MIL-C-46409D (AR)
APPENDIX "E" (CONT'D)
30.3.1.4 Mean Radius (M.R.) The arithmetic mean of the distances between the center of
all shot-holes and a point of the target called the Center of Impact.
30.3.1.5 Extreme Vertical (Ex. Ver.). Vertical distance between the center of the hole made
by the uppermost shot and the center of the hole made by the lowermost shot.
30.3.1.6 Extreme Horizontal (Ex. Hor.) Horizontal distance between the center of the hole
made by the shot farthest to the right and the center of the hole made by the shot farthest to the
right and the center of the hole made by the shot farthest to the left.
30.3.1.7 Extreme Spread (Ex. Spr.). Distance between centers of the shot-holes farthest
apart.
30.3.1.8 Center of Impact (C.I.). Defined as the point at which the algebraic sum of the
components; of the distances to the center of each shot-hole is zero.
30.3.2 The procedure for obtaining the Diagonal (D) for each target shall be as follows:
30.3.2.1 One each target, draw a rectangle whose four sides pass through the centers of the
out most holes (See Figure E-3). The top and bottom lines of the rectangle shall be horizontal;
the vertical lines shall be perpendicular to the horizontal lines.
30.3.2.2 The Diagonal (D) of each rectangle shall then be measured to the nearest tenth of
an inch. The Diagonal may be measured from the upper left comer to the lower right corner, or
from the upper right comer to the lower left comer.
30.3.2.3 The Mean Diagonal (M.D.) shall be obtained by adding the individual diagonal
measurements and dividing by the number of targets.
30.3.3 Mean Radius for targets shall be determined in the manner indicated below, and
illustrated in Figures E-1 and E-2.
30.3.3.1 Draw a horizontal line, PA, through the center of the lowest shot-hole on the target
and extend it horizontally in both directions until its length is equal to or greater than the width of
the group of shots comprising the target.
30.3.32 Draw a vertical line, PB, through the center of the shot-hole on the extreme left of
the target perpendicular to and meeting line PA at P. Extend line PB above PA unil the length of
PB is equal to or greater than the height of the group of shots comprising the target.
30.3.3.3 Measure (by means of the scale or opisometer) the perpendicular distance Y from
the center of each shot-hole on the target to line PA. Add the distances so obtained d divide by
the number of shots. The results of this calculation is the average vertical distance of the shot-
holes above the base line PA and is designated by Y. Similarly, measure the perpendicular
distance X from the center of each shot-hole to line PB, add the distances so obtained and divide
by the number of shots. The results is the average horizontal distance of the shot-holes from the
vertical ordinate PB, and is designate X.
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