112 
ROTATION OF PROJECTILES, 
Appended is a table which may prove useful. It requires no ex¬ 
planation. The value of a — y is given in each case, as the calculation 
of that factor is the most laborious part of any calculation for the 
value of n. Knowing these values of a — it is very easy to calculate 
n for any special projectile of a kind not given in the table. 
Table calculated from Prof. GreenJdlVs Formula for Stability of Potation of 
Projectiles. 
(R.A.I. “Proceedings,” Vol. X., p. 586.) 
Length of projectile in cals. 
Value of 
a — 7 . 
Minimum twist at muzzle of gun requisite to give stability of 
rotation = 1 turn in n calibres. 
Cast-iron common 
shell: 
Cavity = •^ f ths vol. 
of shell. 
(s.g. of iron = 7*207) 
Palliser shell: 
Cavity = | th vol. 
of shell. 
(s.g. = 8 * 000 .) 
Solid steel bullet. 
(s.g. = 8 * 000 .) 
Solid lead and tin 
bullets of similar 
comp 11 to M.-H. 
bullets. 
(s.g. = 10*9.) 
Value of n. 
Value of n. 
Value of n. 
Value of n. 
2*0 
•49418 
63-87 
71*08 
72*21 
84*29 
2-1 
•52032 
59*84 
66-59 
67*66 
78*98 
2-2 
•54431 
56-31 
62-67 
63*67 
74-32 
2-3 
•56643 
53*19 
59-19 
60*14 
70-20 
2-4 
•58679 
50-41 
66-10 
57-00 
66-53 
2*5 
•60561 
47-91 
53-32 
54-17 
63-24 
2-6 
•62315 
45*65 
50-81 
61-62 
60-26 
2-7 
•63938 
43-61 
48-53 
49-30 
57-55 
2-8 
•65454 
41-74 
46-45 
47-19 
55-09 
2*9 
•66868 
40-02 
44*54 
45*25 
52*72 
3-0 
•68192 
38-45 
42*79 
43*47 
50-74 
3-1 
•69434 
36*99 
41-16 
41-82 
48*82 
3-2 
•70598 
35*64 
39*66 
40*30 
47-04 
3-3 
•71693 
34-39 
38*27 
38*84 
45-38 
3*4 
•72724 
33-22 
36*97 
37*56 
43*84 
3-5 
•73697 
32-13 
35-75 
36*33 
42*40 
3-6 
•74615 
31-11 
34-62 
35*17 
41*05 
3-7 
•75483 
30*15 
33-55 
34*09 
39*79 
3-8 
•76303 
29-25 
32-55 
33*07 
38*61 
3*9 
•77082 
28*40 
31-61 
32*11 
37*48 
4-0 
•77820 
27-60 
30-72 
31*21 
36-43 
