British Naval Artillery

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Overview

In the 1750s, British cannon (guns) were manufactured as 42-, 32-, 24-, 18-, 12-, 9-, 6-, 4- and 3-pounders (pdrs), the reference is to the nominal weight of the shot. Each shot would be measured against a pair of circular gauges — one maximum diameter (high gauge), one minimum diameter (low gauge). With artillery, the concept of windage is very different than that associated with rifle ballistics. Here, windage is the difference between bore diameter and shot size ― it has nothing at all to do with the atmospheric wind. Often the low gauge is the number identified as the diameter of the shot for a gun, but both elements are needed (McConnell 1988, Page 287-289). At this time, the windage was 1/20 of the width of the shot.

Although the British Army and Navy adopted very different gun patterns, Britain was careful to have their services use the same ammunition stores. In comparison, the French Navy adopted the 18-pdr, while the French Army fielded the 16-pdr. In fortifications, particularly those overseas, naval guns were often placed, not dedicated garrison guns.

Cannon lengths are measured in calibers (calibres), a single caliber being the diameter of the bore of that particular gun.

Adrian Caruana repeatedly warns in his writings that British ordnance and artillery tables had an extraordinarily long life (see Fortune 1778). What appears to be a table current to the year of publication may in reality be decades old. It is often difficult to identify the true date of the work or when it was first published or schooled. This is true for several of the tables presented in our articles on the British Artillery.

Artillery Pieces

Cannon

Muller (1768, Page xvi) advocated that the gun length of ship guns be at 15 calibers. Muller was a strong proponent of shorter iron guns. Although very influential as it regards certain aspects of gun design, Muller's recommended gun barrel lengths were not adopted and nearly all guns were longer and heavier than Muller advocated. This was especially true of naval guns were the lengths approached those of siege guns. Blomefield's large-bore naval guns of the Napoleonic Period were about 17 or 18 calibers in length, longer than recommended by Muller. The Admiralty resisted adopting shorter barrel lengths and many naval guns were between 7.5 and 9.5 feet for both hull protection and increased accuracy, regardless of shot size. If needed or desired, you could find naval 6-pdrs 9 feet in length, whereas a heavy 6-pdr field gun under Blomefield would only be about 5 feet 3 inches in length.

For many naval officers, the volume of shot in a broadside was a more important consideration than the accuracy of any single gun. As such, the speed of the reloading process was key and the shot needed to be easily loaded. Smaller windage values that might improve gun accuracy were rejected over concerns for slowing down the reloading. As gun crews were tightly packed into such tight quarters, each crew needed to learn to work smoothly together without inferring with the neighbouring crews. Daily gun drills were mandatory.

British Iron Cannon, Mid-18th Century (1743 / 1764)

Model	Barrel Weight	Barrel Length	Barrel Bore	Calibre (Ratio Length/Bore Diameter)	Shot Diameter	Charge Ratio to Weight of Shot
42-pdr	7,280 lbs 3,302.2 kg	9 ft 6 in 289.6 cm	7.018 in 17.83 cm	16.2	6.684 in 16.98 cm	2/5
32-pdr	6,140-6,160 lbs 2,785.1-2,794.1 kg	9 ft 6 in 289.6 cm	6.410 in 16.28 cm	17.8	6.105 in 15.51 cm	2/5
24-pdr	5,530-5,490 lbs 2,508.4-2,490.2 kg	9 ft 6 in 289.6 cm	5.823 in 14.79 cm	19.6	5.547 in 14.09 cm	1/2
24-pdr	5,320 lbs 2,413.1 kg	9 ft 274.3 cm	5.823 in 14.79 cm	18.5	5.547 in 14.09 cm	1/2
18-pdr	4,630-4,480 lbs 2,100.1-2032.1 kg	9 ft 274.3 cm	5.292 in 13.44 cm	20.4	5.04 in 12.80 cm	1/2
12-pdr	3,640 lbs 1,651.1 kg	9 ft 274.3 cm	4.623 in 11.74 cm	23.4	4.403 in 11.18 cm	1/2
12-pdr	3,530 lbs 1,601.2 kg	8 ft 6 in 259.1 cm	4.623 in 11.74 cm	22.1	4.403 in 11.18 cm cm	1/2
12-pdr	3,280 lbs 1,487.8 kg	7 ft 6 in 228.6 cm	4.623 in 11.74 cm	19.5	4.403 in 11.18 cm cm	1/2
9-pdr	3,250 lbs 1,472.2 kg	9 ft 274.3 cm	4.200 in 10.67 cm	25.7	4.000 in 10.16 cm	2/3
9-pdr	3,110-3080 lbs 1,410.7-1,397.1 kg	8 ft 6 in 259.1 cm	4.200 in 10.67 cm	24.3	4.000 in 10.16 cm	2/3
9-pdr	2,970 lbs 1,347.2 kg	8 ft 243.8 cm	4.200 in 10.67 cm	22.8	4.000 in 10.16 cm	2/3
9-pdr	2,740 lbs 1,242.8 kg	7 ft 6 in 228.6 cm	4.200 in 10.67 cm	21.4	4.000 in 10.16 cm	1/2
9-pdr	2,580 lbs 1,170.3 kg	7 ft 213.4 cm	4.200 in 10.67 cm	20.0	4.000 in 10.16 cm	1/2
6-pdr	2,690 lbs 1,220.2 kg	9 ft 274.3 cm	3.668 in 9.32 cm	29.4	3.498 in 8.88 cm	1/2
6-pdr	2,580 lbs 1,170.3 kg	8 ft 6 in 259.1 cm	3.668 in 9.32 cm	27.8	3.498 in 8.88 cm	1/2
6-pdr	2,460 lbs 1,115.8 kg	8 ft 243.8 cm	3.668 in 9.32 cm	26.2	3.498 in 8.88 cm	1/2
6-pdr	2,300 lbs 1,043.3 kg	7 ft 6 in 228.6 cm	3.668 in 9.32 cm	24.5	3.498 in 8.88 cm	1/2
6-pdr	2,630-2,130 lbs 1,192.9-966.2 kg	7 ft 213.4 cm	3.668 in 9.32 cm	22.9	3.498 in 8.88 cm	1/2
6-pdr	2,020 lbs 916.3 kg	6 ft 6 in 198.1 cm	3.668 in 9.32 cm	21.3	3.498 in 8.88 cm	1/2
6-pdr	1,850 lbs 839.2 kg	6 ft 182.9 cm	3.668 in 9.32 cm	19.6	3.498 in 8.88 cm	1/2
4-pdr	1,370 lbs 621.4 kg	6 ft 182.9 cm	3.204 in 8.14 cm	22.5	3.053 in 7.75 cm	1/2
4-pdr	1,260 lbs 571.5 kg	5 ft 6 in 167.6 cm	3.204 in 8.14 cm	20.6	3.053 in 7.75 cm	1/2
3-pdr	1,950 lbs 884.5 kg	6 ft 6 in 198.1 cm	2.913 in 7.40 cm	26.8	2.775 in 7.05 cm	1/2
3-pdr	812 lbs 368.3 kg	4 ft 6 in 137.2 cm	2.913 in 7.40 cm	18.5	2.775 in 7.05 cm	1/3

Source: McConnell (1988, Pages 392, 397, 401 and 411). Single Weights = Establishment of 1764. Lavery (1987, page 135)

Double Weight Entries = Measurements of 1743 / Establishment of 1764.
Measurements of 1743 derived from the Glegg Notebook ≈ 1752.
The 6.5 ft. long iron 3 pdr. was not included in the Establishment of 1764.
Shot Diameter is the Low-Gauge Value.

The 42- and 32-pdrs were naval guns that were also positioned in important fortifications such as Gibraltar. At the Sieges of Louisbourg (1758) and Québec (1759), the British Navy off-loaded both 32-pdrs and their gun crews for use in the operations. In the first half 1700s, the British Navy replaced their iron 18-pdrs with 24-pdrs. In the mid-1700s, the 18-pdr remained in the naval inventory as an uncommon iron gun. In the second half of the 18th century, the 18-pdr would again be adopted by both for the new frigate designs.

Mortar

Mortars may appear to be simple, but the physics is not. Mortars were not immune to bursting or failure. The lower lip of the bore was subject to severe stress during firing. Long mortar bores might contribute accuracy, but the shell would then repeatedly tumble within the bore generating even more unwanted stress. The size and shape of the powder chamber was a fluid concept and a source of considerable debate and study with the ultimate goal of reducing stress on the bore walls. Mortars fired exploding shells with inserted fuses. Ideally, the shells would detonate in mid-air just before or at the instant of hitting the ground. By varying fuze lengths on the shells, some crude control of the timing of the explosion could be achieved. The construction and manufacture of fuses followed very strict protocols (Caruana, 1979). When targeting a gunpowder magazine or any casement, it was hoped that the shell would first penetrate the roof structure before exploding.

Here, damage does not correlate with muzzle velocity or range. Instead, metal shards from the shell casing and the concussive wave of the explosion would cause the damage. For air explosions and the safety of the mortar crew, the minimum workable fuse length for the larger mortars required that the mortar be at least 600 or 700 yards away from the target (Wise and Hook 1979, Page 29). The bulky and heavily reinforced 10-inch iron mortar allowed for a high gunpowder charge and had a range of 2,500 yards.

At the time of the Seven Years' War the British were utilizing a single fuse and no wadding.

If desired, the formulation inside the shell could be modified to promote the formation of fires (carcasses). Mortars were most effective in a siege; they were especially feared when arrayed against cities and structures apt to burn. Bomb ketches were specialized ships fitted with mortars, typically two 13-inch or 10-inch sea-service mortars.

Sea-service mortars were much more massive than land-service mortars allowing for heavier propellant charges, double the land mortar's weight. These sea-service mortars weighed in at some 9,200 and 4,600 pounds, respectively. The bores were both deeper and thicker. A 13-inch iron sea-service mortar had a range of 4,100 yards with a 10-inch iron sea-service mortar having a range of 3,800 yards — 1,300 yards further than the corresponding land-service mortars (Hughes 1969, Page 37). Bomb ketches were used to reduce coastal fortifications and cities. Loudoun had requested three or four bomb ketches for the Louisbourg expedition. In 1759, the British would employ three bomb ketches for the Québec expedition. Wolfe moved at least four sea service mortars, six additional 13-inch mortars, one 10-inch mortar, and six 32-pdrs to the top of Pointe-aux-Pères (opposite to Québec) and established two batteries.

British Sea Service Mortars, 1750s, Selected Pieces (1743)

Model	Barrel Weight	Barrel Length	Barrel Bore	Shell Weight	Shell Diameter	Charge	Range at 45°
13-inch Iron Mortar	9,210 lbs 4,177.6 kg	?	13 in	200 lbs 90.7 kg	12.75 in	20.7 lbs	4,100 yards 3,749 m
10-inch Iron Mortar	4,590 lbs 2.082 kg	?	10 in	93 lbs 42.2 kg	9.75 in	9 lbs	3,800 yards 3,475 m

Mortars were mounted on timber beds. Iron beds had not been introduced yet. For the larger mortars, these beds were comparable to the weight of gun carriages.

Gunpowder

With all things being equal, the longer the barrel length of a cannon, the higher the muzzle velocity and the greater the range; however, one quickly reaches a point where there is no benefit gained or there is a loss in range caused by the shot tumbling within the barrel. Within reason, the smaller the windage (the difference between the barrel diameter and the shot size), the greater the muzzle velocity and the greater the range.

Considerable effort was taken by most countries in matching the manufacturing quality of their cannon to that of their shot. The more precise and consistent the manufacturing of both the cannon and the shot, the smaller the windage that could be allowed. As such, each nation had its own standards. With some very minor variation between countries, gunpowder is a mixture of saltpeter (potassium nitrate), sulfur, and charcoal (≈ 75%, 10%, and 15%, respectively). The quality, uniformity, and fineness of the gunpowder were also factors with the British having among the best gunpowder manufacturing capabilities, using high-quality saltpeter derived from their overseas colonies, particularly India via the East India Company (Lavery 1987, Page 134; McConnell 1988, Page 274). The British were incrementally improving the quality of their gunpowder throughout the 18th century. Uniformity in grain size was particularly important as it allowed the powder to spark at the same instance. Muskets benefited with the use of a finer powder, but coarser powders were favored in larger guns. However, there was no guarantee that even British gunpowder would be of the highest quality; ensuring proper dry storage was a constant problem, particularly under damp conditions or in underground magazines. Gunpowder inventories and assessments of ship stores routinely suggested that the gunpowder was too damp to fully spark or spark simultaneously. With care, gunpowder stores could re-sifted, restoring at least some of the quality. At this time, the Board of Ordnance was not yet producing their own gunpowder or preparing the necessary charcoal. This would come at the very beginning of the 19th Century.

In 1750, the larger iron guns used a charge of 2/5 the weight of the shot, 32- and 24-pdrs. Iron 18-pdrs would have a maximum service charge of 1/2 the weight of the shot. Some iron 9-pdrs were rated at 2/3 of the shot weight. In a very broad generalization with expected exceptions (1750s), British heavy and medium cannon had a maximum service charge of 1/2 the weight of the shot, light guns 1/3 or 1/4 the weight of the shot. Proof charges would be much greater. As gunpowder formulations increased in quality during the 18th century and the windage tolerances decreased, the full charge ratio was progressively reduced to avoid overcharging and bursting the gun. By the end of the Seven Years' War, the maximum service charge on all British heavy and medium guns had been reduced to 1/3 the weight of the shot — Board of Ordnance Regulations of 1764 (Muller 1768; McConnell 1998, Pages 281, 392 - 412; Caruana 1992, Page vi).

Shot Types

British Artillery Ammunition 1780 is an authoritative and accessible work (Caruana, 1979). The most common ammunition was round shot, solid iron spheres. The controlling factor here was the diameter of the shot, not its weight — different ores and manufacturing methods yielded slight differences in metal density. Maximum and minimum diameters for each shot size were established and all shot would be measured against a pair of circular gauges, the high and low gauges. Shot could be decades old or show signs of rust and corrosion, but the gauges allowed quick verification even on campaign or on ship. Solid shot was cast, then reheated and forged over to reduce irregularities.

Canister shot (case shot) was an anti-personnel projectile. It was the next most common ammunition; tin or tinned iron canisters containing small shot packed in sawdust. Sea service and land service used different sizes and numbers of shot. The number and size of the shot varied ― a 6-pdr would have some 56 shot per case; a 24-pdr having some 85 shot per case; and a 32-pdr some 72 shot per case (land service). As the canister was tinned on the outside, it could be used with brass or iron pieces, guns or howitzers. There is some evidence that canisters were sometimes made out of copper.

Canister Shot (Case Shot), Sea Service

	42-pdr	32-pdr	24-pdr	18-pdr	12-pdr	9-pdr	6-pdr	4-pdr	3-pdr
Number shot	47	56	42	42	42	44	40	28	31
Weight (ozs)	13.125	8	8	6	4	3	2	2	1.5
Diameter (in)	1.8	1.53	1.53	1.39	1.21	1.10	0.96	0.96	0.87

Note: in comparison, the Brown Bess Infantry Musket fired a lead bullet of 0.69 inches in diameter. Derived from Carauna (1979, Page 15). Diameter calculations per this author.

Grapeshot was similar, but with larger balls. It was an arrangement of 9 larger iron shot set around a wooden spindle that was attached to a round wooden base of a specified diameter. It was then placed in a bag and tied in a specific pattern to secure the shot to the spindle. Iron ordnance cannon could fire grapeshot.

Grape Shot - 9 Balls per Round, Iron Ordnance and Brass Howitzers (1780)

	42-pdr	32-pdr	24-pdr	18-pdr	12-pdr	9-pdr	6-pdr	How 5½-in	4-pdr	3-pdr
Weight (ozs)	4	3	2	1.5	1	0.8125	0.5	0.4375	0.375	0.25
Diameter (in)	3.05	2.77	2.42	2.2	1.92	1.8	1.52	0.144	1.38	1.21

Note: grape shot not used with brass cannon. Derived from Caruana (1979, Page 18). Diameter calculations per this author.

Although round shot was the most common shot, naval ammunition stores also included a wide array of specialized shot designed to remove rigging and sails ― e.g., bar shot, chain shot, and link shot (see Henry and Delf 2004, Page 32).

Both the army and navy could use either grapeshot or canister shot; navy ammunition stores strongly favored grapeshot while army stores favored canister shot. Maximum range was limited to no more than 300 yards for small bore guns, 500 yards for larger bore guns. Packaged shot was much more effective at ranges under 200 yards.

For heavy guns, the shot and powder were loaded separately. Based on intent, the gunner or officer in charge could determine what the gunpowder charge would be for the shot.

Firing Procedures

No information available yet

Iron Barrels

In the mid-18th century, much of the iron ordnance manufacture was moved to Scotland from southeast England. This required many changes in gun manufacturing as the local ores were more difficult to deal with and innately more brittle (Caruana 1989, Page 13). The obvious shortcoming of iron guns was that they rusted, whereas brass guns did not. Both guns could burst, but the busting was "controlled" in brass guns. Iron guns were much more prone to catastrophic failure. Yet when needed, iron guns could be fired at higher rates than brass guns and at higher charges (greater range). To safeguard the gun crews from catastrophic failures, the barrel walls and reinforcements were thicker on iron pieces than the corresponding brass pieces with this added metal explaining why the lighter density cast-iron guns weighed more than the brass pieces of the same length and caliber.

Traditionally, brass guns were at least 5-20% lighter in weight than the corresponding iron guns of the same bore and length. As such, they were strongly favored on the upper decks of ships, but the monetary cost was too great and the idea was abandoned in the late 1600s (Lavery 1987, Page 87).

Due to the cost of the ores involved, brass (bronze) guns were many times more expensive to produce. Muller (1768, Page 53) states for the cost of a single set of brass guns, nine sets of iron guns could be manufactured, but these iron gun sets appear to be of shorter barrel lengths. In the end, the keen desire for brass guns was mitigated by the expense. For warships in the 17th century, the cost of brass guns might be a full third of the entire cost to build a large warship. By 1700, only the very largest warships were fitted with brass guns (Lavery 1987, Page 87). To supply brass guns to the very largest ships, any brass guns that could be found on smaller vessels or in land service were transferred. Muller (1768) was a keen proponent of iron over brass both because of manufacturing costs and several elements related to gun performance, particularly overheating under rapid and continuous use. Period warships had an expected lifetime of maybe 15-years before the ship needed to be retired, so if well maintained, iron guns were not necessarily a poor match in this regard; if needed, these guns could easily be replaced.

Iron guns needed to be parked and maintained with a dry bore, the vent sealed and protected, the bore capped (tompions), and the barrel orientated slightly downward so that the gun would drain. If water was allowed into the barrel, iron guns would rust, lose metal, and honeycomb. Promoting drainage and some method for allowing atmospheric gas exchange were key. At sea, an oiled shot could be placed inside the barrel and the bore capped; as the ship pitched, the rolling shot would lubricate the bore. Freeze-thaw cycles and saltwater were especially problematic. Over time, loss of metal surrounding the powder chamber and vent was a certain problem (internal to the barrel, first reinforcement).

Furthermore, iron guns could not be recast into a new pattern and the guns would accumulate in inventories. British colonies would routinely hold onto any guns that could be acquired, but then fail to maintain the guns. Lacking maintenance, iron guns rusted and were subject to bursting, but a rusted gun was better than no gun at all.

Muller's views on the merits of iron guns were not universal and often rejected. Often his "new" pieces were never actually put into service; "proposed" would have been the better word. In this regard, care is needed when referencing Muller's writings.

Gun Carriages

The weights of naval truck carriages for 32-, 12-, and 6-pdrs were some 1,012, 672, and 308 pounds, respectively (McConnell 1988, Page 432; from Adye 1801). For the revised edition (Adye 1813), these same naval truck carriages are listed as 1,710, 1,320, and 1,040 pounds, respectively (McConnell 1998, Page 433; from Adye 1813).

References

Adye, Ralph Willet. 1802. The Bombardier and Pocket Gunner. Printed for T. Egerton, Military Library, Whitehall. By W. Blackader, Took's Court, London. Online.

Caruana, Adrain. 1979. British Artillery Ammunition, 1780. Museum Restoration Service. Bloomfield, Ontario.

Caruana, Adrain. 1989. British Artillery Design in British Naval Armaments, ed. Robert D. Smith. Royal Armouries, Conference Proceedings 1. London.

Caruana, Adrain. 1992. Introduction: The Artillerist's Companion 1778 by T. Fortune. Museum Restoration Service. Bloomfield, Ontario.

Fortune, T. 1778. The Artilleriʃt's Companion, containing the Diʃcipline, Returns, Pay, Proviʃion, &c. of the Corps, in Field, in Forts, at Sea, &c. Forward by Adrian Caruana. Museum Restoration Service, 1992. Bloomfield, Ontario.

Henry, Chris and Brian Delf. 2002. British Napoleonic Artillery 1793 - 1815 (1): Field Artillery. Osprey Publishing Ltd. Oxford.

Henry, Chris and Brian Delf. 2004. Napoleonic Naval Armaments, 1792-1815. Osprey Publishing Ltd. Oxford.

Hughes, B.P. 1969. British Smooth-Bore Artillery. Stackpole Books, Harrisburg, Pennsylvania.

Lavery, Brian. 1987. The Arming and Fitting of English Ships of War, 1600-1815. Conway Maritime Press. London.

Lavery, Brian. 1989. Carronades and Blomefield Guns: Developments in Naval Ordnance, 1778-1805. In: British Naval Armaments; Edited by Robert D. Smith. Royal Armouries, Conference Proceedings 1. London.

McConnell, David. 1988. British Smooth-Bore Artillery: A Technological Study to Support Identification, Acquisition, Restoration. Reproduction, and Interpretation of Artillery at National Historic Parks in Canada. Minister of Supply and Services Canada. Available Online.

Muller, John. 1768. A Treatise of Artillery. John Millan, Whitehall, London. Online. (First edition is 1757, available online as well. Not identical, notable in the Introduction).

Wise, Terence and Richard Hook. 1979. Artillery Equipments of the Napoleonic Wars. Osprey Press. London.

Acknowledgments

Ken Dunne for the initial version of this