Early Smoothbore Cannon

Soon after he found he could hurl a rock with his good right arm, man learned about trajectory—the curved path taken by a missile through the air. A baseball describes a "flat" trajectory every time the pitcher throws a hard, fast one. Youngsters tossing the ball to each other over a tall fence use "curved" or "high" trajectory. In artillery, where trajectory is equally important, there are three main types of cannon: (1) the flat trajectory gun, throwing shot at the target in relatively level flight; (2) the high trajectory mortar, whose shell will clear high obstacles and descend upon the target from above; and (3) the howitzer, an in-between piece of medium-high trajectory, combining the mobility of the fieldpiece with the large caliber of the mortar.

The Spaniard, Luis Collado, mathematician, historian, native of Lebrija in Andalusia, and, in 1592, royal engineer of His Catholic Majesty's Army in Lombardy and Piedmont, defined artillery broadly as "a machine of infinite importance." Ordnance he divided into three classes, admittedly following the rules of the "German masters, who were admired above any other nation for their founding and handling of artillery." Culverins and sakers (Fig. 23a) were guns of the first class, designed to strike the enemy from long range. The battering cannon (fig. 23b) were second class pieces; they were to destroy forts and walls and dismount the enemy's machines. Third class guns fired stone balls to break and sink ships and defend batteries from assault; such guns included the pedrero, mortar, and bombard (fig. 23c,d).

Collado's explanation of how the various guns were invented is perhaps naive, but nevertheless interesting: "Although the main intent of the inventors of this machine [artillery] was to fire and offend the enemy from both near and afar, since this offense must be in diverse ways it so happened that they formed various classes in this manner: they came to realize that men were not satisfied with the espingardas [small Moorish cannon], and for this reason the musket was made; and likewise the esmeril and the falconet. And although these fired longer shots, they made the demisaker. To remedy a defect of that, the sakers were made, and the demiculverins and culverins. While they were deemed sufficient for making a long shot and striking the enemy from afar, they were of little use as battering guns because they fire a small ball. So they determined to found a second kind of piece, wherewith, firing balls of much greater weight, they might realize their intention. But discovering like-wise that this second kind of piece was too powerful, heavy and costly for batteries and for defense against assaults or ships and galleys, they made a third class of piece, lighter in metal and taking less powder, to fire balls of stone. These are the commonly called cañones de pedreros. All the classes of pieces are different in range, manufacture and design. Even the method of charging them is different."

trajectories
FIGURE 22—TRAJECTORIES. Maximum range of eighteenth century guns was about 1 mile.
Guns could: Batter heavy construction with solid shot at long or short range; destroy fort parapets and, by ricochet fire, dismount cannon; shoot grape, canister, or bombs against massed personnel.
Mortars could: Reach targets behind obstructions; use high angle fire to shoot bombs, destroying construction and personnel.
Howitzers could:Move more easily in the field than mortars; reach targets behind obstructions by high angle fire; shoot larger projectiles than could field guns of similar weight.

It was most important for the artillerist to understand the different classes of guns. As Collado quaintly phrased it, "he who ignores the present lecture on this arte will, I assert, never do a good thing." Cannon burst in the batteries every day because gunners were ignorant of how the gun was made and what it was meant to do. Nor was such ignorance confined to gunners alone. The will and whim of the prince who ordered the ordnance or "the simple opinion of the unexpert founder himself," were the guiding principles in gun founding. "I am forced," wrote Collado, "to persuade the princes and advise the founders that the making of artillery should always take into account the purpose each piece must serve." This persuasion he undertook in considerable detail.

The first class of guns were the long-range pieces, comparatively "rich" in metal. In the following table from Collado, the calibers and ranges for most Spanish guns of this class are given, although as the second column shows, at this period calibers were standardized only in a general way. For translation where possible, and to list those which became the most popular calibers, we have added a final column. Most of the guns were probably of culverin length: 30- to 32-caliber.

Spanish artillery
FIGURE 23—SIXTEENTH CENTURY SPANISH ARTILLERY. Taken from a 1592 manuscript, these drawings illustrate the three main classes of artillery used by Spain during the early colonial period in the New World. a—Culverin (Class 1). b—Cannon (Class 2). c—Pedrero (Class 3). d—Mortar (Class 3).
Sixteenth century Spanish cannon of the first class
Name of gun Weight of ball
(pounds)
Length of gun
(in calibers)
Range in yards Popular caliber
Point-
blank
Maximum
Esmeril 1/2
 
208 750 1/2-pounder esmeril.
Falconete 1 to 2
 

 

 
1-pounder falconet.
Falcon 3 to 4
 
417 2,500 3-pounder falcon.
Pasavolante 1 to 15 40 to 44 500 4,166 6-pounder pasavolante.
Media sacre 5 to 7
 
417 3,750 6-pounder demisaker.
Sacre 7 to 10
 

 

 
9-pounder saker.
Moyana 8 to 10 shorter than saker
 

 
9-pounder moyenne.
Media culebrina 10 to 18
 
833 5,000 12-pounder demiculverin.
Tercio de culebrina 14 to 22
 

 

 
18-pounder third-culverin.
Culebrina 20, 24, 25, 30, 40, 50 30 to 32 1,742 6,666 24-pounder culverin.
Culebrina real 24 to 40 30 to 32
 

 
32-pounder culverin royal.
Doble culebrina 40 and up 30 to 32
 

 
48-pounder double culverin.

In view of the range Collado ascribes to the culverin, some remarks on gun performances are in order. "Greatest random" was what the old time gunner called his maximum range, and random it was. Beyond point-blank range, the gunner was never sure of hitting his target. So with smoothbores, long range was never of great importance. Culverins, with their thick walls, long bores, and heavy powder charges, achieved distance; but second class guns like field "cannon," with less metal and smaller charges, ranged about 1,600 yards at a maximum, while the effective range was hardly more than 500. Heavier pieces, such as the French 33-pounder battering cannon, might have a point-blank range of 720 yards; at 200-yard range its ball would penetrate from 12 to 24 feet of earthwork, depending on how "poor and hungry" the earth was. At 130 yards a Dutch 48-pounder cannon put a ball 20 feet into a strong earth rampart, while from 100 yards a 24-pounder siege cannon would bury the ball 12 feet.

But generalizations on early cannon are difficult, for it is not easy to find two "mathematicians" of the old days whose ordnance lists agree. Spanish guns of the late 1500's do, however, appear to be larger in caliber than pieces of similar name in other countries, as is shown by comparing the culverins: the smallest Spanish culebrina was a 20-pounder, but the French great couleurine of 1551 was a 15-pounder and the typical English culverin of that century was an 18-pounder. Furthermore, midway of the 1500's, Henry II greatly simplified French ordnance by holding his artillery down to the 33-pounder cannon, 15-pounder great culverin, 7-1/2-pounder bastard culverin, 2-pounder small culverin, a 1-pounder falcon, and a 1/2-pounder falconet. Therefore, any list like the one following must have its faults:
Principal English guns of the sixteenth century
Name Caliber
(inches)
Length Weight
of gun
(pounds)
Weight
of shot
(pounds)
Powder
charge
(pounds)
Ft. In.
Rabinet 1.0
 
300 0.3 0.18
Serpentine 1.5
 
400 .5 .3
Falconet 2.0 3 9 500 1.0 .4
Falcon 2.5 6 0 680 2.0 1.2
Minion 3.5 6 6 1,050 5.2 3
Saker 3.65 6 11 1,400 6 4
Culverin bastard 4.56 8 6 3,000 11 5.7
Demiculverin 4.0
 
3,400 8 6
Basilisk 5.0
 
4,000 14 9
Culverin 5.2 10 11 4,840 18 12
Pedrero 6.0
 
3,800 26 14
Demicannon 6.4 11 0 4,000 32 18
Bastard cannon 7.0
 
4,500 42 20
Cannon serpentine 7.0
 
5,500 42 25
Cannon 8.0
 
6,000 60 27
Cannon royal 8.54 8 6 8,000 74 30

Like many gun names, the word "culverin" has a metaphorical meaning. It derives from the Latin colubra (snake). Similarly, the light gun called áspide or aspic, meaning "asp-like," was named after the venomous asp. But these digressions should not obscure the fact that both culverins and demiculverins were highly esteemed on account of their range and the effectiveness of fire. They were used for precision shooting such as building demolition, and an expert gunner could cut out a section of stone wall with these guns in short order.

As the fierce falcon hawk gave its name to the falcon and falconet, so the saker was named for the saker hawk; rabinet, meaning "rooster," was therefore a suitable name for the falcon's small-bore cousin. The 9-pounder saker served well in any military enterprise, and the moyana (or the French moyenne, "middle-sized"), being a shorter gun of saker caliber, was a good naval piece. The most powerful of the smaller pieces, however, was the pasavolante, distinguishable by its great length. It was between 40 and 44 calibers long! In addition, it had thicker-bore walls than any other small caliber gun, and the combination of length and weight permitted an unusually heavy charge—as much powder as the ball weighed. A 6-pound lead ball was what the typical pasavolante fired; another gun of the same caliber firing an iron ball would be a 4-pounder. The point-blank range of this Spanish gum was a football field's length farther than either the falcon or demisaker.

In today's Spanish, pasavolante means "fast action," a phrase suggestive of the vicious impetuosity to be expected from such a small but powerful cannon. Sometimes it was termed a drajon, the English equivalent of which may be the drake, meaning "dragon"; but perhaps its most popular name in the early days was cerbatana, from Cerebus, the fierce three-headed dog of mythology. Strange things happen to words: a cerbatana in modern Spanish is a pea shooter.
Sixteenth century Spanish cannon of the second class
Spanish name Weight of ball
(pounds)
Translation
Quarto canon 9 to 12 Quarter-cannon.
Tercio canon 16 Third-cannon.
Medio canon 24 Demicannon.
Canon de abatir 32 Siege cannon.
Doble canon 48 Double cannon.
Canon de bateria 60 Battering cannon.
Serpentino
 
Serpentine.
Quebrantamuro or lonbarda 70 to 90 Wallbreaker or lombard.
Basilisco 80 and up Basilisk.

The second class of guns were the only ones properly called "cannon's in this early period. They were siege and battering pieces, and in some few respects were similar to the howitzers of later years. A typical Spanish cannon was only about two-thirds as long as a culverin, and the bore walls were thinner. Naturally, the powder charge was also reduced (half the ball's weight for a common cannon, while a culverin took double that amount).

The Germans made their light cannon 18 calibers long. Most Spanish siege and battering guns had this same proportion, for a shorter gun would not burn all the powder efficiently, "which," said Collado, "is a most grievous fault." However, small cannon of 18-caliber length were too short; the muzzle blast tended to destroy the embrasure of the parapet. For this reason, Spanish demicannon were as long as 24 calibers and the quarter-cannon ran up to 28. The 12-pounder quarter-cannon, incidentally, was "culverined" or reinforced so that it actually served in the field as a demiculverin.

The great weight of its projectile gave the double cannon its name. The warden of the Castillo at Milan had some 130-pounders made, but such huge pieces were of little use, except in permanent fortifications. It took a huge crew to move them, their carriages broke under the concentrated weight, and they consumed mountains of munitions. The lombard, which apparently originated in Lombardy, and the basilisk had the same disadvantages. The fabled basilisk was a serpent whose very look was fatal. Its namesake in bronze was tremendously heavy, with walls up to 4 calibers thick and a bore up to 30 calibers long. It was seldom used by the Europeans, but the Turkish General Mustafa had a pair of basilisks at the siege of Malta, in 1565, that fired 150- and 200-pound balls. The 200-pounder gun broke loose as it was being transferred to a homeward bound galley and sank permanently to the bottom of the sea. Its mate was left on the island, where it became an object of great curiosity.

The third class of ordnance included the guns firing stone projectiles, such as the pedrero (or perrier, petrary, cannon petro, etc.), the mortars, and the old bombards like Edinburgh Castle's famous Mons Meg. Bars of wrought iron were welded together to form Meg's tube, and iron rings were clamped around the outside of the piece. In spite of many accidents, this coopering technique persisted through the fifteenth century. Mons Meg was made in two sections that screwed together, forming a piece 13 feet long and 5 tons in weight.

Pedreros (fig. 23c) were comparatively light. The foundryman used only half the metal he would put into a culverin, for the stone projectile weighed only a third as much as an iron ball of the same size, and the bore walls could therefore be comparatively thin. They were made in calibers up to 50-pounders. There was a chamber for the powder charge and little danger of the gun's bursting, unless a foolhardy fellow loaded it with an iron ball. The wall thicknesses of this gun are shown in Figure 24, where the inner circle represents the diameter of the chamber, the next arc the bore caliber, and the outer lines the respective diameters at chase, trunnions, and vent.

gun diameters
FIGURE 24—HOW MUCH METAL WAS IN EARLY GUNS? The charts compare the wall diameters of sixteenth-seventeenth century types. The center circle represents the bore, while the three outer arcs show the relative thickness of the bore wall at (1) the smallest diameter of the chase, (2) at the trunnions, and (3) at the vent. The small arc inside the bore indicates the powder chamber found in the pedrero and mortar.

Mortars (fig. 23d) were excellent for "putting great fear and terror in the souls of the besieged." Every night the mortars would play upon the town: "it keeps them in constant turmoil, due to the thought that some ball will fall upon their house." Mortars were designed like pedreros, except much shorter. The convenient way to charge them was with saquillos (small bags) of powder. "They require," said Collado, "a larger mouthful than any other pieces."

Just as children range from slight to stocky in the same family, there are light, medium, or heavy guns—all bearing the same family name. The difference lies in how the piece was "fortified"; that is, how thick the founder cast the bore walls. The English language has inelegantly descriptive terms for the three degrees of "fortification": (1) bastard, (2) legitimate, and (3) double-fortified. The thicker-walled guns used more powder. Spanish double-fortified culverins were charged with the full weight of the ball in powder; four-fifths that amount went into the legitimate, and only two-thirds for the bastard culverin. In a short culverin (say, 24 calibers long instead of 30), the gunner used 24/30 of a standard charge.

The yardstick for fortifying a gun was its caliber. In a legitimate culverin of 6-inch caliber, for instance, the bore wall at the vent might be one caliber (16/16 of the bore diameter) or 6 inches thick; at the trunnions it would be 10/16 or 4-1/8 inches, and at the smallest diameter of the chase, 7/16 or 2-5/8 inches. This table compares the three degrees of fortification used in Spanish culverins:

 
Wall thickness in 8ths of caliber
Vent Trunnion Chase
Bastard culverin 7 5 3
Legitimate culverin 8 5-1/2 3-1/2
Double-fortified culverin 6-1/2 9 4

As with culverins, so with cannon. This is Collado's table showing the fortification for Spanish cannon:

 
Wall thickness in 8ths of caliber
Vent Trunnion Chase
Cañon sencillo (light cannon) 6 4-1/2 2-1/2
Cañon común (common cannon) 5 7 3-1/2
Canon reforzado (reinforced cannon) 5-1/2 8 3-1/2

Since cast iron was weaker than bronze, the walls of cast-iron pieces were even thicker than the culverins. Spanish iron guns were founded with 300 pounds of metal for each pound of the ball, and in lengths from 18 to 20 calibers. English, Irish, and Swedish iron guns of the period, Collado noted, had slightly more metal in them than even the Spaniards recommended.

chambered cannon
FIGURE 25—SIXTEENTH CENTURY CHAMBERED CANNON. a—"Bell-chambered" demicannon. b—Chambered demicannon.

Another way the designers tried to gain strength without loading the gun with metal was by using a powder chamber. A chambered cannon (fig. 25b) might be fortified like either the light or the common cannon, but it would have a cylindrical chamber about two-thirds of a caliber in diameter and four calibers long. It was not always easy, however, to get the powder into the chamber. Collado reported that many a good artillerist dumped the powder almost in the middle of the gun. When his ladle hit the mouth of the chamber, he thought he was at the bottom of the bore! The cylindrical chamber was somewhat improved by a cone-shaped taper, which the Spaniards called encampanado or "bell-chambered." A cañon encampanado (fig. 25a) was a good long-range gun, strong, yet light. But it was hard to cut a ladle for the long, tapered chamber.

Of all these guns, the reinforced cannon, was one of the best. Since it had almost as much metal as a culverin, it lacked the defects of the chambered pieces. A 60-pounder reinforced cannon fired a convenient 55-pound ball, was easy to move, load, and clean, and held up well under any kind of service. It cooled quickly. Either cannon powder or fine powder (up to two-thirds the ball's weight) could be used in it. Reinforced cannon were an important factor in any enterprise, as King Philip's famed "Twelve Apostles" proved during the Flanders wars.
Fortification of sixteenth and seventeenth century guns
Spanish guns Thickness of bore wall
in 8ths of the caliber
English guns
Vent Trunnions Chase
Light cannon; bell-chambered cannon 6 4-1/2 2-1/2 Bastard cannon.
Demicannon 6 5 3
 
Common cannon; common siege cannon 7 5 3-1/2
 
Light culverin; common battering cannon 7 5 3 Bastard culverin; legitimate cannon.
Common culverin; reinforced cannon 8 5-1/2 3-1/2 Legitimate culverin; double-fortified cannon.
Legitimate culverin 9 6-1/2 4 Double-fortified culverin.
Cast-iron cannon 10 8 5
 
Pasavolante 11-1/2 8-1/2 5-1/2
 

While there was little real progress in mobility until the days of Gustavus Adolphus, the wheeled artillery carriage seems to have been invented by the Venetians in the fifteenth century. The essential parts of the design were early established: two large, heavy cheeks or side pieces set on an axle and connected by transoms. The gun was cradled between the cheeks, the rear ends of which formed a "trail" for stabilizing and maneuvering the piece.

Wheels were perhaps the greatest problem. As early as the 1500's carpenters and wheelwrights were debating whether dished wheels were best. "They say," reported Collado, "that the [dished] wheel will never twist when the artillery is on the march. Others say that a wheel with spokes angled beyond the cask cannot carry the weight of the piece without twisting the spoke, so the wheel does not last long. I am of the same opinion, for it is certain that a perpendicular wheel will suffer more weight than the other. The defect of twisting under the pieces when on the march will be remedied by making the cart a little wider than usual." However, advocates of the dished wheel finally won.


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