The Development of Armor-piercing Shells (With Suggestions for Their Improvement)

Historical
The manufacture of projectiles to meet the requirements of the modern science of warfare has been brought to its present high stage of development through a long series of experiments based, at first, more upon theory than perhaps any other branch of engineering.
In the days of wooden vessels very little thought was given to the actual physical properties of the then cast iron spherical mass. The gun was the agent upon which depended the ability of the projectile to penetrate. The projectile, being confronted by so slight a resisting material as wood, was distorted or physically affected to practically no degree by the resisting medium. When fighting yard-arm to yard-arm the power of the gun was sufficient to fully penetrate the enemy, while at long ranges considerable damage would be executed without in the least impairing, by the shock of impact (which was inconsiderable as compared with modern conditions) the physical condition of the shot.
In the days of the all-wood vessel the guns were of the smooth-bore class divided into various types with nomenclature according to the size or weight of the shot, very much as they are today, i.e., 3-pounder, 6-pounder, 4-inch, 10-inch, etc.
A general review of the gradual development of projectiles will be found beneficial and helpful to a more complete understanding of the complexities involved in overcoming the present day difficulties.
In the smooth-bore gun spherical shot was used. This was by no means a tight fitting device. Upon firing the gun considerable powder pressure was lost through the rapid escape of the gases past the shot between it and the bore of the gun. This would most naturally be expected since at best the surface of contact between the shot and the bore would be only a circular line quickly eliminated or worn away through friction under the high temperature of the burning gases behind the shot. The most obvious way to eliminate that wearing away of the bearing surface was to increase it, in doing which the escape of gas past the projectile would be greatly checked, and the gas pressure behind the projectile increased (exerting, thereby, a greater propelling force) and imparting to the projectile greater velocity, increased momentum, and consequent increased penetration. But an increase in the bearing surface of the shot necessitated an alteration in its shape introducing difficulties affecting the accuracy of its passage through the air.