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PRINCIPLES OP GUNNERY. 
Table of Probability Factors. 
Per 
cent. 
Factor 
Per 
cent. 
Factor 
Per 
centi 
Factor 
Per 
cent. 
Factor 
Per 
cent. 
Factor 
1 
•02 
21 
•40 
41 
•80 
61 
1-27 
81 
1-94 
2 
•04 
22 
•41 
42 
•82 
62 
1-30 
82 
1-98 
3 
•06 
23 
•43 
43 
•84 
63 
1-33 
83 
2-03 
4 
•07 
24 
•45 
44 
•86 
64 
1-36 
84 
2-08 
5 
•09 
25 
•47 
45 
•89 
65 
1-39 
85 
2-13 
6 
•11 
26 
•49 
46 
•91 
66 
1-42 
86 
2-18 
7 
•13 
27 
•51 
47 
•93 
67 
1-45 
87 
2-24 
8 
•15 
28 
•53 
48 
•95 
68 
1-48 
88 
2-30 
9 
•17 
29 
*55 
49 
•98 
69 
1-51 
89 
2-37 
10 
•18 
30 
•57 
50 
1-00 
70 
1*54 
90 
2-44 
11 
•20 
31 
•59 
51 
1-02 
71 
1-57 
91 
2-52 
12 
•22 
32 
•61 
52 
1-04 
72 
1-60 
92 
2-60 
13 
•24 
33 
•63 
53 
1-07 
73 
1-64 
93 
2-69 
14 
•26 
34 
•65 
54 
1-09 
74 
1-67 
94 
2-78 
15 
•28 
35 
•67 
55 
1-12 
75 
1-71 
95 
2-91 
16 
•30 
36 
•70 
56 
1*14 
76 
1-74 
96 
3-04 
17 
•32 
37 
•72 
57 
1-17 
77 
1-78 
97 
3-22 
18 
•34 
38 
•74 
58 
1-19 
78 
1-82 
98 
3-45 
19 
•36 
39 
•76 
59 
1-22 
79 
1-86 
99 
3-82 
20 
•38 
40 
•78 
60 
1-25 
80 
1-90 
100 
a 
Thepro-Qf Take for example the case of the 40-pr. M.L.E. gun at 5° elevation, 
hitting a The depth of the zone containing 50 per cent, of the shot is 
givfifa? 30*25 yds.; the breadth of the zone containing 50 per cent, of the 
^tensions. shot is 2*08 yds. 
What per-centage of shot from the 40-pr. M.L.E. at 5° elevation 
at a mean range of 2387 yds. will probably hit a horizontal target 
40 yds. long by 4 yds. broad ? 
The probability factor for length is obtained by dividing the length of 
the target by the depth of the zone containing 50 per cent, of the 
shot. Thus, 
40 
probability factor for length = - - ■■ = 1*32. 
o 5 
By reference to the Table of Probability Factors it will be seen that 
1*32 corresponds to 62*7 per cent., which shows that 62*7 per cent, of 
the shot will probably fall into a zone 40 yds. in depth and of indefinite 
breadth. 
The probability factor for breadth is obtained by dividing the breadth 
of the target by the breadth of the zone containing 50 per cent, of the 
shot. Thus, 
4 
probability factor for breadth = = 1*92. 
By reference to the Table of Probability Factors, it will be seen 
that 1*92 corresponds to 80*5 per cent., which shows that 80*5 per cent, 
of the shot will probably fall into a zone 4 yds. in breadth and of 
indefinite length. 
The product of the per-centages thus found will give the per¬ 
centage of hits on the target. Thus, probable number of hits= 62*7 
per cent, of 80*5 per cent. = 50*5 per cent. 
The same method applies for determining the per-centage of hits on 
a vertical target, if the mean vertical and lateral errors of the gun. are 
known, 
