A TALK ON BIG GUNS
The First Projectiles—Introduction of Cannon—High Pressure
Guns—Machine Guns—Dimensions and Cost of Big Guns.
The first arms and machines employing gunpowder as the propelling agency, came into use in the fourteenth century. Prior to this time there were machines and instruments which threw stones and catapults and large arrows by means of the reaction of a tightly twisted rope made up of hemp, catgut or hair. Slings were also much employed for hurling missiles.
The first cannons were used by the English against the Scots in 1327. They were short and thick and wide in the bore and resembled bowls or mortars; in fact this name is still applied to this kind of ordnance. By the end of the fifteenth century a great advancement was shown in the make of these implements of warfare. Bronze and brass as materials came into general use and cannon were turned out with twenty to twenty-five inch bore weighing twenty tons and capable of hurling to a considerable distance projectiles weighing from two hundred pounds to one thousand pounds with powder as the propelling force. In a short time these large guns were mounted and carriages were introduced to facilitate transportation with troops. Meantime stone projectiles were replaced by cast iron shot, which, owing to its greater density, necessitated a reduction in calibre, that is a narrowing of the bore, consequently lighter and smaller guns came into the field, but with a greater propelling force. When the cast iron balls first came into use as projectiles, they weighed about twelve pounds, hence the cannons shooting them were known as twelve-pounders. It was soon found, however, that twelve pounds was too great a weight for long distances, so a reduction took place until the missiles were cut down to four pounds and the cannon discharging these, four pounders as they were called, weighed about one-quarter of a ton. They were very effective and handy for light field work.
The eighteenth century witnessed rapid progress in gun and ammunition manufacture. "Grape" and "canister" were introduced and the names still cling to the present day. Grape consisted of a number of tarred lead balls, held together in a net. Canister consisted of a number of small shot in a tin can, the shots being dispersed by the breaking of the can on discharge. Grape now consists of cast iron balls arranged in three tiers by means of circular plates, the whole secured by a pin which passes through the centre. The number of shot in each tier varies from three to five. Grape is very destructive up to three hundred yards and effective up to six hundred yards. Canister shot as we know it at present, is made up of a number of iron balls, placed in a tin cylinder with a wooden bottom, the size of the piece of ordnance for which it is intended.
Towards the close of the eighteenth century, short cast-iron guns called "carronades" were introduced by Gascoigne of the Cannon Iron Works, Scotland. They threw heavy shots at low velocity with great battery effect. They were for a long time in use in the British navy. The sailors called them "smashers."
The entire battery of the Victory, Nelson's famous flag-ship at the battle of Trafalgar, amounting to a total of 102 guns, was composed of "carronades" varying in size from thirty-two to sixty-eight pounders. They were mounted on wooden truck carriages and were given elevation by handspikes applied under the breech, a quoin or a wedge shaped piece of wood being pushed in to hold the breech up in position. They were trained by handspikes with the aid of side-tackle and their recoil was limited by a stout rope, called the breeching, the ends of which were secured to the sides of the ship. The slow match was used for firing, the flint lock not being applied to naval guns until 1780.
About the middle of the nineteenth century, the design of guns began to receive much scientific thought and consideration. The question of high velocities and flat trajectories without lightening the weight of the projectile was the desideratum; the minimum of weight in the cannon itself with the maximum in the projectile and the force with which it could be propelled were the ends to be attained.
In 1856 Admiral Dahlgren of the United States Navy designed the Dahlgren gun with shape proportioned to the "curve of pressure," which is to say that the gun was heavy at the breech and light at the muzzle. This gun was well adapted to naval use at the time. From this, onward, guns of high pressure were manufactured until the pressure grew to such proportions that it exceeded the resisting power, represented by the tensile strength of cast iron. When cast, the gun cooled from the outside inwardly, thus placing the inside metal in a state of tension and the outside in a state of compression. General Rodman, Chief of Ordnance of the United States Army, came forward with a remedy for this. He suggested the casting of guns hollow and the cooling of them from the inside outwardly by circulating a stream of cold water in the bore while the outside surface was kept at a high temperature. This method placed the metal inside in a state of compression and that on the outside in a state of tension, the right condition to withstand successfully the pressure of the powder gas, which tended to expand the inner portions beyond the normal diameter and throw the strain of the supporting outer layers.
This system was universally employed and gave the best results obtainable from cast iron for many years and was only superseded by that of "built up" guns, when iron and steel were made available by improved processes of production.