A discrepancy between a calculated and tabulated result will serve to show the influence of a slight change in the coefficient of reduction n, and the muzzle velocity V.

Example 3

Determine by calculation with the abridged ballistic table the remaining velocity v, the time of flight t, angle of elevation φ, and descent β of this 6-in. gun at ranges 500, 1000, 1500, 2000 yds., taking the muzzle velocity V = 2150 f/s, and a coefficient of reduction n = 0.96. [For Table see p. 274.]

An important problem is to determine the alteration of elevation for firing up and down a slope. It is found that the alteration of the tangent elevation is almost insensible, but the quadrant elevation requires the addition or subtraction of the angle of sight.

Example

Find the alteration of elevation required at a range of 3000 yds. in the exchange of fire between a ship and a fort 1200 ft. high, a 12-in. gun being employed on each side, firing a shot weighing 850 lb with velocity 2150 f/s. The complete ballistic table, and the method of high angle fire (see below) must be employed.

Range.

s.

s/C.

S(v).

v.

T(v).

t/C.

t.

T(v).

v.

D(v).

φ/C.

φ.

β/C.

β.

0

0

0

20700.53

2150

28.6891

0.0000

0.000

28.6891

2150

50.9219

0.0000

0.000

0.0000

0.000

500

1500

518

20182.53

1999

28.4399

0.2492

0.720

28.5645

2071

50.8132

0.1087

0.315

0.1135

0.328

1000

3000

1036

19664.53

1862

28.1711

0.5180

1.497

28.4301

1994

50.6913

0.2306

0.666

0.2486

0.718

1500

4500

1554

19146.53

1732

27.8815

0.8076

2.330

28.2853

1918

50.5542

0.3677

1.062

0.4085

1.181

2000

6000

2072

18628.53

1610

27.5728

1.1163

3.225

28.1310

1843

50.4029

0.5190

1.500

0.5989

1.734

Range Table For 6-inch Gun.

Charge

{

weight, 13 lb 4 oz.

Projectile

{

Palliser shot, Shrapnel shell.

Muzzle velocity, 2154 f/s.

gravimetric density, 55.01/0.504.

Weight, 100lb.

Nature of mounting, pedestal.

nature, cordite, size 30

Jump, nil.

Remaining Velocity.

To strike
an object
10 ft.
high
range
must be
known to

Slope of Descent.

5′ elevation or
depression alters
point of impact.

Elevation.

Range.

Fuse
scale for
T. and P.
middle
No. 54
Marks I.,
II., or III.

50% of rounds
should fall in:

Time of Flight.

Penetration
into
Wrought
Iron.

Range.

Laterally
or
Vertically

Length.

Breadth.

Height.

f/s.

yds.

1 in

yds.

yds.

° ′

yds.

yds

yds

yds

secs.

in.

2154

..

..

..

0.00

0 0

0

..

..

..

..

0.00

13.6

2122

1145

687

125

0.14

0 4

100

¼

..

0.4

..

0.16

13.4

2091

635

381

125

0.29

0 9

200

¾

..

0.4

..

0.31

13.2

2061

408

245

125

0.43

0 13

300

1

..

0.4

..

0.47

13.0

2032

316

190

125

0.58

0 17

400

1¼

..

0.4

..

0.62

12.8

2003

260

156

125

0.72

0 21

500

1¾

..

0.5

0.2

0.78

12.6

1974

211

127

125

0.87

0 26

600

2

..

0.5

0.2

0.95

12.4

1946

183

110

125

1.01

0 30

700

2¼

..

0.5

0.2

1.11

12.2

1909

163

98

125

1.16

0 34

800

2¾

..

0.5

0.2

1.28

12.0

1883

143

85

125

1.31

0 39

900

3

..

0.6

0.3

1.44

11.8

1857

130

78

125

1.45

0 43

1000

3¼

..

0.6

0.3

1.61

11.6

1830

118

71

125

1.60

0 47

1100

3¾

..

0.6

0.3

1.78

11.4

1803

110

66

125

1.74

0 51

1200

4

..

0.6

0.3

1.95

11.2

1776

101

61

125

1.89

0 55

1300

4½

..

0.7

0.4

2.12

11.0

1749

93

56

125

2.03

0 59

1400

4¾

..

0.7

0.4

2.30

10.8

1722

86

52

125

2.18

1 3

1500

5

..

0.7

0.4

2.47

10.6

1695

80

48

125

2.32

1 7

1600

5½

25

0.8

0.5

2.65

10.5

1669

71

43

125

2.47

1 11

1700

5¾

25

0.9

0.5

2.84

10.3

1642

67

40

100

2.61

1 16

1800

6¼

25

1.0

0.5

3.03

10.1

1616

61

37

100

2.76

1 22

1900

6½

25

1.1

0.6

3.23

9.9

1591

57

34

100

2.91

1 27

2000

7

25

1.2

0.6

3.41

9.7

The last column in the Range Table giving the inches of penetration into wrought iron is calculated from the remaining velocity by an empirical formula, as explained in the article ARMOUR PLATES.