ARMOUR-PIERCING PROJECTILES. 
499 
length, and the steel shells 3*5 calibres, so that with, these two 
projectiles the weights are almost equal. In these trials Krupp 
obtained, amongst other results, the following :— 
Practice with a 6-in. (15 cm ) gun of 28 calibres in length. 
Weight of 
projectile. 
Length of 
projectile. 
Charge 
prismatic 
powder, 
density 1* 75 
Muzzle 
velocity. 
Velocity at 
1668-9 yds. 
Pressure by 
Hodman 
gauge. 
lbs. 
calibres. 
lb. 
f.s. 
f.s. 
tons. 
69*1 
2-8 
37-5 
2132-6 
1548-6 
19-05 
111*1 
4*0 
cast-iron. 
3-5 
steel. 
34-1 
1679-8 
1348-5 
17-60 
With the lengthened projectile tbe weight per unit of transverse 
section was 4*035 lb. per square inch, while with the projectile of 
2*8 calibres in length the weight did not reach 2*514 lb. per square inch. 
In order to judge of the advantage obtained by the increase of 
muzzle velocity and of the weight of the 6-in. shell, the committee 
have calculated the energy of this projectile per unit of circumference, 
and also the thickness of plate which it can perforate by direct fire. 
The results of this calculation are given in the following table :— 
Calibre. 
Eange. 
Length of 
shells. 
Muzzle 
velocity. 
Energy per 
inch of 
circumference 
Thickness of 
plate per¬ 
forated by 
direct lire. 
inches. 
yards. 
! 
calibres. 
f.s. 
f.t. 
inches. 
6 
r 
2-8 
1679-8 
39-7 
5-669 
II 
1632-8 -I 
2-8 
2132-6 
62-2 
7-126 
" 
1 
L 
3-5 
1679-8 
74-2 
7-795 
II 
1 
r 
2-8 
n 
32-5 
5-118 
II 
2332-7 -j 
! 
2-8 
2132-6 
42-5 
5-866 
II 
1 
3-5 
I 
1679-8 
61-3 
7-087 
This table shews that the increase of muzzle velocity of a 6-in. shell 
from 1679*8 to 2132*6 f.s. is sufficient to augment, by one quarter, the 
thickness of plate perforated at a range of 1632*8 yds., and by J-th the 
thickness of plate at a range of 2332*7 yds. 
