Line of Metal. The line of sight drawn directly from the breech ring to the muzzle; many early guns had fixed sights cast or attached to these positions. This was the line of sight used when firing at point-blank range, considered the effective shooting range with field and naval guns. The diameter of the muzzle was usually smaller than that of the breech ring (this difference was called the dispart), and the piece was thus slightly elevated when sighting along the line of metal.
Molding. A recess or projection, curved or rectangular, at right angles to the bore axis and cast as part of a gun tube. These were both decorative and functional, being used at points where the exterior diameter of the piece changed or where additional strength was required. The principle forms seen on ordnance of this period were the rectangular ring, the semicircular astragal, the right-angled fillet, and the reversed-curve ogee. Moldings became fewer and smaller during the late 1700s; many 19th-century artillery pieces dispensed with them entirely, or nearly so.
Mortar. A short-barreled weapon, sometimes cast integrally with its metal base and sometimes having a pair of trunnions at its breech end. Mortars were used in siege and bombardment work to "lob" explosive shells in a high, arching trajectory. Mortars did not have the mobility of the gun or the howitzer, but their ability to "drop" shells at high angles made them valuable siege and fortress weapons. Naval mortars were mounted in special "bomb vessels" and did not have to be picked up and moved from place to place; they were, thus, usually longer and heavier than their land equivalents.
Muzzle. The opening at the forward end of the bore through which a piece is loaded. The flat forward portion of the gun tube surrounding this is the muzzle face. The forward end of the gun tube is often strengthened by a tulip-like enlargement called the muzzle swell; where a front sight, or muzzle sight, is used, this is mounted on the upper side of the swell. In some pieces, such as howitzers, a rectangular-shaped muzzle band is cast instead of a swell for reinforcement.
Muzzle Velocity. The speed, expressed in feet per second, of a projectile as it leaves the muzzle of a weapon; in current artillery terminology this is call initial velocity. Muzzle velocity is the highest velocity attained by a projectile; its speed drops off as it travels, particularly in the case of old-style round shot whose form offered considerable resistance to the friction of the atmosphere.
Ogee. A molding in the form of a reversed curve; that is, having a profile in the form of the letter S. An ogee is often used at the junction of two portions of a gun tube with differing diameters, or it may be used with a ring as a fillet is used with an astragal.
Point-blank. The range at which the projectile strikes the ground, or drops below the axis of the gun bore (the latter definition was often used with naval guns, mounted some distance above the water's surface), when the piece firing it is sighted along the line of metal; that is, directly along the upper line of the gun tube from breech to muzzle. This was usually considered the effective shooting range, particularly for field or naval service, as compared to random firing.
Preponderance. The difference in weight between the breech end of a gun tube, aft of its trunnions, and forward end. Preponderance was important to designer and gunner alike; breechheaviness made the gun sit properly on its carriage and kept it form capsizing when it fired.
Quoin. Wedge set beneath the breech of a gun and moved in or out to adjust elevation. It was eventually superseded by the elevating screw. Sometimes spelled coin in contemporary works.
Random. Term applied to ranges beyond point-blank, or to firing at such ranges. Accuracy -- a relative term at best -- of smoothbore artillery began to drop off sharply as a gun was elevated and could not be predicted with anything like certainty except in such leisurely circumstances as siege or garrison work, hence the very literal use of the word random in references to shooting at longer ranges. Because of this loss of accuracy, most gun carriages of this time did not permit more than a few degrees of elevation; howitzer carriages permitted somewhat more.
Range. The horizontal distance between a gun and its target, or the distance at which a piece can hurl its projectile. To this day, there is a difference between the maximum range and effective range, the latter being the range at which reasonable accuracy and effect can be counted on. With smoothbore artillery, the difference between the two -- random and point-blank ranges -- was marked. Firing ranges had to be estimated, since rangefinders did not exist at this time. Ranges were roughly expressed in such terms as "pistol shot" (about 50 yards); "musket shot" (200-300 yards); or "cannon shot" (1,000-1,500 yards). Fractions of these terms, such as "half-pistol shot," were also used.
Reinforce. The portion of the barrel between the breech ring and the chase, extending forward past the trunnions. Since powder pressure was greatest toward the breech, this part of the gun tube was thicker than the chase. Howitzers and mortars had one reinforce, as did some guns. Other guns had two. The heavier breech reinforce is called the first reinforce; the lighter one, between the first reinforce and the chase, is the second reinforce.
Rifling. Arrangement of spiral grooves cut or cast into the bore of a piece to impart an axial spin to its projectile, thus giving it directional stability and greater accuracy. The raised sections between grooves are called lands, and the caliber of a rifled weapon is measured from land to land rather than groove to groove. Early rifled artillery pieces were muzzle-loaders; some were manufactured as rifles while others were older smoothbores modernized by having grooves cut into their bores. Since fire control was still quite primitive in the 19th century, there was still a gap of some size between maximum ranges and practical shooting ranges. The theoretical accuracy of a rifled gun was much greater than the capability of the means available to control its fire, except in such special situations as fortress or siege firing.
Rimbase. A stepped "shoulder" at the base of a trunnion where it joins the gun tube. Some pieces, as seen in the Leutze Park collection, had what were called trunnion sights, set to one side of the gun with the front sight mounted on the rimbase rather than on the muzzle. All trunnions did not have rimbases.
Ring. A rectangular molding, sometimes used with an ogee.
Shell. An explosive projectile, made of cast iron filled with black powder. Smoothbore weapons fired spherical shells; rifled guns and some later smoothbores used elongated projectiles. Round shells used simple powder-train time fuzes. Since the direction of impact of a cylindrical rifled shell could be approximated, fuzes used in such rounds were also designed to detonate on impact.
Shot. A solid round projectile, of stone or cast iron, used in smoothbore muzzle-loading artillery. The solid shot used in rifled muzzle-loaders were cylindrical and fitted with an expanding base or band so that they could be rammed down the bore from the muzzle and yet grip the rifling on firing. Smoothbore guns long fired only solid shot, while mortars and howitzers used explosives shells. Later guns used shells as well; these were called "shell guns" to distinguished them from the earlier "shot guns." The caliber of a shot gun was expressed as the weight of its shot (e.g., 6-pounder), while shell-firing ordnance was identified by bore diameter.
Shrapnel. Frequently called spherical-case shot, this was an iron shell containing a number of canister-sized balls with a black-powder bursting charge and a powder-train time fuze. It was fired and exploded in the same manner as a conventional shell but when detonated scattered its small shot as well as the iron fragments of the shell itself. This ammunition was used by the British as early as 1808, but was not given its inventor's name until the 1850s. Shrapnel rounds were used in modern steel breechloading artillery well into the 20th century.
Sight. A device used to aim a piece at its target. These may be fixed or adjustable, and may be mounted over the centerline of the gun bore or offset to one side. Fixed rear sights were usually cast or permantently mounted on, or just forward of, the breech ring. Adjustable rear sights were normally dismountable, carried separately and installed when preparing to fire. Front sights were fixed (non-movable), mounted at the muzzle or on the right rimbase, depending on the type of sight arrangement used. All of these sights were metallic. Telescopic gun sights were not introduced until steel breechloading rifled artillery came into use in the late 1800s. High-angle mortars did not use sights; the wooden carriage of a mortar was first leveled, and the mortar was then aligned with the target in train with the help of a plumb line. The weight of the powder charge was varied to adjust the weapon in range. Some gun sights were mounted on a base, of varying shape, cast as part of the gun tube or fastened to it. This sight base was called a sight piece in the early United States Army; the Navy referred to it as a sight mass.
Trajectory. The curving path followed by a projectile from muzzle to target. Guns fired their shot at higher velocities, at relatively flatter trajectories, while low-velocity mortars had high trajectories.
Trunnion. Twin cylindrical projections, cast as part of a gun tube and projecting to left and right at right angles to the bore, slightly forward of the center of gravity. The trunnions supported the weight of the guns as it rested on its carriage, and the piece pivoted on them as it was raised or lowered in elevation. Placing trunnions forward of the center of balance (4/7 of the distance from breech to muzzle was an 18th-century rule of thumb) placed the preponderance of tube weight at the breech end and kept the piece stable when fired.
Vent. The narrow opening leading from the upper side of the breech to the after end of the chamber, used for igniting the powder charge to fire the piece. Earlier guns were primed with loose powder, and their vents are often surrounded by cup-shaped moldings to receive powder. Later guns used priming tubes, and their vent openings are flush with the barrel. Hot powder gases are highly erosive, and the vents of bronze guns were enlarged by repeated firing. In later bronze guns, a cooper vent bushing, or vent piece, was screwed into a threaded socket. When the vent became enlarged. the bushing was replaced.
Windage. The difference between the bore diameter of a smoothbore artillery piece and the size of its shot or shell. Windage facilitated loading for the muzzle and allowed for black-powder fouling during firing as well as for irregularities in casting iron shot or forming stone ones. By the 18th century, windages were being standardized; Muller, in 1780, describes the bores of English ordnance as being made with a windage of 1/20 the diameter of their shot. A 6-pounder gun fired a 3.498" shot form a 3.668" bore; a 32-pounder had a 6.410" bore and used a 6.105" shot. Though windage had its justifications, it further impaired accuracy since the loose fit of a round shot made it tend to "carom" from side to side as it went down the bore of a gun and emerge from the muzzle with an inherent "wobble" in its flight which increased with range.