It was found that the inner surface of the tube stretched more than the outer surface, and that after the inner surface had been stretched to its limit of elasticity the outer part failed to add to its strength, so that further thickness was of no benefit.

To do away with this condition cannon were constructed on the principle of varying elasticity, the metal with the greatest elongation within its elastic limit being placed next to the bore, yet in high-powered guns this system failed to yield the result desired and it was replaced by what is known as the initial tension system. This comprised two methods: the plain built-up gun and the wire-wound gun. In the latter certain parts of the gun were wrapped with wire in the form of a ribbon.

Rapid-Fire Gun.

Six-inch rapid-fire gun equipped with patented two-handed elevating gear, consisting of two hand wheels on opposite ends of the same shaft, the handles being 180 degrees apart. The pointer uses both hands in elevating and depressing the gun. The electric firing trigger A is worked by the index finger of the right hand without releasing the handle. There is a second firing handle B attached to the slide, for firing either electrically or percussively.

Courtesy of the Bethlehem Steel Co.