of any great force. If there is any difficultyin screwing the fuze home, the fuze should be removed andanother inserted. If the same trouble is experienced withthe second fuze, the shell should be rejected. Point detonatingfuzes are used for special missions only'.

b. Prior to firing, the primer pouch should be examined tomake certain that it contains live primers only. Fired primersshould be discarded as soon as they are removed from thefiring mechanism. Electric and friction primers should notbe mixed. Electric primers may be distinguished from fric-tion primers by the presence of insulation on the button wire.

c. All members of the gun section should be familiar withthe appearance of equal-section (aliquot) and base and in-crement propelling charges for all zones with particular at-tention to the difference between the igniter end and thefront end of the charge. A misfire or hangfire may occur ifthe propelling charge is loaded with the igniter against theprojectile.

d. When the propelling charge is inserted, it should bepushed into the powder chamber to such a distance that thebreechblock in closing will give the charge a final push intothe chamber.

e. Propelling charges are removed from their containersonly as they are needed; for any given round, the propellingcharge must not be brought out of the gallery until thepreceding round has been fired, the chamber sponged, andthe mushroom head wiped.

14


* 26. LOADING.-At the command LOAD, given by the pit com-mander, the following action is taken by each mortar squad:No. 2 unlocks and opens the breechblock, No. 1 assists himby grasping the body of the block and helping to swing theblock clear. No. 3 holds the block back during the loadingof the projectile and propelling charge. The truck detailruns up the truck; as the truck passes the rammer detail,No. 4 raises the rammer to a horizontal position and placesthe head against the base of the projectile. The chief ofsquad and Nos. 1, 2, 4, and 5 take their places on the rammerand follow the truck. As soon as the truck brings up againstthe face of the breech, the brake is set, the truck detail swingsout and around the truck handles, faces the rear, and holdsthe truck firmly against the breech; crouching down out ofthe way of the rammer detail. As soon as the truck bringsup against the face of the breech, the men on the rammerrun forward and seat the projectile with one motion, usingall possible force. (If the projectile fails to seat, the chiefof squad commands: HOME RAM, and all men working to-gether heave on the rammer until the projectile is pushedhome.) No. 6 places the propelling charge on the truck withthe igniter pad to the rear. No. 2 pushes the charge into thechamber by hand until its face barely clears the gas checkseat so that it will be pushed into the chamber by the mush-room head. No. 2, assisted by No. 1, closes the breech. Assoon as the breech is locked, No. 3 inserts the primer, lowersthe firing leaf, and then commands or signals: ELEVATE.When the mortar is elevated to 430, No. 3 inserts the firingcircuit plug (firing by electricity) or hooks the short lanyardand unhooks the S-hook from the safety lanyard device (firingby lanyard). When firing by lanyard, after the rest of thesquad has taken cover, No. 2 hooks the long lanyard and takespost about 20 feet to the rear of the mortar facing the batteryexecutive and awaiting the command or signal: FIRE.

* 27. POINTING AND FIRING.-a. As soon as the piece is loaded,the azimuth setter traverses the piece to the azimuth postedon the data board, and calls, "Set," to the azimuth recorder.He takes cover only after the azimuth recorder has checkedand recorded the azimuth set and called "Azimuth set" in aloud voice. When No. 3 commands: ELEVATE, the elevation

15


setter assisted by No. 7 unlatches the mortar and elevatesto the approximate elevation expected. When the elevationis posted on the data board, the elevation setter sets his quad-rant, lays the piece for elevation, and clamps it. He then calls,"Set," to the elevation recorder. The elevation setter takescover only after the elevation recorder has checked andrecorded the elevation set and called "Elevation set" in aloud voice. The chief of squad then verifies the laying of thepiece, insertion of the firing circuit plug (firing by electricity),and makes a chalk mark on the loading platform oppositethe reference mark on the racer. If he notes a sudden in-crease in azimuth differences, he notifies the battery executive;otherwise he calls, "No. - ready," and takes cover. Allmembers of the squad take cover posts as soon as their dutiesare completed and in such manner as not to interfere withothers whose duties are not completed.

b. At the command or signal FIRE, NO. 2 pulls the lanyard(firing by lanyard). The chief of squad listens for the explo-sion of the primer which may be heard if the propelling chargedoes not ignite. If a salvo is fired, he watches the muzzle ofhis mortar and notes whether it fires. As soon as the pieceis discharged, the cannoneers take posts at a run. Theelevation setter unclamps the elevating mechanism andassisted by No. '7 depresses the mortar to the loading positionrapidly but without shock, and sees that the spring latch en-gages. When necessary, the azimuth setter traverses themortar to the nearest limit of the loading position. No. 2assisted by No. I opens the breech. No.. 1 wipes off the mush-room head. No. 12 assisted by No. 2 sponges the chamber.When necessary, No. 2 cleans the breech recess and the gascheck seat. No. 3 hangs the short lanyard in the lanyardsafety device, removes the old primer, clears the vent, andcleans the primer seat. All members of the squad standready for the next round.

1 28. DRILL WITH DUMMY AMMuNITIN.--a. For simulatedfire using dummy ammunition, the following procedure isrecommended:

(1) For the first and succeeding odd-numbered rounds, theoperations of loading, pointing, and firing are as given forservice ammunition.

16


(2) For the second and succeeding even-numbered rounds,the operations of sponging and loading are omitted and theoperation of unloading is substituted therefor. As soon asthe projectile is removed, the breech is closed and the opera-tion of pointing and firing proceed as for service ammunition.

b. Unusual events, such as misfires, which may occur dur-ing firing, should be simulated during the drill. They shouldbe called by the executive or pit commander without priorinformation to the mortar squad and in such a manneras to inject realism into the drill.

* 29. POSTING DATA.-Mortar pits are normally equipped witha mechanical system for posting data which is operated fromthe plotting room. This equipment is seldom used. It is con-sidered better practice to have the data transmitted by tele-phone and posted on blackboards by display board operatorswho should be trained to make legible figures. If the me-chanical system is used, its operation should be checkedfrequently.

* 30. BUTTERFLY NET.-The butterfly net mentioned herein isnot an article of issue. One may be readily constructed by avariety of methods. One method is to take a long-handledlanding net or a crab net, replace the netting with burlap,and fasten a heavy hook of small diameter to the handle andwithin the hoop in such fashion that the hook may be usedto unlatch the firing mechanism, the primer dropping intothe net.

* 31. PROTECTION FROM CONCUSSION.--The concussion causedby mortar firing is very strong. Personnel should not standnear walls or over drains when the piece is being fired. Whenpossible, the knees should be flexed and the mouth opened.In general, all doors and windows in the emplacement and inbuildings in the vicinity should be opened. If the plottingroom adjoins the pit, it may be found necessary to close allopenings to prevent the loss of range charts and plottingpaper. The emplacement book should be consulted for infor-mation on damage caused by concussion in previous firingswith a view to preventing its recurrence.

17


* 32. LOADING POSITION LIMITs.-Loading position limitsshould be clearly marked, both on the racer and on the floorof the pit. These markings are necessary on both sides ofany sector of the field of fire in which loading is impossible.The marking should extend far enough back from the mortarto enable the correct positioning of the shot trucks. A methodof marking is to have two parallel lines painted, the distancebetween them being the width of the shot truck. Drill shouldbe conducted at these limiting positions to determine whetheror not there is sufficient clearance for proper ramming.

SECTION V

SAFETY PRECAUTIONS

* 33. GENERAL.--a. The safety precautions given in thissection are prescribed for peacetime conditions. They in-dicate as well the general principles to be followed in warservice conditions.

b. Further instructions concerning safety precautions arefound in AR 750-10 and FM 4-20.

C 34. CEASE FIRING.---a. Any individual in the militaryservice will command or signal CEASE FIRING if he observesany condition which makes it unsafe to fire.

b. At the command CEASE FIRING, given when the pieceis loaded-

(1) If firing by electricity, the executive opens the firingcircuit at the main switch and the chiefs of squad open thecircuit at the mortars by pulling out the firing circuit plug.

(2) If firing by lanyard, the lanyards are detached.

[ 35. FIRING MECHANISM.-a. The firing mechanism will beinspected and tested frequently, and irmmediately before fir-ing to insure proper operation and functioning of the safetyfeatures.

b. To test the: proper functioning of the safety features ofthe mechanism, a friction primer will be inserted before thebreechblock is rotated. A strong pull will be exerted on thelanyard while the block is rotated to ascertain if it is possibleto fire the primer before the breechblock is locked. Themechanism will also be tested in a similar manner with an

18


electric primer, the magneto being operated continuouslywhile the breechblock is being rotated.

c. Previous to firing, all primers to be used will be insertedin the primer seat and the firing leaf and slide will be loweredto their firing positions in order to verify the proper func-tioning of these parts with each primer.

d. A firing mechanism which has been tried and is knownto function satisfactorily in a particular mortar will bestamped with the serial number of that mortar and will beused with that mortar in order to insure proper functioning.

* 36. LANYARD.-The lanyard will not be attached to the firingmechanism until the mortar has been elevated to 43 ° andwill be detached before the mortar (loaded) is depressedbelow 43°. If the mortar is loaded and if a butterfly netis available, it is advisable to remove the primer by meansof the net before the lanyard is detached. Lanyards will bepulled with a quick, strong pull (not a jerk) from a positiondirectly in rear of the piece.

N 37. PRIMERS.-The following precautions will be taken inthe care and handling of primers:

a. Prior to firing, the primer pouch will be examined tomake certain that it contains live primers only.

b. Care will be taken not to drop primers.c. Except when used in testing safety features, primers

will not be inserted until after the breechblock has beenclosed and locked in its recess.

d. Primers will not be inserted or removed by means of thebutton or wire.

e. The greatest care will be exercised in lowering the leaf ofthe firing mechanism.

I. Fired primers will be discarded as soon as they are re-moved from the firing mechanism.

g. Necessary precautions will be taken to prevent any at-tempt to use a primer that has failed.

h. Any primer removed after an attempt to fire will behandled with great care due to the possibility of a primerhangfire.

i. After the primer has been inserted, the slide is lowereduntil the catch engages in the notch of the housing. Pre-

19


caution should tie exercised to insure that the slide is entirelydown before attempting to fire the piece; otherwise theprimer may be blown to the rear, endangering the membersof the mortar squad.

* 38. FUZEs.-Projectiles equipped with base detonating fuzesare received properly fuzed for firing. Projectiles equippedwith point detonating fuzes are received unfuzed and will befuzed as required. (See par. 25a.)

* 39. SERVICE OF POWDER CHARGES.-In the magazine, allpowder charges will be kept in their containers except thecharge which is to be served to the piece for the next suc-ceeding round. The powder charge for any given round willnot be passed out of the gallery until the preceding roundhas been fired, the powder chamber sponged, and the face ofthe mushroom head wiped.

A 40. SPONGING POWDER CHAMBER.-The powder chamber willbe sponged and the face of the mushroom head wiped aftereach shot with the liquid provided for the purpose. (Seepar. 44.)

* 41. COVER FOR GUN SECTION.-When firing high-explosiveammunition and cover is prescribed, each member of the gunsection will be required to take adequate shelter each timethe piece is fired. (See AR 750-10.)

* 42. MISFIRES.-A misfire occurs if the piece fails to firewhen desired. Failure of the piece to fire is due to one oftwo causes; failure of the primer to fire or failure of the pro-pelling charge to ignite. In case of a misfire, all persons willremain clear of the path of recoil, the piece will be kepttrained on the target or on a safe place in the field of fire,and under no circumstances will the mortar be depressedunder 43o .

a. Primer heard to fire.-If the primer is heard to fire itwill not be removed nor the breechblock opened until 10minutes have elapsed after the firing of the primer.

b. Primer not heard to fire.-If the primer is not heardto fire, at least three attempts will be! made to fire it. If a

20


butterfly net is available, the primer may be removed andexamined 2 minutes after the last attempt to fire. If theprimer has not fired a new one may be inserted and firingcontinued. If the primer has fired, a new primer will not beinserted nor the breechblock opened until at least 10 minuteshave elapsed from the last attempt to fire. If a butterfly netis not available, the primer will not be removed nor thebreechblock opened until 10 minutes have elapsed from thelast attempt to fire. (See FM 4-20.)

* 43. EQUALIZING PIPE.-On all mortar carriages, the lowerends of the hydraulic recoil cylinders are connected by anequalizing pipe. Three bronze plugs one of which is a spareare provided to be used in case the equalizing pipe is injuredin action, in which case the equalizing pipe can be entirely re-moved, the plugs screwed into the equalizing pipe seats in thecylinders, the recoil cylinders refilled, and firing continued.

SECTION VI

CARE AND ADJUSTMENT OF MATERIEL

* 44. SPONGING SOLUTION.-. The sponging solution is asolution of water and castile soap. Its purpose is to providea sponging liquid which will extinguish burning residue inthe chamber of the gun and also serve to lubricate thebreech recess. If the soap solution is not available, plainwater may be used.

b. Preparation of the solution consists of dissolving 1pound of castile soap in 4 gallons of water. Yellow soapsshould not be used as they are likely to leave a gummy de-posit in the breech recess. The soap should'be shaved fromthe bar to facilitate dissolving. It is then added to thewater and the water heated until the soap is dissolved. Thewater should be stirred with as little agitation as possibleto prevent foaming.

c. To avoid the necessity of handling large receptacles, asmuch soap as is required for the water to be used can bedissolved in one bucket of water. This concentrated soapsolution can then be added to water in other receptacles inthe prescribed proportions.

21


* 45. CARE OF BORE.-a. As soon as possible after anyperiod of firing, the bore of the mortar will be cleaned toremove all powder residue and then thoroughly oiled. Thecleaning solution is made by dissolving 1/2 to 1 pound (de-pending on the strength desired) of soda ash in each gallonof boiling water. Wash the bore with this solution, using abore sponge around which burlap has been wrapped. Thenusing a sponge wrapped with dry burlap, wipe the borethoroughly dry. Coat the bore with medium or heavy rust-preventive compound, depending on local conditions. Dailycleanings for a period of one or two weeks are usuallynecessary.

b. Care must be exercised to prevent staves of the sponges,slush and cleaning brushes from rubbing against the lowerportion of the bore, as excessive wear of the lands will re-sult from such practice.

* 46. CARE OF CARRIAGE AND BREECHBLOCK.--a. All bearingparts should be thoroughly cleaned and lubricated. Specialattention should be given to the lubrication of the breech-block, trunnion bearings, crossheads and guides, rollers,pintle bearings, and elevating and traversing mechanism,including the teeth of all gears.

b. The carriage should be exercised frequently to insurethat moving parts do not bind and that the whole mech-anism is in proper working order. For this reason, thecarriage should be traversed occasionally 90 ° to the rightand to the left of its normal position when "in service."During this maneuvering, see that the parts of the tra-versing mechanism work freely and that there is no bindingof the pintle surfaces.

c. The mortar should occasionally be elevated to its max-imum elevation and returned to the loading position to insurethat the trunnions and elevating mechanism do not bind andthat these parts work freely.

d. Recoil cylinders should be kept filled.e. Drip pans are provided for the lower ends of the recoil

cylinders. These should be emptied and cleaned occasionally.f. If rust should accumulate, its removal from all bearing

parts, especially piston rods, requires particular attention inorder that clearances shall not be unduly increased. Abra-

22


sives will be used as prescribed in *TM 9-850. Rust may besoftened by using dry-cleaning solvent.

g. Recoil cylinders should be emptied at least every 6months, thoroughly cleaned after each firing, and at leastonce each year regardless of whether the mortar has beenfired or not.

h. Oil holes must be cleaned out frequently to keep themfree from sand, grit, and dirt. They must be kept closed withthe screw plugs or countersunk screws provided. Before oil-ing, wipe off carefully all dirt or grit near the opening thatmight be carried down into the bearing. All oil plugs, screws,covers, and grease cups should be painted red in order thatthey may be readily located. Fittings which cannot be paintedshould have a red ring painted around them.

* 47. FILLING RECOIL CYLINDERS.-a. Carriages M1896MI,MII, and MIII.-To fill the cylinders with oil, remove fillingplugs from both cylinders. Pour clean, light recoil oil into thehole of one cylinder until it flows out the hole of the other.Allow any air that may be present to escape. Then pour inmore oil until it is level with the filling holes. A little morethan 10'/2 gallons is required to fill the cylinders. Oil whichhas been withdrawn from the cylinders or which has beenused for any purpose must never be put in the cylinders againwithout being filtered or carefully strained.

b. Carriage M1908.-Filling holes are provided at about themiddle of each cylinder. The operation of filling should bedone with the mortar horizontal and with both plugs out. Itmay be necessary to elevate the mortar slightly in order toremove or replace the filling hole plugs. Other details of fill-ing and care are the same as those for the M1896MIII car-riage (a above).

* 48. ASSEMBLING AND ADJUSTING OBTURATOR.--. With thebreechblock in the loading position (open), the spindle, withsplit rings (front, rear, and small), gas check pad, and filling-in disk upon it, is inserted into the block. Special care mustbe taken that the front and rear split rings are not inter-changed. Assemble the four obturator spindle washers (two

*See Appendix.

23


bronze and two steel) upon the rear end of the spindle pro-jecting through the block, with a bronze washer in front andthe others alternating steel and bronze. The spindle is thensecured by screwing up the obturator nut by hand. Thebreechblock is then translated and rotated half-way into thefiring position. The split nut is then screwed up as tightlyas possible with the wrenches provided for that purpose andlocked in place by the clamping screw. The spindle is prop-erly adjusted if, while it has no play longitudinally, it canbe turned around freely by taking hold of the mushroom headwith both hands.

b. If, after firing a few rounds, the spindle is found tohave longitudinal play, the adjusting operation describedabove is repeated.

c. The proper adjustment of the obturator is of greatimportance. It should not be made with the breechblockopen, due to the possibility of forcing the gas check padout beyond the split rings and resulting in injury to thepad by pressing it backward over the rear split ring whenthe block is seated.

d. The obturator nut should never be removed while thebreechblock is locked.

e. On the M1908 and M1912 mortars, the four obturatorspindle washers are replaced by an obturator spindle spring.There is no change in assembly or adjustment.

* 49. FIRING MECHANISM.-a. Care.-While this mechanismforms part of a heavy gun, the parts are very closely adjustedand the clearances very small. The greatest care must beexercised, therefore, in keeping the mechanism well oiledand free from rust and dirt. It should not be left on thegun when not in use, but should be kept in the small boxprovided for it and stored in the armament chest.

b. To assemble on gun.-(1) Clasp the hinged collar overthe end of the spindle with the two ribs of the collar engag-ing in the corresponding grooves of the spindle, keeping thehinge at the top.

(2) Take the mechanism in the right hand, holding thecollar with the left, and put the mechanism over the endof the collar. Screw the collar to the left until the catchon the under side of the mechanism engages and locks in

24


position. While doing this, see that the guide bar whichprojects from the right side of the mechanism enters thegroove cut in the breechblock for it, and that the pin onthe safety bar slide (which is attached to the gun) entersthe hole in the outer end of the safety bar of the mechanism.Do not attempt to use the mechanism until it is absolutelycertain that the collar has been screwed entirely home andlocked.

c. To disassemble.-(1) To remove the mechanism fromthe spindle, draw the collar catch to the rear and unscrewthe hinged collar.

(2) To remove the slide from the housing, draw the slidestop out to the left as far as it will go. The slide may thenbe lifted from the housing.

(3) To remove the firing leaf and slide catch from theslide, start the split pin which passes through the leaf pivotby pressing upon it and then draw it out. The pivot is thenfree to be removed, and its removal frees the leaf and slidecatch from the slide.

(4) The collar catch may be removed by unscrewing thescrew at the lower edge of the housing.

(5) The slide stop may be removed by unscrewing it fromthe housing with the wrench provided for that purpose.The slide stop should not be removed except when necessaryto repair it or to replace a broken spring.

(6) The contact clip may be removed from the leaf byunscrewing the nut on the underside of the leaf.

* 50. To TEST LANYARD SAFETY DEVICE.-With the mortarin the loading position, place the bridle ring (S-hook) in thebridle ring catch. Keeping a strong pull on the lanyard as ifattempting to fire the piece, elevate the mortar slowly to43 ° elevation. The ring should pull free between 41°45' and43 ° . The drill in this manual prescribes that the lanyard willnot be attached to the firing mechanism until the mortar iselevated to 43° .

* 51. TO TEST ELEVATION FRICTION DEVICE.-The elevationfriction device should be tested before and after firing in orderthat proper adjustment may be made. It is properly adjustedwhen, with the mortar depressed against the stop, the com-

25


bined efforts of two men, one at each handwheel, are justsufficient to cause slipping of the friction device when anattempt is made to depress the mortar. This test is thesame for all mortar carriages with the exception that, onthe M1908 carriage, the maximum effort of one man shouldbe sufficient to slip the device.

1 52. TECHNICAL INFORMATION ON MORTAR CARRIAGES.-While

pertaining specifically to the mortar carriage M1896MIIIfor the M1912 mortar, *TM 9-420 contains a great deal ofinformation on the care and adjustment of mat6riel that alsoapplies to the other mortar carriages.. For this reason, andalso because it is the only technical manual published onmortar carriages, it should be obtained by all batteries man-ning mortars and distributed to include all interested non-commissioned officers.

*See Appendix.

26

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T-1EfeH--MeRw*a- IFIXED -ARaMAEN a

APPENDIX

LIST OF REFERENCES

Ammunition, general ____________ TM 9-905 (now publishedas TR 1370-A).

Camouflage, cover, p r o t e c t i o nagainst air and chemical attacks,local security, machine-gun de-fense_ __-_-_____-_-_-____E-- - FM 4-5.

TM 9-850 (now publishedCare and maintenance of materiel_ as TR 1395-A).

FM 4-20.Coast Artillery ammunition_______ TM 4-205.Coast Artillery weapons and ma-

teriel-_________________________ TM 4-210.Commands ---- _________________ FM 4-5.Drill ammunition -----__ _________ TM 9-905 (now published

as TR 1370-D).Examination of gunners__________ FM 4-150.Fire control and position finding___ FM 4-15.Firing tables:

Deck piercing, equal section(aliquot) propelling charge_ 12-A-4.

Deck piercing, base and in-crement propelling charge__ 12-G-1.

700 lb. HE shell Mk VI and VIa,base and increment pro-pelling charge_____________ 12-I-1.

Gunnery _______________________ FM 4-10.(Ord. Docs. 1705 and 1820.

Mortar mat6riel, including mortar, TM 9-420 (now publishedcarriage, and firing mechanism_ as TR 1315-12M).

Organization of the battery F M----_- . 4-567.

Safety precautions in firing-__-_---AR 750-10.

27 420.

27