Carronade

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68-pounder British naval carronade, with slider carriage, on HMS Victory

The carronade is a short smoothbore, cast iron cannon, which was used by the Royal Navy and first produced by the Carron Company, an ironworks in Falkirk, Scotland, UK. It was used from the 1770s to the 1850s. Its main function was to serve as a powerful, short-range anti-ship and anti-crew weapon. While considered very successful early on, carronades eventually disappeared as rifled naval artillery changed the shape of the shell and led to fewer and fewer close-range engagements.

History[edit]

The carronade was designed as a short-range naval weapon with a low muzzle velocity for merchant ships, which found a niche role on warships. It was produced by the Carron ironworks and at first sold as a system with the gun, mounting and shot all together. The standard package of shot per gun was 25 roundshot, 15 barshot, 15 double-headed shot, 10 "single" grapeshot and 10 "single" canister shot. Single meant the shot weighed the same as the roundshot, some other canister and grapeshot were also included which weighed one and a half times the roundshot. The advantages for merchant ships are described in an advertising pamphlet of 1779.[1] Production of both shot and gun by the same firm immediately allowed a reduction in the windage, the gap between the bore of the gun and the diameter of the ball. The mounting, attached to the side of the ship on a pivot, took the recoil on a slider. The reduced recoil did not alter the alignment of the gun. The smaller gunpowder charge reduced the guns' heating in action. The pamphlet advocated the use of woollen cartridges, which, although more expensive, eliminated the need for wadding and worming. Simplifying gunnery for comparatively untrained merchant seamen in both aim and reloading was part of the rationale for the gun. The replacement of trunnions by a bolt underneath, to connect the gun to the mounting, reduced the width of the carriage enhancing the wide angle of fire. A merchant ship would almost always be running away from its target, so a wide angle of fire was much more important than on a warship. A carronade weighed a quarter as much and used a quarter to a third of the gunpowder charge for a long gun firing the same cannonball.[2] Its invention is variously ascribed to Lieutenant General Robert Melville in 1759, or to Charles Gascoigne, manager of the Carron Company from 1769 to 1779. In its early years the weapon was sometimes called a "mellvinade" or alternatively, a "gasconade".[3] The carronade can be seen as the culmination of an evolutionary process of naval guns reducing the barrel length and gunpowder charge. The Carron Company was already selling a "new light-constructed" gun, two-thirds of the weight of the standard naval gun and charged with one sixth of the weight of ball in powder before it introduced the carronade, which further halved the gunpowder charge.[1]

The reduced charge allowed carronades to have a shorter length and much lighter weight than long guns. Inside the gun barrel, increasing the size of the bore, and ball, reduces the required length of barrel. The force acting on the ball is proportional to the square of the diameter while the mass of the ball rises by the cube, acceleration is slower; the barrel can be shorter and therefore lighter. Long guns were also excessively heavy in comparison to a carronade because they were over-specified, being capable of being double shotted whereas to do this in a carronade was dangerous. A ship could carry more carronades, or carronades of a larger caliber, than long guns, and carronades could be mounted on the upper decks, where heavy long guns could cause the ship to be top-heavy and unstable. Carronades also required a smaller gun crew, which was very important for merchant ships, and they were faster to reload.

Carronades initially became popular on British merchant ships during the American Revolutionary War. A lightweight gun that needed only a small gun crew and was devastating at short range was a weapon well suited to defending merchant ships against French and American privateers. In the Action of 4 September 1782, the impact of a single carronade broadside fired at close range by the frigate HMS Rainbow under Henry Trollope caused a wounded French captain to capitulate and surrender the Hebe after a short fight.[4]

The Royal Navy was initially reluctant to adopt the guns, mainly due to mistrust of the Carron Company, which had developed a reputation for incompetence and commercial sharp practice.[5] Carronades were not even counted in numbering the guns of a ship. It was Lord Sandwich who eventually started mounting them in place of the light guns on the forecastle and quarterdeck of ships. They soon proved their effectiveness in battle. French gun foundries were unable to produce equivalents for twenty years,[5] so carronades gave British warships a significant tactical advantage during the latter part of the 18th century — though French ships mounted another type of weapon in the same role, the obusier de vaisseau. HMS Victory used the two 68-pounder carronades which she carried on her forecastle to great effect at the Battle of Trafalgar, clearing the gun deck of the Bucentaure by firing a round shot and a keg of 500 musket balls through the Bucentaure's stern windows.

The carronade was initially very successful and widely adopted, and a few experimental ships (for example, HMS Glatton and HMS Rainbow[5]) were fitted with a carronade-only armament. Glatton, a fourth-rate ship with 56 guns, had a more destructive broadside than HMS Victory, a first-rate ship with 100 guns. Although Glatton and Rainbow were both successful in battle, the carronade's lack of range against an opponent who could keep well clear and still use his long guns was an arguable tactical disadvantage of this arrangement.

In the 1810s and 1820s, tactics started to place a greater emphasis on the accuracy of long-range gunfire, and less on the weight of a broadside. Indeed, Captain David Porter of USS Essex complained when the navy replaced his 12-pounder long guns with 32-pounder carronades. The carronade disappeared from the Royal Navy from the 1850s after the development of steel-jacketed cannon by William George Armstrong and Joseph Whitworth. Carronades were nevertheless still used in the American Civil War in the 1860s. The last known use of a carronade in conflict was during the First Boer War. In the siege of Potchefstroom the Boers used 'Ou Griet', an antique carronade mounted on a wagon axle, against the British fort.[6]

Design[edit]

Admiralty carriage mount for an 18-pounder carronade, 1808.

The original design of the carronade included a different type of mounting on a wooden carriage where the cannon itself had a projecting loop on the bottom that was pinned to the gun carriage, which was fastened to the side of the ship, with a pivoting mounting which allowed the gun to be rotated while rearward recoil was contained, sometimes with a slider carriage. In some versions a wedge was placed underneath the chamber to control elevation while in later versions an elevating screw was used

Carronades had a chamber one caliber smaller than the bore – for example, an 18-pounder carronade had its chamber bored equal to a 12-pounder. This was partly to reduce the weight of the cannon, but also had the effect of reducing the velocity of the cannonball and range to which it could fire, relative to a gun firing the same weight of shot, and all other things being equal. However, one factor mitigating the deficiency in range is that carronades could be bored with a much tighter windage than long guns. This meant that more of the propellant went to moving the shot, rather than bypassing it.

Naval artillery during the Age of Sail simply was not accurate, regardless of whether the cannon was a gun or a carronade. Almost all barrels were smoothbore, not rifled, and tolerances on everything from the actual roundness and straightness of the barrel and shot size in relation to the bores (windage) had wide variations. Sights were rudimentary or non-existent and elevation was controlled by wedges and guesswork. As a result, effective or decisive naval battles were generally fought at ranges under 100 yards where the carronade's heavier ball was useful and its shorter range was not a huge problem. While technological improvements changed the capabilities of naval armament by the nineteenth century, muzzle-loading smoothbore cannon were still not very accurate. As a result, shipborne cannon counted on the effect of rapid broadsides at short range. The carronade could make a significant contribution to the weight of a broadside.

Ordnance[edit]

Diagram of a carronade mounting. The lack of a nozzle or muzzle cup suggests this carronade pre-dates ca. 1790
Model of a carronade with grapeshot ammunition

A carronade was much shorter and a third to a quarter of the weight of an equivalent long gun: a 32-pounder carronade, for example, weighed less than a ton, but a 32-pounder long gun weighed over 3 tons. Carronades were manufactured in the usual naval gun sizes: 6-, 12-, 18-, 24-, 32-, and 42-pounders, and 68-pounder versions are known.

The smaller carronades served in three roles. First, they often constituted the entire armament of unrated vessels. For instance, the Ballahoo- and Cuckoo-class schooners were armed only with four 12-pounder carronades. Second, gunboats, such as those that the Americans deployed at the Battle of Lake Borgne often had one large 18-, 24-, or 32-pounder gun forward on a pivot, and two smaller carronades aft. Lastly, larger vessels carried a few 12-, 18-, or 24-pounders, to arm their ship's boats — the cutters, pinnaces, launches, barges, and the like — to give them firepower for boat actions. For instance, each of the 42 larger British boats at the Battle of Lake Borgne carried a carronade in its bows; only the three gigs were unarmed.

At the other end, even a quite small vessel might carry the 68-pounders. For instance, Commander William Layman of the ill-fated Cruizer-class brig sloop HMS Raven replaced her two forward 6-pounder guns and 32-pounder carronades with a single 68-pounder on a pivot, and then did the same with two of the aft 32-pounder carronades. By doing this he replaced 70 pounds of broadside with 136 pounds (assuming that both 68-pounders would usually fire on the same side), and ensured that Raven would have less dead-space to her front and rear.

Carronades were not counted in a ship of the line's rated number of guns. The classification of Royal Navy vessels in this period can therefore mislead; they would often be carrying fewer guns but more pieces of ordnance than they were described as carrying.

Although the carronade, like other naval guns, was mounted with ropes to restrain the recoil, the details of the gun mounting were usually quite different. The carronade was typically mounted on a sliding, rather than wheeled, gun carriage, and elevation was achieved with a turnscrew, like field guns, rather than the quoins (wooden wedges) usual for naval guns. In addition, a carronade was usually mounted on a lug underneath the barrel, rather than the usual trunnions to either side. As a result, the carronade had an unusually high centre of gravity. Towards the end of the period of use, some carronades were fitted with trunnions to lower their centre of gravity, to create a variant known as the gunnade. Gunnades, introduced around 1820, should not be confused with the earliest carronades, which also featured trunnions.

Carronade on a garrison mount, used to defend fortifications. Government House, Bermuda

Range[edit]

As a result of irregularities in the size of cannonballs and the difficulty of boring out gun barrels, there was usually a considerable gap (known as the windage) between the ball and the inside of the gun barrel. The windage of a cannon was often 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, typically a third to a half, than the equivalent long gun because they used a much smaller propellant charge (the chamber for the powder was smaller than the bore for the ball). Typical naval tactics in the late 18th century, however, emphasised short-range broadsides, so the range was not thought to be a problem.

The carronade disappeared into history before the science of aerodynamics started. At the time there was no good theory to account for the range of cannon. We now know that the air resistance of the spherical cannonball in supersonic flight is much much greater than in subsonic flight. For a given weight of powder, a larger ball, having a large mass, would have a lower maximum velocity which would reduce the range of supersonic flight. But the increase in the distance of subsonic flight, as the air resistance is proportional to the square of the diameter but the mass is proportional to the cube, may have more than compensated. Carronades were short range because of their small gunpowder charge but their lower muzzle velocity required a higher trajectory. But at sea, the range of the long gun had little use. At sea, guns were on moving platforms making timing of fire, i.e. aim in the vertical plane, very difficult. Pitch and roll meant that most ships fought at close range of a few hundred yards or less. In battles between warships, carronades could be at a disadvantage, if they were fought outside its point blank range; however, there is no evidence that any battle was decided outside of carronade range. Warships often aimed at the enemy’s hull to destroy its capacity for battle. A ball fired from a cannon, on the downward roll of the ship, would often ricochet off the sea into the enemy hull. A merchant ship would more often aim at the bigger target of the masts and rigging in the hope of escaping a pursuing enemy. The higher trajectory required for carronades, at ranges of 400 yards or more, was of little disadvantage for its use by merchant ships or any naval ship fleeing a more powerful enemy. Theory for centuries had always associated long barrels with long range but experience had also shown that shortening the barrel (e.g. the English musket barrel between 1630 and 1660 went down from 4 to 3 feet long[7]) did not reduce performance as much as expected.

Diagram[edit]

Carronade-tag.svg
  1. Breech bolt
  2. Aft sight
  3. Vent hole
  4. Front sight
  5. First reinforcing ring
  6. Barrel
  7. Muzzle
  8. Second reinforcing ring
  9. Horizontal rotation axis
  10. Chock
  11. Vertical rotation axis
  12. Wheel
  13. Mobile pedestal
  14. Carriage
  15. Pommel
  16. Elevation thread

References[edit]

Citations
  1. ^ a b . An Attempt to improve the Method of Arming Trading Vessels. With a description of the carronade, and some hints concerning shot. The third edition Falkirk, 1779.
  2. ^ p 84 J. Guillmartin "Ballistics in the Black Powder era" p 73-98 in ROYAL ARMOURIES CONFERENCE PROCEEDINGS.; British naval armament 1600-1900; London, 1987; Nov, 1989,
  3. ^ Kincaid (2007), 116.
  4. ^ "Introducing the Carronade". Age Of Sail · Life at sea during the age of wooden ships and iron men. Retrieved 15 October 2013. 
  5. ^ a b c Rodger (2004), p.420
  6. ^ [1] Major D.D. Hall: The Artillery of the First Anglo-Boer War 1880 - 1881
  7. ^ C. H. Firth Cromwell's Army 4th ed. p80
Bibliography