Coast Artillery Gunnery (1940)

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    MHI FM 4-10C-;- v 3WAR DEPARTMENT

    COAST ARTILLERYFIELD MANUALSEACOAST ARTILLERY

    GUNNERY

    I A

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    COAST ARTILLERY FIELD MANUALdestroyer at a range of 6,000 yards from the gun. The tideis * * * to be found. What is the corrected range?

    * *. * * * * *

    [A. G. 062.11 (2-7-42).] (C 1, April 24, 1942.)* 43. GENERAL.

    * * * * * * *

    b. After the uncorrected range and azimuth have been deter-mined, the preparation of firing data is completed by applyingcorrections to these data for all known nonstandard conditions.Uncorrected range is used for computing range correctionsand corrected range is used for computing azimuth correc-tions. [A. G. 062.11 (2-7-42).] (C 1, April 24, 1942.)* 45. ACCURACY OF COMPUTATIONS.

    * * * * * * *Solve to oruse nearest-

    Firing range__--_____-------.-----_-------. 10 yards.Firing elevation__________________-_------. 1 mil or minute.Firihg azimuth or deflection ----_-__-------- 0.010 or 1 mil.Range for determining differential effects_ ..-100 yards.Range effects, distances in all calculations___.. 1 yard.Lateral effects _______------_--_--_-------- 0.01 or 1 mil.Latitude of gun --------------------------. 1 .Azimuth of target (rotation or wind) -_______ or 1 mil.Height of site --- __--------------------- _ I foot.

    * * * * * * *

    [A. G. 062.11 (2-7-42).] (C 1, April 24, 1942.)* 47. DEFINITIONS.

    * * * * * * *

    c. Dead areas.-Areas that cannot be reached by fire. Thesemay be caused by masks in front of the battery as well as byobstructions in the descending path of the projectile and alsoby height of site of the gun.

    [A. G. 062.11 (2-7-42).] (C 1, April 24, 1942.)* 52. GENERAL.-Frequently it is * * * listed in table A ofthe firing tables. If more accuracy is needed, the problem maybe solved by computation from the firing tables, using themethod given in paragraph 26b.

    [A. G. 062.11 (2-7-42).] (C 1, April 24, 1942.)2

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    COAST ARTILLERY FIELD MANUAL* 72. COMPUTATION OF CHECK POINTS, COORDINATES KNOWN.

    NOTE.-Ay should be corrected for magnification of scale when risingstandard grid coordinates. (See table XLIX, TM 5-236.)[A. o. 062.11 (2-7-42).] (C 1, April 24, 1942.)* 74. EXAMPLES.-a. Given the following data (standard gridcoordinates):

    * * * * * * *Latitude and longitude of directing point G, 37 N. and

    7618 ' W., respectively. Correction' to Ay for magnification ofscale error=1.06 yards per thousand yards. (See TM 5-236.)

    * * * * * * *[A. G. 062.11 (2-7-42).] (C 1, April 24, 1942.)* 89. CORRECTIVE MEASURES.-Fixed seacoast guns * * * ifrequired, vertical angles. If a deflection is set on the sightand the gun traversed until the line of sight includes thetarget, the axis of the trunnions is given a definite direction.Since the axis of the bore * * * "compensating sightmounts."

    [A. G. 062.11 (2-7-42).] (C 1, April 24, 1942.)* 102. DEVIATIONS.

    b. The center of im2pctt, or mean point of impact, of a seriesof shots is a point whose position is fixed by the positions ofthe several points of impact. The range deviation of the centerof impact is the algebraic mean of the range deviations ofthe separate impacts.* 119. EXAMPLES.

    d. * * *For tactical No. 4, register No. 47:

    (3X8X(+8))+(8X(+16))+(8X(+10))+(10X(+14))+(8X(+10)) +620(3XS)+8+8+10+8 58+11/*[A.G. 062.11 (2-7-42).] (C 1, April 24, 1942.)

    * 128. COMPUTATION OF PROBABILITY IN OTHER OPERATIONS.-The method of calculating the probability of a shot's fallingbetween certain points given in paragraph 127 is equally ap-plicable to the calculation of the probability that any variable

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    GUNNERYdistributed in the same manner will take on a value betweenspecified limits. It has been mentioned in paragraph 107 thataccidental errors are usually considered as distributed in thisway. In fact, the study of the distribution of accidentalerrors * * * calibration, and pointing.

    [A. G. 062.11 (2-7-42).] (C 1, April 24, 1942.)* 130. COMPOUND ERRORS.

    * * * * * * *

    b. The spotting error is not independent of the magnitudeof the deviation (the larger the deviation the less accuratethe spot), so that in compounding it with other errors thesecond of the conditions listed in the rule above is not fulfilled.It is permissible to assume * * error of observation.

    [A. G. 062.11 (2-7-42).] (C 1, April 24, 1942.)* 134. BASIC PRINCIPLES.- * * *

    * * * * * * *

    j. Having decided that a correction is necessary, it shouldbe made to the nearest lo of 1 percent of the range or nearest10 yards.

    * * * * * * *

    r. Occasionally an erratic or wild shot will be fired. A shotshould be considered wild when its impact is more than fourdeveloped armament probable errors or, in the absence of thisinformation, more than six firing table probable errors fromthe center of impact. A wild shot should be disregarded indetermining an adjustment correction. Obviously, a wild shotcannot be identified until sufficient rounds have been firedto give a reasonably accurate location of the center of impact.

    * * * * * * *

    [A. G. 062.11 (2-7-42).] (C 1, April 24, 1942.)* 139. MAGNITUDE METHOD (DEVIATIONS MEASURED).--In thismethod of adjustment of fire, the magnitude and sense of therange deviation (in terms of its corresponding correction)of each shot or salvo center of impact are spotted and theimpacts are plotted graphically on the fire adjustment board.(See FM 4-15.) Corrections, mathematically as correct * *slow rate of fire.

    [A. G. 062.11 (2-7-42).] (C 1, April 24, 1942.)* 142. ADJUSTMENT FOR DIRECTION.

    * * * * * * *5

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    COAST ARTILLERY FIELD MANUALc. When employing case II fire, lateral corrections may be

    made by an axial observer located near the guns who calls thecorrection deflection.[A. G. 062.11 (2-7-42).] (C 1, April 24, 1942.)* 143. GENERAL.-In this method, the magnitude and the senseof the range deviation (in terms of its corresponding correc-tion) of the center of impact of a series of shots or salvosare the basis for determining the range correction to be applied.On the fire adjustment board * * * on the same correction.

    [A. G. 062.11 (2-7-42).] (C 1, April 24, 1942.) 146. EXAMPLES.-a. The following examples of range adjust-ment are based on the use of the fire adjustment board (seeFM 4-15). The standard system of reference numbers is usedin which 300 represents a zero correction, and the digit inthe units' place represents tenths of 1 percent. For example,315 represents a correction of up 1.5 percent. The data forthe examples were determined by means of the dispersion tapeand scale described in appendix I. A probable error of 1 per-cent is assumed for convenience in all examples.

    b. In the examples, certain conventions have been followedas indicated below:(1) A cross (X) is used to denote a single shot. (A cross

    with an exponent would be used to denote the center of im-pact of a salvo, the exponent being the number of shots inthe salvo.)

    * * * *. * * *

    (3) A check mark is used to show two things, the first beingthe location of the center of impact of the shots consideredas a basis for a correction, and the second being the magnitudeof the adjustment correction.

    (4) The numbers immediately above a check mark indicate,in reference numbers. the correction ordered.

    (6) The vertical scale is uniform. A different horizontal lineis used for each salvo both in trial fire and fire for effect.When conducting trial fire by single shots, if a correction

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    GUNNERY

    is applied after the first shot, then the second shot isplotted alone on the next line and the succeeding shots oftrial fire are plotted two to a line. During fire for effect,the shots are plotted two to a line. The board presents atall times a chronological record of the fire adjustment.

    * * * * * * *c. For the examples in this section, the assumed situation

    is as follows: * * * * * *

    Example No. 1.-Tabulated data.Uincor- Adjustment'Uncor- Adjustment Point of impact Corectedrected range correction Pointofimpat ConoctedShot No. plus ballis-_ rangetic corree- (yards)tion (yards) Percent Yards Percent Yards

    T. S. 1 12, 050 300 0 258 +510 12, 050T. S. 2---- - 12, 010 258 -500 320 -240 11,510T. S. 3-------- 11,970 258 -500 315 -180 11, 470T. S. 4-------- 11,930 258 -500 304 -50 11,430S--1 ------ - 11, 640 268 -370 320 -230 11, 270

    11, 640 268 -370 290 +120 11,270S-2 ------- - 11,530 268 -370 318 -210 11, 160

    11, 530 268 -370 314 -160 11, 160S-3 --------------- 11,420 268 -370 297 +30 11,050

    11,420 268 -370 325 -290 11,050S-4 ------ - 11,300 273 -310 300 0 10, 990

    11,300 273 -310 308 -90 10, 990S-5 ------- - 11,180 273 -300 302 -20 10, 880

    11, 180 273 -300 294 +70 10, 880S-6 ------- - 11,060 278 -240 307 -80 10, 820

    11, 060 278 -240 291 +100 10, 820S-7 ------- - 10, 940 278 -240 301 -10 10, 700

    10, 940 278 -240 295 +50 10, 700

    In example No. 1 (fig. 36), the first ranging shot wasreported as 258 or over 510 yards. Since this shot wasmore than three probable errors from the target, a correctionof 258 was ordered to bring the remaining trial shots closerto the target. The deviations of all four trial shots wereconsidered * * * from the line of targets, and no correctionwas applied.

    [A. G. 062.11 (2-7-42).] (C 1, April 24, 1942.)

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