From the 16th to the mid-19th century, the main form of artillery remained the
smoothbore cannon. By this time, the
trunnion (a short axle protruding from either side of the gun barrel) had been developed, with the result that the barrel could be held in two recesses in the carriage and secured with an iron band, the "
capsquare". This simplified elevation, which was achieved by raising or lowering the breech of the gun by means of a wedge called a
quoin or later by a steel screw. During this time, the design of gun carriages evolved only slowly, with the trend being towards lighter carriages carrying barrels that were able to throw a heavier projectile. There were two main categories of gun carriages:
Naval or garrison carriages These were designed for use aboard a ship or within a
fortification and consisted of two large wooden slabs called "cheeks" held apart by bracing pieces called "transoms". The trunnions of the gun barrel sat on the top of the cheeks; the rearward part of each cheek was stepped so that the breech could be lifted by iron levers called "handspikes". Because these guns were not required to travel about, they were only provided with four small solid wooden wheels called "trucks", whose main function was to roll backwards with the
recoil of the gun and then allow it to be moved forward into a firing position after reloading. Traversing the gun was achieved by levering the rear of the carriage sideways with handspikes. An improvement on this arrangement started at the end of the 18th century with the introduction of the
traversing carriage, initially in fortifications but later on ships as well. This consisted of a stout wooden (and later iron)
beam on which the entire gun carriage was mounted. The beam was fitted to a
pivot at the centre, and to one or more trucks or "racers" at the front; the racers ran along a semi-circular iron track set in the floor called a "race". This allowed the gun to be swung in an arc over a
parapet. Alternatively, the pivot could be fitted to the front of the beam and the racers at the rear, allowing the gun to fire through an
embrasure. The traversing beam sloped upwards towards the rear, allowing the gun and its carriage to recoil up the slope.
Field carriages These were designed to allow guns to be deployed on the battlefield and were provided with a pair of large wheels similar to those used on
carts or wagons. The cheeks of field carriages were much narrower than those on the naval carriage and the rear end, called a "trail", rested on the ground. When the gun needed to be moved any distance, the trail could be lifted onto a second separate axle called a
limber, which could then be towed by a team of horses or oxen. Limbers had been invented in France in about 1550. An innovation from the mid-18th century was the invention of the "block trail", which replaced the heavy cheeks and transoms of the "double-bracket" carriage with a single wooden spar reinforced with iron. A curricle gun was a small cannon intended to be transported upon a carriage of two wheels; the artilleryman was sitting on a box and the whole can be moved forward into action with impressive rapidity. Its
caisson would contain 6 rounds of ball cartridges. It was current in 1800. ==Modern gun carriages==