The piece was usually put on a traversing gun carriage that could be pointed in any direction in a full circle. They could be a stand-alone work, or be coordinated with other defensive measures. Coastal defence ordnance was normally, but not always, of the iron naval type. The gun carriages used with the ordnance could be of several types, including the standard naval gun carriage of the truck type, the traversing carriage, or the older slide carriage. Mortars could also be used in the defence of ports and naval bases. 

There were generally four types of  artillery pieces weapons pieces used on Martello Towers in the 18th and 19th centuries:

The most commonly used in England was the 24 pounder cannon, but some had 32 pounders. Some of the large towers had more than one cannon and/or one or two howitzers.

There was usually a considerable gap (known as windage) between the ball and the inside of the gun barrel, as a result of irregularities in the size of cannonballs and the difficulty of boring out gun barrels. The windage of a cannon was off as much as a quarter of an inch and caused a considerable loss of projectile power. The manufacturing practices introduced by the Carron Company reduced the windage considerably. Despite the reduced windage, carronades had a much shorter range than the equivalent long gun, typically a third to a half, because they used a much smaller propellant charge (the chamber for the powder was smaller than the bore for the ball). 

Other armaments were the firearms used by the soldiers and militia manning the towers, with the Infantry Musket being the most common.

The Cannon

The Cannon is characterized by a longer barrel, larger propelling charges, smaller shells, higher velocities, and flatter trajectories,

The 24 pounder/32 pounder cannon on the gun platform of a Martello Tower was a typical cannon of the time, used both by the Army and on the Royal Naval ships.

The cannon was muzzle loading, weighed about 2.5 tons and had a range of about a mile. Its main charges were a solid shot, canister shot or case shot, grapeshot or shrapnel.

 Find out more about the Cannon

A 24 Pounder Cannon on Martello Tower No.24

The Carronade

A carronade was much shorter and a third to a quarter of the weight of an equivalent long gun. It was was designed as a short-range naval weapon with a low muzzle velocity for merchant ships. It had a shorter barrel than the cannon and used less gunpowder.

It was as the main armament in some Martello Towers, given its effectiveness at close range, loaded with musket balls, grapeshot, lengths of chain and scrap.

NB. This is a photo of a carronade on board HMS Victory today.
It is typical of19th century carronades used in Martello Towers

Typical Carronade

The Howitzer

The Howitzer is characterized by a relatively short barrel and the use of comparatively small propellant charges to propel projectiles over relatively high trajectories, with a steep angle of descent.,

The Howitzer shown on the right is of the type designed by General Blomfield in the 19th century for use on Martello Towers in England during the Napoleonic Wars. They typically had a range of just under a mile. 

NB. This Howitzer came from on a Martello Tower on Romney
Marsh in Kent and is located in LIttlestone.
The carriage shown is not the original
but a skeleton carriage of the
type used in the 19th century.

5½ inch Howitzer

The Mortar

The originality of these artillery pieces lays with their projectiles: the bombs. They were designed to fire at even higher angles of ascent and descent than the Howitzer.

12 inch Morter (Ack 1.)