Privateers were fast, and had large crews, but they too were lightly built, intended to prey on the defenseless. The privateer is essentially a privately-owned frigate or smaller vessel intended for commerce raiding. They could be fairly formidable; the Red Dragon (1595), for example, had 38 guns (2 demi-cannon, 16 culverins, 12 demi-culverins, and 8 sakers). (Wikipedia/Red Dragon).
The "East Indiamen" had an unusually large number of guns for a merchantman, and a large crew, but the guns were still usually of relatively light caliber. They also tended to have stouter hulls. The Dutch called them retourschepen (return ships). An example is the ill-fated Batavia (1628): 160 feet long, 1200 ton displacement, six-inch oak hull, and 30 guns. (Dash 72). However, I don't know the calibers. The Hollandia (1742) and Amsterdam (1748) had 8x12pdr, 16x8pdr, 8x4pdr, and 10 swivel guns. (ageofsail.net). The Bonhomme Richard (1765) was unusually powerful; 6x18pdr, 28x12pdr, 8x9pdr. Another exception was the Prins Willem (1652); 4x 24pdr, 10x12pdr, 22x18pdr, 6x8pdr. However, it is possible that some of these more powerful East Indiamen were built with the intent of long-term leasing to the navy. (Glete 55).
Guns
Heavy weapons are the sina qua non of the warship, and as of RoF, the only heavy ship-to-ship weapons were cannon. By long practice, naval cannon are called guns. The term guns carries the further implication that the weapon is intended for low angle fire; "mortars" are designed for high angle fire, and howitzers occupy an intermediate position. Here we are interested mostly in guns, but of course AA guns require freedom of elevation.
The smallest fixed weapons, the swivel guns, were used against enemy personnel or small boats and fired half-pound iron round shot. (Elkins 42). They weren't counted as "guns" for the purpose of comparing warships because they weren't mounted on carriages.
Until 1715, English guns were classified according to their caliber (bore diameter). Later, guns were specified by the weight of the shot they fired. Lengths can vary so guns are customarily identified by both weight of shot and length, e.g., an 10-foot long gun firing 24 pound shot is a "24–10."
Please note that the shot weights were nominal; in the early-nineteenth century, a "24 pounder" had a true caliber ranging from 5.8230 inches (English) to 6.1107 inches (Swedish). If the windage (see below) were the same (1.5 French "lines", 0.13324 English inches), that would mean that it fired shot weighing anywhere from 25.906 pounds (English guns) to 30.1048 (Swedish); with the French (28.7511) near the maximum. (Simmons 63).
I believe that mortars continued to be classified by their caliber, and this was carried over to shell-guns in the mid-nineteenth century. Thus, the US Navy had both the 8-inch shell gun and a 64-pounder with an 8 inch bore. (Dahlgren 24).
Cannon may have unusually long barrels to (hopefully) give them extended range. Such a long gun might be used as bow or stern armament, and the privateer's "long tom" was a shifting broadside gun. But this wasn't common because most ship-to-ship actions were fought at close range.
Guns were sometimes shortened to save weight, to trade weight for the ability to fire heavier shot, or some combination of the two (as in the famous carronade, for which gun weight was 50–75 times the shot weight). The cannonade, a short-barreled (hence, short range but light) cannon throwing a heavy weight of metal for its size, was introduced into the British navy in 1779. (Chapelle HASS 56). By 1815, carronades had become the main armament on small ships. (Glete 30). It has already appeared in canon; the USE ironclads mount them as secondary weapons. (Flint and Weber, 1632: The Baltic War, Chap. 38.)
By way of explaining the carronade's popularity, consider that a Napoleonic 5.17-foot carronade firing 42 pound shot (equivalent to the heaviest gun on a Napoleonic battleship) weighed 22.25 hundredweights (cwt.; each 112 pounds); a long gun of the same weight would be just a 9–7 (23 cwt) or a 6–8.5 (22 cwt). There was even a 68-5.17 carronade weighing 36 cwt; it could replace a long 12-9.5 (36 cwt) or 18-9 (39 cwt). (Ireland 47-9). A carronade-based warship could throw an incredible weight of metal at an enemy-if that enemy came within range. Chappelle says that carronades were an excellent choice for a fast ship, but a poor one for a sluggard (152).
After the War of 1812, there was a movement to simplify the ammunition logistics by having, e.g., all guns on a battleship use 32-pound shot, but varying gun barrel length, so that there were "heavy 32s" on the lower deck, "medium 32s" on the gun deck, and "light 32s" on the spar deck. (Glete 30; ChapelleHASN 318). At least, that was the ideal; in practice there was great temptation to boost fighting ability by putting 42-pounders on lower and spar decks (the latter as 42-pounder carronades), and relegating medium 32-pounders to the upper deck.
Table 1–2 presents a composite overview of seventeenth-century naval artillery; please note the variation in bore diameter, shot weight, barrel length, and gun weight. Guns could be specified as thicker ("reinforced," "double"), thinner ("bastard"), shorter ("cutt"), and with a tapered bore ("drake"). There were also variations between gun-founders, and even from gun to gun. ("Demi cannon could. vary up to three hundred weight within the same batch.:-Bull 8).
The largest seventeenth-century naval artillery were 42-pounders (British navy) or 36-pounders (most others). The former was first used in large numbers on Sovereign of the Sea (1637) and thereafter was mostly used on First Rates. The demi-cannon (32-pounder) was the main battleship gun after 1745. (Nelson).
The diameter of the bore fixes the volume and thus the mass of the projectile if it's spherical, and determines the proportionality of volume to length if it isn't. These in term affect the aerodynamic characteristics of the projectile. The diameter also strongly affects how much damage the projectile does for a given impact velocity.
Shot diameter must of course be at least slightly less than the bore diameter; for a cast iron (density 0.2682 lb/in3) cannonball, the diameter (inches) is 1.937 * cube root of the weight (pounds). (Collins/Cannonballs)
Gun and projectile size grew only gradually over the next two centuries. The 32-pdr was a popular ACW carriage gun, weighing 27–57 cwt, and firing either 32.5 pound shot or a 26 pound shell with 0.9 pounds powder. The most powerful gun actually mounted on a ship in the ACW was a 15-inch Dahlgren, weighing 42,000 pounds. It had an 8 -14 man crew and fired 440 pound solid shot or a 330 pound shell containing 13 pounds powder. Charges were 50 and 35 pounds, respectively. (Symonds 36; Heidler 548; Canfield).
Manufacturing tolerances for both cannons and cannon balls were loose, so, to ensure that most balls would fit into the guns for which they were intended, the bores were deliberately made to a diameter greater than the intended shot diameter. The resulting gap, measured as either a difference in diameter or as an annular area, was called "windage." That word has at least three other meanings in ballistics so I will speak of the looseness of fit as "bore-windage." In our period, the bore-windage wasn't standardized, but was typically 0.25 inches. In 1716, the British adopted the rule that the bore diameter should be 21/20th the shot diameter; a 24-pound shot had a shot diameter of 5.547 inches, windage of 0.277 inches, and was fired from a gun of 5.823 inches caliber (Douglas 71). In 1787 this was changed to 25/24th for the Blomefield pattern guns. The short-barreled carronades could be bored more accurately; bore diameter was 35/34ths shot diameter. The French, in contrast, allowed just 0.133 inches (1/45th caliber for a 24 pounder) for heavy (18+) guns and 0.088 inches for field guns. (74).
It should perhaps be noted that even if shot and bore were a perfect fit initially, they wouldn't necessarily stay that way. The shot would rust; the bore would be fouled. Both were subject to expansion when heated, which I would think would especially be a problem for the gun if it had been fired repeatedly. Douglas (74) suggested that at white heat 24-pound shot expanded by 1/70th diameter, and smaller shots by less.
Guns may also be classified according to their construction, as muzzle or breech loading, and as smoothbore or rifled.
Muzzle versus Breech Loading
The cannon barrel is a tube, open at one end (muzzle) and h
opefully closed at the other (breech). To load a muzzle loader, it is drawn in, the bore is cleaned, the powder charge and the shot are rammed in at the muzzle end, and the cannon is run back out the gun port. A breech loader has a loading door at the breech end; this is opened, the charge and shot are inserted, and the door is closed.
A breechloader could have either an integral chamber, into which the powder and shot were placed directly, or a removable chamber (Buchanan 251ff); this would be loaded with the powder and shot and then the chamber placed in the breech. The removable chamber looked somewhat like a beer mug.
The proponents of muzzle loading and breech loading have engaged in a half-millennium long struggle for ascendancy. Just because modern naval guns are breech loading doesn't mean that this was a foregone conclusion, or that the vagaries of technological and economic development in the new time line might not provide a niche for muzzle loaders.
The first naval cannon were breech loaders, and Mary Rose (1545) carried both wrought iron breech loaders and bronze muzzle loaders. By the early-seventeenth century, the main guns of a warship were all muzzle loaders, but her swivel guns were still breechloaders.
Muzzle loaders usually were brought inboard for loading. According to Martin and Parker (193), this was done manually; "the much more efficient process of allowing a gun's own recoil to bring it inboard under the restraint of a breeching rope was not developed until well into the seventeenth century." Smith, Seaman's Grammar (1627) says, "britchings are the ropes by which you lash your Ordnance fast to the Ships side"; in the light of Martin's comment, these lashings were too tight for recoil-aided loading.
The longer the barrel, the less convenient it was to load it from the muzzle end, and high-caliber guns tended to have long barrels. With black powder, there wasn't much advantage to making barrels longer than 10 feet, because the powder burns quickly, but with cordite the lengthening of the gun barrels permitted an increase in muzzle velocity. (Sweet 171).
On the Mary Rose, the gun crews were so cramped that it's been suggested that they engaged in outboard loading; the gunner would sit on the barrel, sticking out the gunport, to reload the piece (Konstam 40). A Dutch painting shows this was still going on in 1602. (Gould 227).
While short-barreled carronades were easy to load, they had other problems; the flash could set fire to the rigging, and the vent fire could do the same to the hammocks. (Douglas 103).
For any smoothbore muzzle loader, the shot had to fit loosely in the bore, so it could be rammed down. But when fired, gas could escape around the shot and out the muzzle, and it was also difficult to keep the projectile centered as it moved down bore.
Late in the history of muzzle loading artillery, the gas escape problem was reduced by use of a gas check, a thin disk that filled the cross-section of the bore. The first gas check was a papier mache disk inserted between the cartridge and the base of the shot, but by 1878 a copper disk was attached to the base of the projectile. (Ruffert). The centering problem theoretically could have been addressed with a sabot (see part 3), but that wasn't normally done.
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The most obvious advantage of the breech loading system was that the gun could be reloaded from inboard while run out, which potentially increased the rate of fire.
The most enduring design problem with breechloaders, which had a door rather than solid metal at the breech end, was preventing gas loss at the breech. The more powerful the gun, and the greater the strength of the powder, the greater the pressure that this mechanism had to withstand.
In Elizabethan breechloaders, the removable chamber was wedged into the breech. Lucar (1588) warns that the gunner "ought not stand upon that side of the piece where the wedge of iron is placed. because [it] may through the discharge of the piece fly out and kill the gunner." (Corbett 333).
According to EB11/Ordnance, the first successful breech mechanism was that invented by Armstrong (1854). The vent piece (a vertically sliding block) was secured by pressure from a hollow screw. To load, this was loosened, the vent piece removed, and the projectile and charge inserted through the hollow. The vent piece was then replaced and the screw tightened. On the chamber side the vent piece had a coned copper ring that fitted into a coned seating.
Unfortunately, the success was limited. "During the bombardment of Kagoshima in 1863 there were 28 accidents in the 365 rounds fired from 21 guns. On a number of occasions the vent pieces were blown from the guns. The guns were also inaccurate." (Brassington).
Moreover, the rise of the ironclads demanded an increase in punch, and the imperfect seals of the mid-nineteenth-century breechloaders frustrated this. The British navy conducted comparative trials and in 1865 it decided to switch to rifled muzzleloaders! (Hogg 16).
This turnabout didn't last long. In 1879, one of the guns of the HMS Thunderer misfired; the misfire was undetected and the gun was reloaded, making it inadvertently double-shotted. When the gun fired again, it exploded, killing everyone in the turret. This accident couldn't have happened with a breechloader-the gun crew would have seen the unexploded charge when it opened the breech-and the British navy reluctantly abandoned muzzle-loading for good (Batchelor 11). At least for new construction; there were still battleships with big muzzle loaders in active service in 1894 (Clowes 47).
This accident provided the impetus for change, but there were other considerations at work. A new powder that could achieve a higher muzzle velocity had been developed. But if it was used in a muzzle loader, the shell zipped out before the charge was exhausted. In other words, the barrels weren't long enough. But if the barrels were lengthened, then recoil wasn't sufficient to bring the muzzle inside the turret for loading. This was actually done on HMS Inflexible (1876) (Watts 56); the muzzle was lowered to an armored loading hatch and the shell inserted by a hydraulic rammer.
EB11/Ordnance describes several breech mechanisms based on the interrupted screw principle. Normally the threads of a screw engage continuously with those of a threaded screw box. The problem with a continuous screw breech plug is that it can be time-consuming to tighten and untighten. A 16-inch naval gun might develop a gas pressure of 40,000 psi, necessitating a 1,400 pound plug. (NAVORD).
The basic interrupted screw concept was invented much earlier than you might think. In a musket manufactured at Mayence around 1690, "the muzzle portion turns round one-sixth of a circle, and then pulls out a short distance, liberating the breech-piece, which can be thrown back on a hinge." (Horton 302).
With an interrupted screw, the threads of both are discontinuous, so that there is a screw orientation such that it can be slid into the screw box without engaging. For example, looking down the axis of the box, it might have threading from 12 o'clock to 3 o'clock, and 6 to 9. If so, then the screw in the slide-in orientation would have threading only from 3 to 6 and 9 to 12. Once inserted, such a screw would be given a quarter-turn, and then the threads would be fully engaged. (Wilson 249).
The disadvantage of the classic interrupted screw was that it engaged only along half the circumference and thus, to have the same sealing strength as the continuous screw, would need to be twice as long.
This disadvantage was largely overcome by the Welin stepped interrupted thread. The circumference of the screw is divided into several (2–4) groups. Each group can further be divided circumferentially into several arcs, which progressively increase in diameter, creating a stepped pattern. On the screw, the arcs at the lowest step level are blank, and the other arcs are threaded.
In the disengaged position, a threaded arc on the screw can face a threaded arc on the screw box, provided that the arc on the box is deeper so they don't engage. You slide the screw in and then turn it to engage. With three different threaded diameters, and one smooth, you have threaded engagement for 75 % of the circumference, and with two groups, a one-eighth turn is need to engage. Actually cutting a Welin screw must have been a complete bear.
In canon, there are post-RoF-manufactured breech-loading rifles as of 1634 (1634:TB
W Chap. 27), although in very limited quantity (Chap. 5), but the Americans, in building their first ironclads, deliberately opted for muzzle loaded naval guns because of unspecified resource limitations. (Flint, Weber, 1633, Chap. 4).
Smoothbore versus Rifled
The cannon in use as of the RoF have smoothbore barrels, which means just what it says.
However, the barrel of a firearm may be rifled-given helical grooves-in order to impart a spin to a projectile. The effect would be to gyroscopically stabilize the flight of the projectile.
Rifling was introduced into small arms in the sixteenth century, as we know from a 1563 Swiss ordinance: "For the last few years the art of cutting grooves in the chambers of the guns has been introduced with the object of increasing the accuracy of fire; the disadvantage resulting therefrom to the common marksman has sown discord amongst them. In ordinary shooting matches marksmen are therefore forbidden under a penalty of L10 to provide themselves with rifled arms. Every one is nevertheless permitted to rifle his military weapon and to compete with marksmen armed with similar weapons for special prizes." (Chamber's Encyclopaedia 718). These rifles, apparently, were used to fire balls, since elongated projectiles reportedly were not invented until 1662.
The first rifled artillery pieces were probably those of Cavalli (1846) (Quartstein 45). Both rifles and smoothbores were used in several mid-nineteenth-century naval conflicts, notably the American Civil War, the Second Scheswig War, the Third Italian Independence War, and the Guano War.
Rifling was not a panacea; reloading was more difficult, and range and accuracy were not always improved (the projectiles tumbled if they weren't loaded properly). The metal ("lands") between the grooves can get worn down. Also, during the American Civil War, rifled artillery seemed more prone to burst than muzzle-loading Dahlgrens, and rifled projectiles couldn't gain range by ricochet. (Manucy 17; Jenkins; Schneller). This may explain the Union navy's wartime preference for smoothbores (Heidler 1046), even though in 1859, after comparative testing, the US government had concluded "the era of smoothbore artillery has passed away." (Bell 44).
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