62 
PRINCIPLES OF GUNNERY. 
Some experiments carried out by the Committee on Explosives with 
the 38-ton gun, with cubical powder, will serve to illustrate these 
principles:— 
Table showing 'Experiments with 38 -ton Gun , allowmg air-space . 
(Cubical powder, 1*5 ins.) 
Number 
of 
round. 
Charge. 
Shot. 
Muzzle 
velocity. 
E, 
Energy. 
P, 
Mean press, in 
powder-chamb. 
per sq. in. 
E 
P 
Length of 
cartridge. 
Cubic ins. 
per pound 
of powder. 
lbs. 
lbs. 
f.s. 
ft. tons. 
tons. 
ins. 
1 
130* 
800 
1451 
11655 
24-5 
476-9 
28-00 
24-6 
2 
130* 
800 
1391 
10734 
19-3 
556-1 
33-22 
30-0 
3 
180* 
800 
1541 
13176 
22*4 
587-3 
45-37 
30-0 
4 
180f 
800 
1544 
13225 
20-8 
634-0 
36-25 
30-0 
* Gun unchambered. f Gun chambered. 
When cubical powder is rammed up hard, each pound of powder 
occupies about 24’6 cub. ins. : any additional cubic space occupied 
shows that a certain amount of air-space has been given. The most 
suitable amount of air-space depends upon the system of rifling adopted, 
the nature of the powder, the weight of charge and projectile, and must 
be experimentally determined. With Woolwich guns and cubical 
pebble, the most suitable amount of air-space has been found to vary, 
under present conditions, from 30 to 34 cub. ins. per pound of powder.* 
The effect of allowing air-space is well shown by comparing rounds 
(1) and (2) in the above table. In round (1) the charge is rammed 
up hard; in round (2) air-space is given, allowing 30 cub. ins. for 
each pound of powder. The result is that both energy and pressure 
are reduced, but the ratio of energy to pressure is increased—which 
is important. 
The column -p represents the ratio of energy of projectile to the 
mean pressure per square inch in the powder-chamber; and the 
greater this ratio is (while the pressure, P, is kept within safe limits), 
the more effective is the gun. 
Round (3) shows how, under similar conditions of cubic space per 
pound of powder, the charge may be increased, and consequently the 
energy of the projectile, while the mean pressure in the powder- 
chamber is kept within safe limits. The cartridge is rather long— 
which is a disadvantage, as it has been found that there is a danger 
in firing very long cartridges (even when air-space is given) of 
setting up wave action } which increases the local pressure in the 
powder-chamber abnormally. It becomes, therefore, of considerable 
importance, when very large charges are fired, to chamber the gun— 
i.e.j to increase the diameter of the powder-chamber, and so to reduce 
the length of the cartridge and the pressure in the chamber. 
Round (4) shows the advantage of enlarging the chamber. The 
weight of charge and projectile are the same as in round (3), but the 
* It is not improbable, under certain conditions, that the amount of air-space may yet be stilt 
more increased, 
