The First Epoch Early 14th Century to 1845

About the same time Charles Lancaster endeavoured to rotate projectiles by giving the gun an elliptical bore of small eccen tricity, the spiral increased gradually towards the muzzle, and rotation was effected through rifling "surfaces" instead of by grooves. Guns rifled on this principle were used in gunboats dur ing the Crimean War, but were not a success. An improved form of this principle of rifling was adopted by Joseph Whitworth a few years later. The advantages of an elongated rotating projectile both in range and penetrative properties were now thoroughly established. The muzzle velocity of guns during the last ioo years of the ist epoch compared favourably with that of the earlier rifled guns; the elongated projectiles of the latter however lost their velocity slowly whereas the smooth bore round shot lost velocity so rapidly that at 2,000 yards' range the striking velocity has only about one third of the muzzle velocity.

Introduction of Shrinkage Construction.

The idea of re inforcing cast iron or bronze guns to reduce the number of acci dents with cast pieces had been under investigation from time to time. In 1833 a gun was produced by M. Thiery (France), by whom the virtue of shrinking on hoops was to some extent appre ciated. The interior of the gun was made of cast iron, and this was encased in a longitudinal armature of wrought iron bars, which were further reinforced by wrought iron hoops shrunk on.

In 1855 W. G. Armstrong (afterwards Lord Armstrong, q.v.) designed a rifled breech-loading gun embodying so many con siderable improvements as to be in effect revolutionary. The main feature of the construction was the introduction of hoops and tubes formed by wrought iron bars, which were coiled hot on a mandril and welded into a closed helix, the fibre of the wrought iron running in the direction most suitable for circumferential strength. Longitudinal strength was obtained by a forged hollow breech piece. These helical cylinders were shrunk over a steel tube or liner in the original Armstrong gun. In later construc tion the steel tube was replaced by a wrought iron helical tube (see fig. 6). The gun was rifled with a large number of grooves and fired lead-coated projectiles, thus eliminating windage; breech-loading was effected by a powerful screw holding a sliding vent-piece tightly against the face of the breech.

Various types of guns, having a built-up form of construction involving shrunk hoops, were produced about the same period as the Armstrong gun, notably Chambers gun (United States, Treadwell gun (United States, 1855) ; Blakely gun (Britain,