Smoothbore Cannons
of the Later Period

From the guns of Queen Elizabeth's time came the 6-, 9-, 12-, 18-, 24-, 32-, and 42-pounder classifications adopted by Cromwell's government and used by the English well through the eighteenth century. On the Continent, during much of this period, the French were acknowledged leaders. Louis XIV (1643-1715) brought several foreign guns into his ordnance, standardizing a set of calibers (4-, 8-, 12-, 16-, 24-, 32-, and 48-pounders) quite different from Henry II's in the previous century.

The cannon of the late 1600's was an ornate masterpiece of the foundryman's art, covered with escutcheons, floral relief, scrolls, and heavy moldings, the most characteristic of which was perhaps the banded muzzle (figs. 23b-c, 25, 26a-b), that bulbous bit of ornamentation which had been popular with designers since the days of the bombards. The flared or bell-shaped muzzle (figs. 23a, 26c, 27) did not supplant the banded muzzle until the eighteenth century, and, while the flaring bell is a usual characteristic of ordnance founded between 1730 and 1830, some banded-muzzle guns were made as late as 1746 (fig. 26a).

By 1750, however, design and construction were fairly well standardized in a gun of much cleaner line than the cannon of 1650. Although as yet there had been no sharp break with the older traditions, the shape and weight of the cannon in relation to the stresses of firing were becoming increasingly important to the men who did the designing.

18th-century cannon
FIGURE 26—EIGHTEENTH CENTURY CANNON. a—Spanish bronze 24-pounder of 1746. b—French bronze 24-pounder of the early 1700's. c—British iron 6-pounder of the middle 1700's. The 6-pounder is part of the armament at Castillo de San Marcos.

Conditions in eighteenth century Great Britain were more or less typical: in the 1730's Surveyor-General Armstrong's formulae for gun design were hardly more than continuations of the earlier ways. His guns were about 20 calibers long, with these outside proportions:

1st reinforce = 2/7 of the gun's length.
2d reinforce = 1/7 plus 1 caliber.
chase = 4/7 less 1 caliber.
 

The trunnions, about a caliber in size, were located well forward (3/7 of the gun's length) "to prevent the piece from kicking up behind" when it was fired. Gunners blamed this bucking tendency on the practice of centering the trunnions on the lower line of the bore. "But what will not people do to support an old custom let it be ever so absurd?" asked John Müller, the master gunner of Woolwich. In 1756, Müller raised the trunnions to the center of the bore, an improvement that greatly lessened the strain on the gun carriage.

Spanish 24-pounder
FIGURE 27—SPANISH 24-POUNDER CAST-IRON GUN (1693). Note the modern lines of this cannon, with its flat breech and slight muzzle swell.

The caliber of the gun continued to be the yardstick for "fortification" of the bore walls:
Vent 16 parts
End of 1st reinforce 14-1/2 do
Beginning of second reinforce 13-1/2 do
End of second reinforce 12-1/2 do
Beginning of chase 11-1/2 do
End of chase 8 do

For both bronze and iron guns, the above figures were the same, but for bronze, Armstrong divided the caliber into 16 parts; for iron it was only 14 parts. The walls of an iron gun thus were slightly thicker than those of a bronze one.

This eighteenth century cannon was a cast gun, but hoops and rings gave it the built-up look of the barrel-stave bombard, when hoops were really functional parts of the cannon. Reinforces made the gun look like "three frustums of cones joined together, so as the lesser base of the former is always greater than the greatest of the succeeding one." Ornamental fillets, astragals, and moldings, borrowed from architecture, increased the illusion of a sectional piece. Tests with 24-pounders of different lengths showed guns from 18 to 21 calibers long gave generally the best performance, but what was true for the 24-pounder was not necessarily true for other pieces. Why was the 32-pounder "brass battering piece" 6 inches longer than its 42-pounder brother? John Müller wondered about such inconsistencies and set out to devise a new system of ordnance for Great Britain,

Like many men before him, Müller sought to increase the caliber of cannon without increasing weight. He managed it in two ways: he modified exterior design to save on metal, and he lessened the powder charge to permit shortening and lightening the gun. Müller's guns had no heavy reinforces; the metal was distributed along the bore in a taper from powder chamber to muzzle swell. But realizing man's reluctance to accept new things, he carefully specified the location and size for each molding on his gun, protesting all the while the futility of such ornaments. Not until the last half of the next century were the experts well enough versed in metallurgy and interior ballistics to slough off all the useless metal.

So, using powder charges about one-third the weight of the projectile, Muller designed 14-caliber light field pieces and 15-caliber ship guns. His garrison and battering cannon, where weight was no great disadvantage, were 18 calibers long. The figures in the table following represent the principal dimensions for the four types of cannon—all cast-iron except for the bronze siege guns. The first line in the table shows the length of the cannon. To proportion the rest of the piece, Müller divided the shot diameter into 24 parts and used it as a yardstick. The caliber of the gun, for instance, was 25 parts, or 25/24th of the shot diameter. The few other dimensions—thickness of the breech, length of the gun before the barrel began its taper, fortification at vent and chase—were expressed the same way.

 
Field Ship Siege Garrison
Length in calibers 14 15 18 18
(Other proportions in 24ths of the shot diameter)
Caliber 25 25 25 25
Thickness of breech 14 24 16 24
Length from breech to taper 39 49 40 49
Thickness at vent 16 25 18 25
Thickness at muzzle 8 12-1/2 9 12-1/2

The heaviest of Müller's garrison guns averaged some 172 pounds of iron for every pound of the shot, while a ship gun weighed only 146, less than half the iron that went into the sixteenth century cannon. And for a seafaring nation such as Britain, these were important things. Perhaps the opposite table will give a fair idea of the changes in English ordnance during the eighteenth century. It is based upon John Müller's lists of 1756; the "old" ordnance includes cannon still in use during Müller's time, while the "new" ordnance is Müller's own.
Calibers and lengths of principal eighteenth century English cannon
Caliber Field Ship Siege Garrison
Iron Bronze Iron Bronze Iron Bronze Iron Bronze Iron Bronze
1-1/2 pounder
 

 

 

 

 

 
6'0"
 

 

 
3-pounder 3'6" 3'3"
 
3'6" 4'6" 3'6" 7'0"
 
4'6" 4'2"
4-pounder
 

 

 

 
6'0"
 

 

 

 

 
6-pounder 4'6" 4'1" 8'0" 4'4" 7'0" 4'4" 8'0"
 
6'6" 5'3"
9-pounder
 
4'8"
 
5'0" 7'0" 5'0" 9'0"
 
7'0" 6'0"
12-pounder 5'0" 5'1" 9'0" 5'6" 9'0" 5'6" 9'0" 6'7" 8'0" 6'7"
18-pounder
 
5'10"
 
6'4" 9'0" 6'4" 9'6" 7'6" 9'0" 7'6"
24-pounder 5'6" 6'5" 9'6" 7'0" 9'0" 7'0" 9'6" 8'4" 9'0" 8'4"
32-pounder
 

 

 
7'6" 9'6" 7'6" 10'0" 9'2" 9'6" 9'2"
36-pounder
 

 

 
7'10"
 

 

 
9'6"
 

 
42-pounder
 

 
9'6" 8'4" 10'0" 8'4" 9'6" 10'0"
 
10'0"
48-pounder
 

 

 
8'6"
 
8'6"
 
10'6"
 

 

Windage in the English gun of 1750 was about 20 percent greater than in French pieces. The English ratio of shot to caliber was 20:21; across the channel it was 26:27. Thus, an English 9-pounder fired a 4.00-inch ball from a 4.20-inch bore; the French 9-pounder ball was 4.18 inches and the bore 4.34.

The British figured greater windage was both convenient and economical: windage, said they, ought to be just as thick as the metal in the gunner's ladle; standing shot stuck in the bore and unless it could be loosened with the ladle, had to be fired away and lost. John Müller brushed aside such arguments impatiently. With a proper wad over the shot, no dust or dirt could get in; and when the muzzle was lowered, said Müller, the shot "will roll out of course." Besides, compared with increased accuracy, the loss of a shot was trifling. Furthermore, with less room for the shot to bounce around the bore, the cannon would "not be spoiled so soon." Müller set the ratio of shot to caliber as 24:25.

In the 1700's cast-iron guns became the principal artillery afloat and ashore, yet cast bronze was superior in withstanding the stresses of firing. Because of its toughness, less metal was needed in a bronze gun than in a cast-iron one, so in spite of the fact that bronze is about 20 percent heavier than iron, the bronze piece was usually the lighter of the two. For "position" guns in permanent fortifications where weight was no disadvantage, iron reigned supreme until the advent of steel guns. But non-rusting bronze was always preferable aboard ship or in seacoast forts.

Müller strongly advocated bronze for ship guns. "Notwithstanding all the precautions that can be taken to make iron guns of a sufficient strength," he said, "yet accidents will sometimes happen, either by the mismanagement of the sailors, or by frosty weather, which renders iron very brittle." A bronze 24-pounder cost £156, compared with £75 for the iron piece, but the initial saving was offset when the gun wore out. The iron gun was then good for nothing except scrap at a farthing per pound, while the bronze cannon could be recast "as often as you please."

In 1740, Maritz of Switzerland made an outstanding contribution to the technique of ordnance manufacture. Instead of hollow casting (that is, forming the bore by casting the gun around a core), Maritz cast the gun solid, then drilled the bore, thus improving its uniformity. But although the bore might be drilled quite smooth, the outside of a cast-iron gun was always rough. Bronze cannon, however, could be put in the lathes to true up even the exterior. While after 1750 the foundries seldom turned out bronze pieces as ornate as the Renaissance culverins, a few decorations remained and many guns were still personalized with names in raised letters on the gun. Castillo de San Marcos has a 4-pounder "San Marcos," and, indeed, saints' names were not uncommon on Spanish ordnance. Other typical names were El Espanto (The Terror), El Destrozo (The Destroyer), Generoso (Generous), El Toro (The Bull), and El Belicoso (The Quarrelsome One).

In some instances, decoration was useful. The French, for instance, at one time used different shapes of cascabels to denote certain calibers; and even a fancy cascabel shaped like a lion's head was always a handy place for anchoring breeching tackle or maneuvering lines. The dolphins or handles atop bronze guns were never merely ornaments. Usually they were at the balance point of the gun; tackle run through them and hooked to the big tripod or "gin" lifted the cannon from its carriage.


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