Gunnery is the science which governs by its laws the construction and employment of all firearms, though the term 'musketry' is generally applied to the scientific use of small-arms. It involves a knowledge of the properties of metals, and details of their manipulation in gun-manufacture, as well as the calculation of the strains to which the weapon will be subjected, the velocities of projectiles, and the effect upon them of the various forces to which they are exposed in the bore of the gun and during their flight through the air.
This subject was first treated of by an Italian mathematician, Nicolas Tartaglia, who in 1537 published La Nuova Scientia. He also invented the gunner's quadrant. Many other writers followed him, of whom the principal was Galileo, whose Dialogues on Motion were printed in 1638. But the real founder of the science was Benjamin Robins (q.v.), whose New Principles of Gunnery appeared in 1742, and treated of atmospheric resistance, the force of gunpowder, the effects of varying the length and weight of guns, &c. His invention, the Ballistic Pendulum (q.v.), enabled the velocity of a cannon-ball to be measured, and was generally used for that purpose until superseded by Navez's electro-ballistic pendulum about 1862. Euler, Halton, and others added by their commentaries on Robins's work to the general knowledge of the subject which existed up to the end of the 18th century. In 1840 Professor Wheatstone invented an electric chronoscope for measuring velocities, which was followed by those of Navez-Leurs, Bashforth, Noble, and De Boulengé. In 1878-80 the Rev. F. Bashforth produced his chronograph for measuring the resistance of the air to the motion of elongated projectiles. By means of his tables and the various instruments now placed at their disposal, mathematicians are able to calculate the proper length, thickness of metal, size of chamber, charge, form of projectile and method of rotating it for a gun of given calibre, and also to determine the time of flight, penetration, height and velocity at any point, and elevation required for any range, &c. The latter are most necessary in order that the gun may be skilfully handled, and each weapon has its 'range table' made out, giving these particulars.
The official Text-book of Gunnery (1887), by Major Mackinlay, R.A., is one of the best modern treatises on this subject, and has been largely quoted in foreign works, notably in the External Ballistics of Captain Ingalls, U.S. Artillery.
In 1880 Major F. Siacci, of the Italian Artillery, put forward a method of solving trajectories and problems in ballistics, and his formulæ have been used by artillerists of all nations with very satisfactory results.
Without explaining the intricate calculations and delicate instruments used, it may be interesting to give a few examples of gunnery problems. A shot was fired at Shoeburyness in 1887, and called the Jubilee shot, from a 9.2-inch wire-gun at an angle of 40° elevation, by which it was thought an extreme range would be obtained. The calculated range was 20,765.3 yards (say 12 miles); maximum height, 17,110.6 feet; time of flight, 63.787 seconds; angle of descent, 53° 50'. The actual range was 20,236 yards.
The necessary elevation for a 12-inch 45-ton gun, firing with a charge of 295 lb. and a muzzle velocity of 1910 feet per second at a point 3000 yards distant and 1270 feet above it, is found to be 2° 25'. An 8-inch howitzer of 70 cwt. is to breach the escarp of a ditch 50 feet wide, with common shell and delay-action fuze—the angle of descent must be 14° and the striking velocity not less than 600 feet per second; required the least necessary distance of the howitzer from the escarp, the requisite charge of powder, and angle of elevation. Answer, 1936 yards, 6 lb. R.L.G.2 powder, and 13° 23'.
In designing a rifle of which the velocity is to be 800 feet per second at 1000 yards, and trajectory in no place higher than 32 feet, it is necessary to know the proportions of weight of bullet to calibre, which are found by Siacci's formulæ to be 358 grains for a calibre of .38 inch, or 254 grains for .32-inch calibre.
From these and similar examples it will be understood that gunnery has become one of the exact sciences. The excellence of modern machinery enables the manufacture of weapon, projectile, powder, and fuze to satisfy the demands of the theorists, while such inventions as Watkin's position and range finders and Scott's telescopic sights put it in the power of the trained artillerist to show equally good results in practice. See BREECH-LOADING, CANNON, RIFLE; for the School of Gunnery at Shoeburyness, see ARTILLERY.