56 
PRINCIPLES OP GUNNERY. 
The velo¬ 
city of a 
projectile 
at any 
point in 
the bore c 
a gun. 
Muzzle 
velocity. 
A comparison of this with the maximum work that could theo¬ 
retically be effected by the charge, shows that there is a deficiency of 
929 ft. tons of energy not realised in practice. This is due to the 
modifications mentioned above. The greater the weight of the pro¬ 
jectile, the more rapid the explosion of the powder, and the less the 
proportionate amount of heat absorbed by the gun, the more nearly 
will the maximum theoretical effect of the powder be realised. With 
service conditions, the heavier the gun the less the proportionate 
amount of heat absorbed. In the 9-in. gun the per-cent age of 
maximum effect actually realised is 
349400 
4423 
= 79-0. 
This is called the factor of effect for this particular gun and charge. 
Captain A. Noble has calculated the factor of effect for every gun 
and charge in the British service. A table of factors of effect is 
given in p. 354 of the “ Treatise on the Construction and Manufacture 
of Ordnance in the British Service.” 
The velocity of a projectile at any point of the bore depends on its 
weight, and upon the work done on it up to that point. By the rule 
of work, it follows that 
where W = weight of projectile, 
v — velocity at any point of the bore, 
It = work done per pound of powder on projectile up to that point, 
C — weight of charge in lbs.; 
or 
( 1 ) 
So that if the work done on a projectile at any point of the bore of 
a gun is known, its velocity at that point may be determined by 
formula (1); which, expressed in words, means that the velocity of a 
projectile at any point of the bore of the gun varies directly as the 
square root of the work done upon it up to that point, and inversely as 
the square root of its weight. 
Consequently, if V represent the muzzle velocity of the projectile, 
and K the work done on it per pound of powder up to the muzzle , 
r = . (3) 
Now, if the work done on a projectile [KC) in a gun is constant, 
the muzzle velocity of the projectile varies inversely as the square root of its 
weight; 
or 
Fa 
(3) 
But the work done on a projectile by a given charge of powder in 
the same or similar guns is slightly increased when the weight of the 
projectile is increased. For example: in the 10-in. M.L. gun, with a 
