In no case can the pressure rise in the gun
beyond that in the reservoir.
Up to the present time there have been no accidents in using the most
powerful explosives in their natural state, and in quantities over
fifty per cent. of the weight of the projectile. I have seen
projectiles weighing 950 pounds, and containing 500 pounds of
explosives (300 pounds of the blasting gelatine and 200 pounds of No.
1 dynamite) thrown nearly a mile and exploded after disappearing under
water. According to Gen. Abbot's formula such a projectile would have
sunk any armorclad floating within forty-seven feet of where it
struck. Apparently there is no limit to the percentage of explosive
that can be placed in the shell except the mechanical one of having
the walls thick enough to prevent being crushed by the shock of
discharge. In the large projectiles a transverse diaphragm is
introduced to strengthen the walls and to subdivide the charge.
The development of the pneumatic gun has been attended with some other
important discoveries, which may be of interest. It is well known that
mortar fire is very inaccurate, except at fixed long distances, in
consequence of the high angle, the slowness of flight of the
projectile, the variability of the powder pressure, and the inability
to change the elevation and the charge of powder rapidly.
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