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  • 8/8/2019 Field Artillery Notes 7




    Field Artillery NotesNo. 7



  • 8/8/2019 Field Artillery Notes 7




    C L A S S N U M B E R HL $ ' 9

    ACCE SSION NUM BER - tL 'r / ii


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    The following pamphlet "Field Artillery Notes No. 7," ispublished for the information of all concerned.

    i;300.8 A. G. O.]; B Y ORDER OF THE SECRETARY OF WAT; :

    II . L. SCOTT,Major General, Chief of Staff.

    O F F I C I A L :H . p . M C C A I N ,

    The Adjutant General.3

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    Washington, June 19,1917.To all officers of the Army:

    You are advised that this and all subsequent documents of asimilar character, which may be furnished to you from thisoffice, are to be rega rded a s strictl y confidential. They a re tobe kept at all times in your personal possession and are not to becopied nor are any parts of their contents to be communicated,either directly or indirectly, to the press nor to any persons notin the military or naval service of the United States. In Eu ropethese documents are not to be carried into the front-line trenchesnor farther to the front than the usual post of the officers towhom issued.

    Strict compliance with this injunction is enjoined upon everyofficer into whose hands any of these confidential documentsmay come.

    By order of the Secretary of War:H. P. MCCAIN,

    The Adjutant General.(4)

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    Rang ing on the line of observation 7

    Notes for Artillery officers on shoots with aeroplane observa-

    Notes on cooperation between aircraft and Artillery during

    Definition of terms used in the registration of zones and intren ch warfare by Field Artillery 4.1

    Notes on meteorological telegrams to the Artillery 15

    tion 21Notes on wireless 22

    recen t operations on th e second Arm y front 24Stokes' tren ch howitzer 3-inch mark 1 29

    Sup ply of amm unition in the field 42G. H. Q. Artillery circular No. 5:

    Field Artillery 45

    Notes on employment of serviceable guns.and trench mortars

    The employment and duties of the Artillery nights in trench

    Ex trac t from a recen t report from an officer serving in western

    Techn ical notes on 18-pounder barrages 45Small caliber gun s; German Arm y 50

    captured from the enemy 52Tren ch mortars 54The grid plotter 83

    warfare 85App lication of meteorological data in gun nery 92

    Europe 945

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    I.Employment oftrench mortars Page.1. (" of th e different nat ure s 542. Organization and command 543. Use in attack 554. Use in defense . 58

    II.Selection, preparation, andoccupation of positions5. Selection of positions 596. Positio ns for offensive operation s 607. Positions for holding the line 618. Battery headqu arters 619. Mortar emp lacemen ts 61

    10. Communications 6211. Am munition supp ly 6212. Maps 63

    III.Gunnery13. Line s of lire 6314. Ranging 6415. Distrib ution of lire 68

    16. Causes affecting accu racy of fire 7017. Registration 7018. Methods of engaging objectives 7119. Gas, smoke, and incendiary bombs 71

    IV. Conclusion20. Conclusion 71

    App endix A.Type of trench mortar position 72B.Types of trench mortar emplacements 73C.Type of tren ch mortar platforms .. 76D. Details of tren ch mortars 78E.D etails of amm unition. 80F.Notes on trench artillery 81

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    GENERAL STAFF, W AR OFFICE,. . : . . . 1 9 1 6 .

    [This supersedes th e pamphlet entitled "A Few Notes on Ranging SiegeHowitzers with Visual Observation," issued November, 1915, allcopies of which should now be destroyed.]

    When observation takes place from a forward observing station, it is obvious that the observing officer will be approximatelyin the line of fire to only a smallportion of the area allotted to hisbattery.

    The farther forward he is thesmaller will be this portion.

    It follows that, with the majority of objectives, his line of visionwill make a considerable angle withthe line of fire from the battery.

    Prom a position such as this, itis in many cases impossible to sayhow shells are falling as regardsthe line of fire; all that, an observercan generally do is to measure theamount the shell falls right or leftof his line of observation, unless theshell falls in line with the target,when he can also say if the roundis plus or minus of the targeton Msline of observation.

    When, therefore, observing froma position to a flank, a round mustfirst be placed on the observer's lineto the target.

    When this has been done; bracketing is carried out in the usual way, 6but on the observer's line to the FIG,, instead of the line batte ry target. This is called " ranging on the line of observation," and tho following is the system.

    It must be borne in mind that a round that can be judged plusfrom O is not necessarily plus from B and vice versa. For instance, in Pig. 1. rounds in the sector XT W are plus from the

    . . . . . . . . 7 .

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    observer and minus from the battery, whereas rounds in thesector Z T Y are minus from the observer and plus from thebatt ery . Also rou nd s observed left from th e observer are notnecessarily minus, and rounds observed right are not necessarilyplus.

    When ranging along the L. of O, it is better to speak of plusand m inus and right and left as referring to O T and not B T .

    The positions of the battery, observation station, and approximate position of the target are markedon the map. Hence the distancesO T and th e angle O T B can beobtained.

    Presuming in Fig. 2, the first shotfalls at S, all the observer can tell istha t it is on the line O X, and so many

    , degrees and minu tes righ t of his line* O T. H e can not judge if the round is\ plus or m in us ; all he can do is to

    1meas ure the amount right. He must

    \ now give a correction to bring thenext shot on to his line.

    He can either decrease his elevation and bring the next shot to Sior give more left deflection and bringit to S2. Wh ich is preferab le willbe discussed later on.

    The problem, then, is to convert thedegrees or minutes which the B.C.has observed the shot fall right orleft of his line to degrees and minutes of gun elevation or gun deflec

    tion. The facto rs:... Minu tes of gun eleva tion _ E'' Minutes of observation R. or L.~~O

    o\ _ M inutes of gun deflection D% ' Minu tes of observation R. or L."O

    g are found either by taking them frompJG 2 the " Table of Angles " or by calcula

    tion. Th e method of calculation is shown on page 7.One of these factors is now applied.

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    Presume ^r=-,c-and VJ=TT and the shot falls 3 right, it in

    brought on to the L. of 0 by giving- X3 = I less elevation, or by-

    giving TT X 3 =3 0 min utes more left deflection.

    EPresuming in Fig. 3 tha t ^ is used. The n ext round should

    therefore fall at S2, and can be observed as line and minus(along the L. of O ). It is now required to bring the shot tothe other side of the target and keep it on the L. of O.

    It is clear that if only elevation is given, the shot will fallat Z, and if only deflection isgiven, it will fall at Y, andthat to bring it to the desiredspot, namely, S3, the elevationmust be increased, and a cor

    responding correction madefor th e deflection. To get thiscorresponding deflection, athird factor, generally calledthe combined factor, namely,minutes of gun deflection*_Dminutes of gun elevation*~Eis used. Presume this is


    Then if the short bracket=20', and the B.C. goes up SO';

    s-X 80= 40, more left is also requ ired. Rang ing is the n p roceededwith un til the targ et is found. When close to the targe t, and it

    is a small one, judgment is required by the B.C. to determinewhether the final small corrections required are those of deflection or elevation. ^

    Theoretically, the above system is perfect, and if a gun had no50 per cent zone the target is bound to be found very quickly.Practically, with small 50 per cent zones, there should be verylittle more difficulty in finding the target than when ranging

    * Required to bring a shot which is or 100 yards on B T on tothe Ii. of O.

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    10 FIELD ARTILLEEY NOTES NO. 7.along the battery line. Big 50 per cent zones, however, causedifficulties to many B.C.'s, especially with a narrow target, andit is found tha t B.C.'s do not sufficiently study the 50 per centzones and the effect caused by them when ranging on the L. of

    O. A big 50 per cent zone will cause shell which are expected tofall on the observer's line to often fall righ t or left of it. B.C.'smake the mistake of correcting on these rounds instead ofrepeating them.

    E. g.: R=8,000, O T=700, O T B=40, 50 per cent zone=45yards, target a group of houses 20 yards square. The targetsubtends about 11 either side of the L. of O. Fifty per cent ofthe rounds will fall right or left of the target, and, unless thereis a favorable wind, will not admit of being observed plus orminus

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