This article is concerned with naval artillery—swivel guns and up—not with the small arms that might be carried onboard. It looks at both what was in use at the time of the Ring of Fire (RoF; 1631), and what up-time innovations might be introduced post-RoF. Much of what is discussed here is relevant to land warfare, too.
Before I go into details, I want to issue a few warnings. First, avoid the "Hornblower Syndrome." By that I mean, don't assume that naval practices that were de rigeur during the Napoleonic Wars were equally commonplace two centuries earlier. It's okay to look at Napoleonic fleets for inspiration, however.
Secondly, recognize that in this article, I cover technological improvements that, in the old time line, spanned several centuries and individually may have taken years to develop (and decades to gain acceptance). The fact that I mention a possible technology should not be construed as meaning that Admiral Simpson will be implementing it next year. Or even next decade.
Third, consider armament development as a gestalt. The value of one technology may depend on the availability of another. Coordinated, albeit modest advances, may accomplish more than a narrowly focused breakthrough.
Early Modern Warship Classification
Warships serve a variety of functions, including participation as combatants or reconnaissance elements in fleets, escorting friendly shipping, raiding or blockading enemy shipping, and bombardment of enemy forts and towns. One size does not suit all purposes, so a navy will have a variety of warships, with armaments ranging from heavy to light.
In 1612, British warships were divided according to tonnage into ship royal (800 –1200 tons), middling ships (600 –800), small ships (250 –600), and pinnaces (80 –250). (Miles 20). They were reclassified (for wage purposes) into six rates, according to crew size, in 1626: 1st (>300), 2nd (250 –300), 3rd (160 –200), 4th (100 –120), 5th (60 –70), and 6th (40 –50) (threedecks.org), and yes, I know there are gaps.
The 1621 naval budget divided Swedish warships into realskepp (regal ship), örlogsskepp (warship), mindre (small) örlogsskepp, pinasser (pinnaces), and farkoster. This scheme was abandoned after 1622. On Oct. 6, 1633, Axel Oxenstierna proposed a new system that divided örlogsskepp into stora (large) and rätta (normal), and split off minsta (smallest) from mindre. A simplified version of this system was used in the 1640s through 1670s. (Glete 328ff).
Naval expansion in the second half of the seventeenth century resulted in the development of rating systems based on the number of guns: six rates in England, seven charters in the Dutch Republic, and five ranges (and frégates légerès as a sixth) in France. (Glete). Here's one tabulation:
Table 1- 1: Comparative Warship Classification
Number of Guns
( threedecks.org; cp. Ireland 42ff O'Neill 57; Harbron xiv, 24)
I have included several later British rating schemes; you can see how Napoleonic ships-of-the-line were expected to carry more guns than their seventeenth-century counterparts. Just to complicate matters further, the British rates were sometimes subdivided into classes.
In counting guns, the British navy ignored swivel guns and, in the nineteenth century, initially ignored carronades. Note that the rating system only considered the number of the guns, and not the weight of the shot they threw.
The term "battleship" dates back only to 1794; it was an abbreviation of "line-of-battle ship." I will unabashedly use the term "battleship" anachronistically to refer to the more powerful fleet units of any time period.
Initially, ships of the first four rates were considered powerful enough to be placed in the "line of battle," which didn't exist as a battle formation until the mid-seventeenth century. But by the mid-eighteenth century fourth rates tended be used only in backwaters (or by inferior navies). The principal battleship was the third rate, especially the Napoleonic "74." First and second rates were either flagships, or relegated to home defense.
In the 1630s, the term frigate still had strong traces of its original meaning, a kind of war-galley. It had come to mean a sailing ship that had long, sharp lines like those of a war-galley (fragata); they were sometimes called "galleon frigates" to differentiate them from the "galley frigate." In English usage, these race-built sailing ships could be merchantmen or warships.
The only "frigates" on the 1633 Navy List had a mere three guns and were probably royal yachts. Pepys considered the first true frigate built in England to be the Constant Warwick (1646), modeled on a French privateer; bearing 26 –32 guns (Naval Encyclopedia). By 1650, the term was fixed as meaning a warship (OED), and it came to mean one with two decks, only one of which was a gun deck. Frigates were of the fifth and sometimes the sixth rates (a sixth rate with only a single deck was a "post ship" or a "corvette").
Frigates were used by fleets for reconnaissance; by convention, in a fleet engagement, a battleship wouldn't fire on a frigate unless the frigate had fired first. (And then the battleship would probably blow it out of the water.) They were also the ship of choice for detached service, much like late-nineteenth-century cruisers or twentieth-century destroyers.
A large and diverse group of British warships weren't rated. These included sloops-of-war, bomb ketches, and purpose-built fireships. In 1805, the sloops could further be divided into ship-rigged (three masts), with or without a quarterdeck, and brig-rigged (two masts). These all typically had 14 –18 guns. (Miller 27). It's worth noting that in the mid-nineteenth-century American navy, a sloop-of-war could be a quite powerful warship. USS Portsmouth (1843) had 18x32pdr and two Paixhans (64pdr shell guns).
Merchant ships carry armament only when necessary. In the seventeenth-century southern Baltic, where piracy is rare, they typically are unarmed. In dangerous waters such as the Caribbean, the Mediterranean, and certain Asian regions, they either must have cannon or be accompanied by armed escorts.
The cheapness of cast iron guns made it possible to increase the armament of the merchant ship. (Glete 52). While specialized warships existed even in the sixteenth century, most powers then didn't maintain permanent navies of significant size. Hence, they had to hire armed merchantmen. And to make sure that the civilian shipyards built ships that would be of value in wartime, the state gave economic incentives, such as reduced custom duties. (53).
Nonetheless, the specialized warship of the seventeenth century not only carried more guns, but often heavier ones. An armed merchantman might carry twelve-pounders, but 24-pounders and up were "exclusively warship armament." (Glete 28).
Because of the flimsiness of their hulls, the armed merchantmen couldn't slug it out for very long. Moreover, their crews were too small for sustained fire. If the guns were already loaded, then with one man per gun, they could get off one broadside quickly. And if both sides had been preloaded, and the ship turned, it could get off a second broadside the same way. After that, sustained fire was limited to a few guns. (Glete 53). They were slow, too.
Nonetheless, in the 1630s, an armed trader could be loaned, voluntarily or otherwise, to the Crown for emergency use in the fleet. But by the mid-seventeenth century, their military use was usually as convoy escorts, not as fleet units. (Glete 170). The Swedes were supposedly the last to use hired armed merchants in the main battle fleet. (Glete 193). However, the concept reappeared in the form of the early-twentieth-century Imperial Russian Volunteer Fleet, government-subsidized merchant ships built to an enhanced standard with a view toward wartime conversion. (Ireland 1997, 28).
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).
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).
Table 1-2: Guns Used in Early 17th Century British Navy
9.5 or 10
(Lavery 97ff; Manganiello 26: Peterson 14; Glete 27; Grundner 127; Corbett 321ff; Collins). Costs are estimates for new ordnance from Royal Ordnance Inventory for the Army. Crew size L A Army from Manganiello, N Navy from Pepys 1677 (Lloyd 81).
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 hopefully 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 mâché 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.
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:TBW 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).
Even so, there were skeptics. After the Battle of Lissa (1866, Austria vs. Italy), Tegethoff, the Austrian commander, commented, "the lack of results on the part of the enemy have shown that smoothbore guns on the sea have much more value than a rifled one, since a rifle requires for best results at long range a still position, difficult to find on the sea." (Greene 254).
The driving force for the adoption of rifled guns appears to have been not so much increasing effective range but that they could fire an elongated shell, thus one carrying more explosive for a given caliber. (Colomb 340ff). But it took perhaps two decades to perfect heavy rifled cannon (Bell 44; Lewis 65), and Dahlgren smoothbore-armed Civil War vintage monitors were placed on coastal defense duty during the Spanish-American War.
In order to apply spin to the projectile, it must somehow engage the rifling. With small arms, the bullet could be made of lead, which is malleable. There were two problems with making artillery projectiles out of lead. The first was that lead was expensive, and the second was that lead, being soft, would foul the inside of the barrel.
A number of expedients were tested in the nineteenth century. A lead coating on the projectile was introduced by Baron Warhendorff in the 1840s. (Kinard 222). That wouldn't be as expensive as making the whole thing out of lead, but fouling would still be a problem. The British nonetheless used this system with breech loaders.
Whitworth and Lancaster made projectiles with twisted side faces to match a twisted bore, hexagonal for Whitworth, oval for Lancaster. When mass produced, the rounds tended to jam in the bore. The Confederates used some Whitworth rifles.
For rifled muzzle loaders, one had to provide sufficient windage that the projectile could still be rammed down the barrel. One solution (Armstrong, 1854) was to provide the projectiles with studs to engage the grooves of the rifling. The engagement is reliable but the projectile must be studded to match the twist in a particular gun, and the gun cannot have increasing twist. Also, the grooves must be wide and deep to accommodate the studs, and that weakens the gun, whereas the studs increase air resistance to the projectile. (Bruff 303).
If the studs were taller than the depth of the grooves, there would be a clearance between the main body of the projectile and the lands (the uncut portions of the bore between the grooves). (Woolwich 182). Unfortunately, if the studs have clearance, and there's no gas check, then gas escapes and damages the bore.
It was discovered that the copper gas check I mentioned earlier not only reduced the gas loss from windage, it also engaged the rifling. It was used in rifled muzzle loaders, but it was found advantageous to make the grooves shallower and more numerous than in a breech loader.
However, the most successful ploy was to place "a copper 'driving band' into a groove cut around the body of the projectile." (EB11/Ammunition). While the basic concept is in Grantville Literature, there are some serious engineering considerations. We have to figure out what material to make it out of, how thick and long it should be, whether to have one long band or several short ones, where on the projectile body to place it, and how to secure it there. The choices we make, in turn, determine how well it engages the rifling, how much wear it imposes on the bore, and the aerodynamic characteristics of the projectile. (See 1922 EB/ "Ammunition").
In canon, each of the USE ironclads is equipped with four 10"x 12 rifled muzzleloaders and six rifled 8" x 4 carronades. The ten-inchers fire studded shells. (1633 Chap. 4; 1634: TBW Chap. 38)
Smoothbores may be converted into rifles by insertion of a wrought iron tube (reducing the caliber, probably by about two inches) after reaming out the old bore to match the outer dimension of the tube.
With spherical shot, you impart spin by creating friction between the ball and barrel, either by stuffing a patch between the two, or giving the ball a coating of lead or other soft metal. The patch, typically cloth or leather, is placed on the mouth of the rifle and the ball is placed over it. The ball is then stuffed down. Besides promoting spin by filling the grooves, the patch helped prevent the ball from riding back upbore before firing, thus separating bullet and powder, and avoids transfer of lead from ball to barrel. (Fadala 94ff).
There will no doubt be heated arguments with regard to the fine points of rifling: the number of grooves, the degree of twist, and the shape of the groove.
Rifling does increase the friction between the projectile and the barrel, and this can reduce muzzle velocity and also generate heat and quicken the erosion of the barrel. This has led to proposal of hybrid guns, with either a smoothbore breech and a rifled muzzle (Alsop, US Patent 37193) or the reverse (A'Costa 4660312; Amspacker H1365). However, a more conventional solution to unacceptable friction has been to put the projectile into a plastic-sabot (see part 4) so that the friction is plastic-metal rather than metal-metal.
Wrought iron. Until the sixteenth century, cannon were forged; the tubes were built up from longitudinal metal strips, and these were held together by metal hoops. (This was blacksmith work, and blacksmith Marthinus Ras made three muzzle loading 6.5 pounder cannon by this ancient method during the Boer War.)
The hooped bombard of the fourteenth century was made of wrought iron. But by mid-sixteenth century, the large wrought iron pieces were only found on small merchant ships and in peripheral fortifications. Small wrought iron swivel guns may still exist in our period.
Bronze first appeared in hooped bombards in the early-fifteenth century. In the sixteenth century, it was the dominant gun metal. I should note that the British navy has the incredibly annoying habit of identifying bronze guns as "brass." Brass is a copper-zinc alloy, bronze is copper-tin; in the sixteenth century, the preferred ratio was 90-10. (Guilmartin 307). While tough, bronze is soft and thus subject to abrasion, especially if the barrel is hot from repeated firing. Bronze also suffered from a lack of homogeneity. When cooling, the tin has a tendency to separate from the copper, causing white blotches called "tin spots" which are eaten away by the powder gas. (Ord1880,76ff).
There were essentially four kinds of bronze guns: pedreros, cannons, culverins and mortars. Pedreros are stone-throwers and because of the relatively low density of stone, they typically were of large caliber (12 –50 pounders for sea service, up to 1000 pounders for land sieges), with short barrels (4 –8 times caliber ) and a reduced diameter (1/2 to 1/3 caliber) powder chamber. The Ottomans cast them muzzle down.
Both cannon and culverins fired cast iron cannonballs, but the culverins had long (18 –40 times caliber, mostly 25+) unchambered bores, whereas the cannon had shorter (15 –28 calibers, mostly 15 –20) bores; early cannon often had reduced diameter powder chambers. (Guilmartin 175ff; Meide; Hoskins 119ff).
Mortars were designed to shoot at high angle trajectories, and were mostly used as siege weapons. A ship could carry mortars that could be landed and used to strike a position that was out of reach (because of shoals or batteries) of the ship's guns. Mortars had lengths of 1.5 –3 calibers.
Cast iron is iron with more than 2% carbon. Depending on how the carbon is combined, it may be called white (hard but brittle) or grey (softer but tougher, preferred for cannon). Cast iron guns appeared around 1543. Over the course of the seventeenth century, cast iron gradually supplanted bronze as cannon material. This was despite bronze's advantages; it didn't rust, it was easier to cast ("iron had a tendency to harden before all of it could be poured into the mould"—Lavery 84), it could be recast without loss of strength, and bronze cannon could always be made lighter than cast iron guns of equal strength. For example, in 1742, a British navy 32-9.5 weighed 6048 pounds in bronze and 6384 in cast iron, and a 42-10 was 7392 pounds in bronze and a walloping 8400 in iron. (Meide).
Nineteenth-century cast iron had a lower yield and breaking strength than bronze (Ord1800, 189), so additional metal was used, preferably at the breech. (Hazlett 82). While a more uniform cast iron could be made in the early-nineteenth century, thanks to improvements in iron-making (coke replacing charcoal, steam replacing water power)(Morriss 188-9), it remained unpredictably brittle (light field pieces were especially prone to bursting—Hazlett 220), thanks presumably to variations in the nonferrous constituents (phosphorus, sulfur, etc.). In the Civil War era, Rodman wrote, "we are at present far from possessing a praactical knowledge of the properties of cast iron in its application to gunfounding." (Wertime 164) and Cooke (53) made a similar complaint in 1880.
Unfortunately, bronze cannon were much more expensive—initially three- or four-fold; eight-fold by the 1670s (Unger 149; Lavery 84). This was the result of a decrease in the price of cast iron; bronze prices were stable. Consequently, bronze guns sometimes remained in service for more than a century—Rodger 215. (But even iron guns were very expensive and were kept in active service as long as possible—Glete 77.) Wrought iron reappeared as a reinforcing element in the mid-nineteenth century; in 1880 it was 2–3 times as expensive as cast iron. (Cooke 654).
As time passed, first the lighter guns were made from cast iron, then all guns save those on "prestige" ships (flagships and royal yachts) went ferrous. (Glete 24ff). The 42-pounder was first cast in iron in 1657, but 30% of culverins were still bronze in 1660 (Nelson).
Even on first class warships, bronze was pretty much no longer on deck by the 1770s. (Although the British navy still had some bronze mortars in the 1860s.) Bronze continued to be used as a gun metal for field artillery in the nineteenth century, as late as the Crimean War and American Civil War, no doubt because of its weight advantage. These included a 14-pounder James rifle. Unfortunately, it wasn't suitable for rifled weapons. Since bronze is softer than iron, and the rifling exposed more in tin spots, "repeated firings rapidly wore down the lands, thus making the pieces increasingly inaccurate." (Kinard 193; Hazlett 52). Even for smoothbores, the softness and the tin spots were problematic when challenged by the heavier projectiles and more powerful charges of the nineteenth century.
In the 1870s, the Italians and French found that guns cast from phosphor bronze (stronger, more homogeneous metal) were superior to those made using ordinary bronze, but concluded that the advantage was too small; the phosphorus had to be added in exact proportions and was "unstable." So-called "bronze steel," an ordinary bronze cast under pressure while chilling the interior, and subsequently forged cold, was also considered, but eclipsed by steel. (Ord1880, 77, 187).
Cast steel. Steel is potentially superior to cast iron, and to wrought iron and bronze, but it is quite difficult to cast without hidden defects (Kinard 230). Krupp cast his first steel cannon in 1847 (Krause 59). There was only limited use of cast steel rifled cannon (3" Sawyer) in the ACW.
By the l890s, ordinary steel was replaced by nickel steel. (Krooth 89).
Hollow casting. In the early-seventeenth century, muzzle-loading iron cannon were cast as single hollow blocks. Making the mold was tricky. In essence, there were two clay molds, a hollow one for the exterior and a solid one (core) for the interior. (Hall, 11ff; Fisher).
The hollow mold was built up over a pattern made of wood, rope, clay and a friable material like horse dung; the pattern defined the desired shape of the cannon interior. The pattern was coated with a release material, such as an ash-fat mixture or a wax, so the actual mold material wouldn't stick. This mold material was also clay-based, and might be reinforced with rope or animal hair. The mold was reinforced with metal straps, the pattern was carefully removed from its interior, and the mold was baked. The core mold of course was simpler to make.
The complete mold was lowered into a pit, muzzle up. Note that the interior (core) mold had to be held centered inside the larger mold by a metal spacer (cruzeta; chaplets), which would become part of the gun. In general, this didn't work out perfectly, the core would shift so the bore wouldn't be quite straight. (WeirML, 132).
The pit was filled with earth so as to hold the mold upright, a "feeding head" (riser) was attached, and the molten metal was poured into it. The latter had to have the right fluidity to properly fill the mold. Once the metal had cooled and solidified, the mold was broken so the casting could be removed. That meant that no two cannon could be identical.
The cannon was then finished off; the most important finishing steps were cutting off the riser, and reaming out the cast bore so that it had a smoother surface. Diego Prado y Tovar (1603) described a machine, possibly driven by animal power, for accomplishing this,. However, the drilling was vertical, with the cannon suspended and slowly lowered over the drill. Note that the machine was merely finishing a hollow casting. Indeed, hollow casting is plainly described in Mieth, A New Description of Artillery (Frankfurt 1684); chapter V discusses the cruzeta (Rainer Prem transl.). Bores were cast to the diameter of the shot and drilled out to the added diameter of the windage. (Hoskins 43).
Clay molds are criticized in 1634: TBW, Chapter 38: "Clay had a very low porosity, which meant that air bubbles in the molten iron were often unable to escape when the guns were cast and, instead, formed dangerous cavities and weak points in the finished guns." The gun barrels of the USE ironclads used in the Baltic War were fabricated by sandcasting. "Sand was far more porous, which made for much stronger, tougher artillery pieces." Historically, sand molds were introduced in Britain about 1750. (Lavery 84).
Another problem was intrinsic to the vertical casting method; since the bottom (breech) was under greater pressure than the top, and also better insulated, it would have been the last to solidify, and therefore tin would have migrated downward. The muzzles were thus only 3 –5% tin, resulting in brittleness, which was compensated for by flaring the muzzle.(Guilmartin).
There were other modest improvements over the eighteenth century. In Britain, these included providing full-size drawings to the gun founders (1716) and using copper rather than wood cores.
We may deduce the improvement in tolerances by examining the weight variation of the pieces. "In 1665, guns from a single batch of 9ft demi-cannon varied from 44 to 62cwt, those of 8.5 feet from 43 to 47, and culverins of 10ft varied from 40 to 46 cwt." (83). In contrast, the 32-pounders surveyed in 1803 –6 were 55 –57 cwt. (84).
Solid Casting. Over the period 1715 –45, Johann Maritz developed a new fabrication method. The cannon was cast solid, breech down, and then the bore was drilled out horizontally. The casting itself was much as in prior times, except that the core mold was no longer required. Boring itself, using an animal- or water-powered machine, took several days. (Kimpton). One curious aspect of the process is that it was the cannon that was rotated, the bit remaining stationary. (Alder 42). Solid casting was adopted in Britain in 1776 (Lavery 84).
Hot Blast. In the 1830s, American gunfounders attempted to cast iron by the more economical "hot blast" method, resulting in a disastrous loss of strength. At West Point foundry, 68.5% of those cast by cold blast (1826 –1834) were deemed "first class," compared to 4.02% of those produced (1835 –39) by hot blast. (Hazlett 36, 42).
Rodman Guns. These were hollow cast, with a trick; the core was itself hollow, in fact, two concentric tubes, and was cooled with pumped water while the molten iron was poured in around it. The metal would thus cool inside out, pre-stressing it in a desirable way. (Wikipedia/Rodman_Gun).
Built-Up Construction. The 1855 Griffen "Ordnance Rifle," a 10-pounder cannon with a 3 inch rifled bore, was built up by welding wrought iron bands together around a mandrel, boring, and rifling. (Kinard 192), or by building up a mandrel with welded iron rods and then winding several bars in spiral fashion about it (Hazlett 121). Note its similarities to the ancient bombard, in that it was "built up" from wrought iron! However, it is important to note that instead of forging the iron with a hammer—as was done with the 1844 "Peacemaker," which burst and killed two cabinet members—Griffen forged his iron rods in a rolling mill.
There was also the British Armstrong gun. This went through several permutations. In one, wrought iron bars were twisted into spirals and welded on their edges to form the barrel. (Tennent 106). In some cases the twisted coils were themselves shrunk onto an inner tube of mild steel. (Morgan xvi).
Wrought iron's advantage was that it was four times stronger than cast iron, and thus able to help resist the higher internal stresses (the result of the reduced windage) of a rifled gun. Saving manufacturing cost and time, Parrott shrunk a wrought iron reinforcing hoop onto the breech of a rifled barrel cast in the usual way. However, "large Parrott rifles had the worst record of any Union cannon for premature bursting . . . Of 110 large caliber Union cannon that cracked or burst in action during the war, 83 were Parrotts . . . ." After the first 1864 assault on Wilmington, Admiral Porter declared that the guns were "calculated to kill more of our men than those of the enemy." (Bell 8).
Around the end of the nineteenth century, the British and Japanese made use of wire wound construction. The "A" tube was wrapped multiple times with a high tensile strength wire and then the "B" tube was shrunk over this. (DiGiulian). The ten-inch guns of the new time line's USE Constitution are "wire-wound" (1634: TBW Chap. 38), presumably over a cast tube, but I don't know if a "B" tube was added.
In the early-twentieth century, heavy naval guns were built-up in hoop-over-tube fashion. The inner tube was placed breech end down in a cold pit, supported by a short mandrel. Heated hoops were placed one by one over the tube and cooled with a water spray, shrinking them onto the tube. (NAVORD. 136).
Spun Cast Monoblocs. In the 1920s, this was superseded by monobloc construction, made possible by the development of centrifugal spun casting. Despite the name, it typically involved concentric assembly of two or three tubes. Autofrettage was used to permanently deform the tubes in a desirable way. In autofrettage, the tube was pressurized hydraulically, just enough so that the outer limit was at its elastic limit, and then slowly relaxed. This increases the diameter of the bore and there is a permanent strain in the tube which varies from the inside diameter to the outside one.
It's likely that Grantville's machinists have heard of autofrettage. However, the autofrettage pressure must be much higher than the working pressure, which, for a cannon, is very high already. Autofrettage is typically used when pressures exceed 15,000 psi for brief periods of time, and so you must be able to achieve a higher pressure hydraulically.
Canon. In canon, the ironclad's main guns use Schedule 160 12" pipe as liners, wrapped with steel wire salvaged from the coal mine. (1633 Chap. 4). That, of course, is heavily dependent on twentieth-century materials. Should steel wire become unavailable, the backup plan is to cast bronze reinforcements around the tubes. I imagine that if there were no steel tubes, they would use cast iron.
A newly-cast gun barrel might have cracks and cavities (Hoskins 42). Before a gun was accepted (and paid for) by the military, it was tested. The British proofed guns by loading them with a double charge, and setting it off. The gun was then examined for cracks; this included filling it with water to see if it leaked. (Lavery 84). The gun would also be examined, usually visually, for the correctness of the bore diameter and the trueness of the bore. Note that if the bore droops, or bows to the side, this will impede the escape of the ball, and thus increase the pressure that the barrel must withstand (Hoskins 65).
Flaws may develop (or worsen) as a result of use (or misuse). Firing the gun too rapidly so that it overheats, overcharging the gun, and ramming the gun too hard all can create problems. Bronze has the great advantage that it tends to "crack and bulge before it bursts," unlike iron. (Id.).
Now let's discuss the Gribeauval system, which gave the French the best artillery in late-eighteenth-century Europe. Much attention was given to tightening the manufacturing tolerances for both the bore and for the cannon balls it fired. Rather than merely judge by eye whether the bore was dimensionally correct, the Gribeauvalist inspectors used a caliper gauge to measure the diameter to within 0.025 mm. (Alder 150).
In canon, Grantville's machine shops quickly demonstrated that they could do even better. Early in the new time line, Ollie Reardon manufactures new three-pounder cannon for Gustav Adolf. The metal is soft bronze, in which he drills out the bore on a lathe. He notes that ideally the finish cut would be with a reamer. (Flint, 1632, chapter 46). Whether reamed or not, the final product impresses Torstensson, Gustav's Chief of Artillery: "Those bores are perfectly identical!" In response, Rebecca shows him a micrometer, and explains that it has an accuracy of 1/1000th of an inch (one mil). (chapter 47).
Table 1-3 shows that even in Elizabethan times, there was a trend toward heavier armament:
Table 1-3: Ship Armament Distribution in Elizabethan Navy
(1) Nelson 108, (2) Nelson 110
*stone throwers (Port-pieces and fowlers were small stone throwers, virtually obsolete by 1635—Lavery 103)
I don't have a bronze vs. iron breakdown for 1585, but in 1592, naval guns were 79% bronze. (Walton 220). Thus, there was also a trend toward replacing bronze with cast iron.
This information is still relevant as of RoF; both ships and guns typically remained in service for several decades. The British warships in active service in 1631 included the British Bear (40 guns, 1580), Adventure (26 guns, 1594), Warspite (32, 1596), Nonsuch (32, 1605), and Assurance (34, 1605). As for guns, on the Portuguese Santissimo Sacramento (launched probably in 1653; sunk 1668), the bronze guns are dated, either explicitly by the caster, or implicitly by design. Nine were cast before 1600. Eleven, between 1600 and 1650. Five were just identified as mid-1600s, and one was 1653. (Guilmartin). On the Kronan (sank 1676), one gun was cast in 1514 (Hoskins 18).
It would of course be nice to have comprehensive data for a date closer to the RoF (1631). I have found the Royal Ordinance Inventory for 1637 (Collins), but that's for the army. While the Royal Ordinance also supplied the navy, the latter would have requisitioned a different assortment.
What I can provide is data for individual ships; table 1-4 attempts to correct the usual British bias by providing some French, Danish, Swedish and Dutch examples.
Table 1-4: Sample Continental Warships Built OTL 1625-1635
(1) Couronee (2) Royal (3) Gota Ark (4) Perle (5) Trois Rois (6) Maagd van Dordrecht (7) Norske (8) Mars (9) Jonge Prins (10) Eenhorn. Source: 3decks.com.
By way of comparison, the principal Napoleonic battleship, the "74", usually had 28x32pdr, 28x18pdr, 18x9pdr. (Lavery 121).
In the table, I introduce the metric "broadside weight," the total weight of shot that can be fired at one time. This is probably a better measure of the power of a warship than just the nominal number of guns.
From a ship design standpoint, another important metric is the ratio of that broadside weight (pounds) to the ship displacement (tonnes); for the Swedish navy, it was around 0.4 in the 1630s, but increased to 0.75 in 1671. (Glete 571). In that year, the Kronan carried an armament of about 180 tonnes, 8% of its 2,300 tonne displacement. (572).
Horizontal Distribution of Guns
We may recognize three basic gun arrangements: predominantly frontal; predominantly broadside; and turreted. The Mediterranean galleys are in the first category. One of the more powerful of the Venetian galleys at Lepanto (1571) might have a 52 –55 pound full cannon, flanked by an inner pair of 12-pounders and an outer pair of 6-pounders. And it could have a second deck, carrying swivel guns, as was certainly the case for the larger Spanish galleys. (Guilmartin, 322-3). In the eighteenth and nineteenth centuries one could also find heavy frontal armament in certain specialized warships, bomb ketches and rocket ships. In the twentieth century, we have a similar arrangement on torpedo boats and missile boats. And attack submarines may be said to have a spinal armament, firing torpedoes from bow or stern.
Most warships of the late-sixteenth through mid-nineteenth centuries were designed to deliver powerful broadsides, but had rather weak bow and stern armament. Once the "line ahead" formation and related tactics, which lent themselves to delivering broadsides, were developed in the mid-seventeenth century, this was particularly true of capital ships. A frigate or lesser vessel was more likely to have chase guns.
Despite the importance of the broadside, seventeenth-century French warships tended to have relatively powerful bow and stern armament, because they were used in the Mediterranean against galleys. This required some adjustment in the hull to provide a good firing arc. (Langstrom 167). In general, since the number of bow and stern guns was limited by space, those tended to be the ones with the best range and accuracy. (ChapelleHASN 12).
It's perhaps worth noting that warship designers of the second half of the nineteenth century were "ram-crazy"; this in turn led to an undue emphasis on frontal firepower for steam-powered ironclads.
For a ship with broadside armament, the length determines how many guns it can carry per deck. Length was limited by structural concerns; local inequalities of weight and buoyancy would cause it to droop in the center (hogging) or sometimes at the ends (sagging). These in turn imposed strains on the hull; they were proportional to the square of the length. Wooden-hulled warships consequently weren't much longer than 200 feet; a British first rate of the 1745 Establishment was 179 feet at the gun deck. (Ireland 41).
Of course, the number of guns carried on a deck of particular length depended on the spacing between the gunports, and how close they came to the bow or stern. On the Dauphin Royal (1735), 74 guns, there were 13 ports to a side, the foremost about 18 feet from the stem and the aftmost about 10 feet from the stern. The port width was 2'10" and the distance between ports (edge-edge) was 7'7". (du Monceau 4).
Gunport spacing was limited by the area and crew needed to work the guns; the more powerful the gun, the greater these were. Gunport breadth, for example, was 3 feet for a 48-pdr and 1.5 for at 4-pdr (Id). The spacing was also affected by the framing; you didn't want to cut through a frame and weaken the hull. A mid-seventeenth-century Dutch admiralty had these rules of thumb: gunport spacing (center-center) 20 shot diameters; height, six diameters; width, five (Hoving 104). A mid-eighteenth-century rule allows for 25 shot diameter spacing and 6.5 diameter width, with the sill 3.5 diameters above the deck (Davis1984,110).
In the British 1745 establishment, no warship had more than 28 guns on a single full deck. However, there were post-establishment British warships, such as the First Rate Victory (1765) and the "Large" class 74s, with 30 guns on the lowest gun deck (Lavery 121ff). And in 1764, du Monceau, said that a 112-gun French warship had 32 guns (24-pdr) on its second deck.
If you wanted more guns than a single full deck could accommodate, you put them on the quarterdeck or forecastle, or, if that still wasn't enough, you added a second (or if need be a third) full deck.
The mid-nineteenth-century introduction of iron and steel construction allowed warships to be lengthened, and thus history has some examples of some long "broadside ironclads." The longest of these was the HMS Minotaur (1863), 407 feet long, a sail/steam hybrid. There were also two-decker broadside ironclads, such as the French Magenta (1862), 282 feet long. (Neilson).
Broadside guns had a limited firing arc. In Napoleonic warships, the range of traversal was 40 –45 degrees before or abaft the beam; this was apparently an improvement on earlier warships (O'Neill 71). However, in steam ironclads like HMS Warrior, the gunports were narrowed, thereby reducing the arc of fire (Lambert 46). The theory was that with steam propulsion, they weren't subject to the vagaries of the wind, and therefore could maneuver as needed to bring the guns to bear. Moreover, firing at extreme angles reduced the rate of fire. I also figure that the narrower gunports meant that the guns were less vulnerable to counterfire.
I believe the first turret ship was the wooden Royal Sovereign (1857); Eriksson's ironclad USS Monitor (1862) was the first to engage in battle. The advantage of the turret was that by rotation it could bring its gun(s) to bear in any direction, save for those obstructed by the ship's superstructure (including funnels, masts, and other turrets). Because of the size and expense of the turret, the tendency was for turreted warships to be fitted with a small number of very powerful guns. For this discussion "turreted" may mean a true turret (armor rotates) or a barbette (armor stationary).
Sails, masts, spars and stays would of course restrict the firing arcs; nonetheless, many early turreted warships were hybrids (sail/steam) because of doubts as to the reliability of the engine.
This led to a variety of curious expedients. On the ill-fated HMS Captain (1869), the two turrets were on the lower (main) deck, and the masts were stayed to the upper (hurricane) deck. I would imagine that this arrangement would limit how high the guns could be elevated. The hurricane deck was dispensed with on the double-turreted HMS Wyvern and HMS Scorpion (1863), on which the turrets flanked the main mast. Captain Coles proposed use of iron shrouds and stays. (Breyer 34).
HMS Devastation (1871) was the first turreted warship without rigging (it had a central mast for signaling and observation). HMS Inflexible (1876) had two screws driven by compound steam engines, and two masts that could carry 18,500 sf sail (Wikipedia). The latter was removed in 1885. (Breyer). While I am not aware of later turreted warships with sails, the broadside-armed HMS Calypso (1883) was ship-rigged (Ireland1997, 36) and the Russian cruiser Rurik (1892), barque-rigged.
Early turreted warships included those with one (USS Monitor), two (USS Onondaga) and even three (USS Roanoke) turrets. With multiple turret designs, one has the concern of where to place the turrets. The most obvious arrangement was to place them single file on the centerline. The obvious problem was that a bow turret couldn't fire directly astern, and a central turret (as on the HMS Monarch (1868)) couldn't safely shoot fore or aft.
One alternative was to mount the extra turrets on the side (wings). This increased the frontal fire at the expense of broadside fire. In theory, wing turrets could be staggered, and fire if need be across the deck . . . but that tended not to be too good for the deck. And the centerline design was structurally sounder.
Another option was to stack the turrets, like the tiers on a wedding cake. On USS Kearsarge (1898), the double-decker turrets turned as a unit. It's reported that the vibration of the 13" guns below interfered with the firing of the 8" guns above. (cityofart.net)
The 1870s Italian navy experimented with a "diagonal reduit", in which two turrets were mounted near the center of the ship but diagonally offset from it. (Breyer 33).
A single turret could carry one, two or even three guns, but if it attempted to fire multiple guns simultaneously, "invariably, one of the guns was thrown off target by the firing of the first weapon." (Kaufmann 5).
With muzzle loaders, the turrets had to be of large diameter, but the guns short-barreled, so they could be run back and reloaded inside. (Ireland1997, 38).
The mechanisms of turret gun laying and loading are discussed in part 2, and the armoring of turrets in part 5.
Vertical Arrangement of Guns
Positioning the gun on a higher deck has the advantage that the gunports are less likely to be forced to close as a result of rough sea conditions (Laing 76). Raleigh urged that the ship be designed and laden so that the lowest tier of ordnance was four feet above the water (Creuze 17). An upper deck gun will also have increased range (as predicted by Torricelli) and can take advantage of plunging fire (shooting at the flimsy enemy deck, not the relatively stout side). However, if the enemy is close at hand, the gun might not be able to depress enough to fire upon it, and the higher the guns are, the higher the ship's center of gravity must be, reducing its initial lateral stability (but the higher freeboard does provide some compensation by increasing the angle of vanishing stability).
In the fifteenth century, ships had guns mounted high up, in the aptly named forecastles and sterncastles. The size and number of these guns was limited by their effect on stability. In the early-sixteenth century, gundecks and gunports were introduced. Since the armament was lower, it could be made heavier. (Svensson 16). As broadsides became more effective, the superstructures became less useful and were reduced in size. The early-seventeenth century was a transitional stage in which the capital ships mounted heavy broadside armaments, but still had significant superstructures.
The depth (and draft!) of the ship limits the number of gun decks. Over the course of the sixteenth century, a second and then a third gundeck (~1591) was introduced. (Creuze 15). The Dutch didn't use three-deckers, but the English and French did. (Anderson 158). British designers of the late-eighteenth century found that three-deck 80-gun ships were top heavy; two-deck 80s were too long for their height, and hogged (drooped amidships); the two-deck 74s were ideal and, even though they were considered to be of the "third rate," became the most common "battleships" in "foreign service." (Millar 9).
On a Georgian frigate, the lower deck was called the gun deck but had no guns (Millar 10). But that did help ensure that the upper deck was safely above the water.
For the British navy, there was no systematic distribution of the different gun sizes among ships of different classes, and among the different decks of a given ship, until 1677, when it adopted a "solemn, universal, and unalterable adjustment of the gunning and manning of the whole fleet." (Tanner 233ff). This was altered (snicker) by the "establishments" of 1691, 1706, 1719, and 1745. After that warship design became somewhat more diverse again.
After armor was introduced in the nineteenth century, warship design became "weight critical"—the hull displacement provided a particular amount of buoyancy, and the ship couldn't be heavier, so designers had to make compromises vis-a-vis weight of guns, engines, armor, and even fuel and ammunition carried.
As a loose rule of thumb, gun weight is proportional to the cube of the caliber (Meigs 204) and thus, for roundshot, proportional to the shot weight. For early-nineteenth-century British iron guns, gun weight was 170 –411 times the latter. (Beauchant 102). Big guns have greater range, but small guns have a higher rate of fire.
We have already alluded to the fact that bronze guns could be made lighter than cast iron ones of the same caliber; steel guns had a similar advantage over their predecessors, because of steel's greater tensile strength per unit weight.
Guns designed to only fire shells (hollow projectiles) could be lighter than those firing solid shot; shells were lighter than solid shot of the same caliber; hence less powder was needed to project them; hence the gun barrels could be thinner. Or, keeping gun weight the same, you could increase caliber. The Paixhans 80-pounder shell gun (1837) weighed the same as the traditional 36-pounder. (Tucker 1320).
There's some data on crew size in Table 2A. In early nineteenth century French naval service, 14 men attended a 36-pounder; 12, a 24-pounder, 10, an 18- or 12- pounder, 8, an 8-pounder; and 6, a 6- or 4-pounder. (Douglas 149). A carronade only needed 4 men. (163).
Miller (57) provides the rule of thumb that one man was required for every 5 cwt. (112 pounds) of gun weight, although I think that's on the low side. However, he makes the point that gun crews changed constantly; if only one side were engaged, the free crews would come over to help; but crewmen would also be pulled off to handle the ship or to form a boarding party.
Gun Loading; Rate of Fire
It's dangerous to assume that the rate of fire was as good in the 1630s as in the more familiar Napoleonic period (Hornblower Syndrome!).
A modern crew of four handling a replica sixteenth-century wrought iron breechloader required 5 –10 minutes per shot (Konstam 40). An experienced crew might well do better, but on the other hand, handling a large muzzleloader would be more time-consuming. Elizabethan sea dogs probably just fired one broadside at point-blank range and then fought a boarding action. (Konstam 40).
"In 1646 Master gunner William Eldred stated, in The Gunner's Glasse that a maximum of ten rounds an hour could be fired from a gun, and that after forty shots had been fired an interval of an hour must be allowed to cool the piece." (Hughes 35).
The fastest fixed guns on a seventeenth- (or eighteenth-)century warship were the swivel guns. There were breechloaders with removable chambers, and by having several prepped chambers handy, one could get off several shots quickly—perhaps one a minute, at least until the preps were used up. (Konstam 40). They were short range weapons, intended for anti-personnel use, and I imagine that sustained rapid fire wasn't necessary; either the enemy boarding action was fended off, or it wasn't.
Shells cannot be fired as fast as shot because the fuses have to be prepared and adjusted; percussion fuses are less trouble than time fuses. (Owen 338).
For eighteenth-century field artillery (3 –12 pounders), a good rate of fire for an eight-man crew was considered to be two aimed shots per minute (Peterson 119), and this could be doubled by eliminating steps (such as sponging the bore) . . . dangerous, but not as much getting overrun by the enemy. Speed was affected by the weight of the piece; a 12-pounder might only get off one round a minute. (Wise 31).
The rate of fire at sea was lower. (Smaller gun crews? Ship movement?) In 1738, the 70-gun Hampton Court "fire 400 rounds in twenty-five minutes which suggests that each gun fired about one round every two minutes." (Rodger 540). The USS Constitution could fire its 24-pounders, which had a twelve-man crew, one round every three minutes. (Mehl 33).
Other published estimates include one round every 3 –5 minutes for the early modern era (Volo 256); three broadsides in five minutes (Hill 55); at best one round a minute for the Napoleonic British navy (Miller 58); for best crews under perfect conditions, one round every four or five minutes in 1660 and one a minute in 1756 (Ireland 48).
Gunlocks improved rate of fire; Collingwood's flagship Dreadnought "could fire her first three broadsides in three and a half minutes." (Rodger 540). Such a firing rate could not be sustained; the gunners would tire; there would be casualties; smoke would slow down the aiming process.
Note that the British and American crews of the Napoleonic period typically got off 1.5 –3 times as many shots as a French or Spanish opponent. (Toll 7). The 74-gun Guerriere at Minorca (1756) fired 659 rounds in 3.5 hours (5.5 rounds/hour), and another French ship averaged 6 rounds/hour at the Saintes; either the crews were less handy or the French were deliberately taking their time. (Rodger 540).
The heavy rifled breechloaders of HMS Warrior (1861) were a bit faster than the old smoothbore carriage guns, firing perhaps once a minute. On the other hand, the rifled muzzle loaders were very slow. To reload, the barrels had to be fully depressed and sometimes they had to be traversed to the fore or aft position, too. That gave them a rate of fire of just one shot every three minutes. When breechloaders were reintroduced, those with the full screw closure only improved the situation a little, to once every two minutes. (Hill 55).
The elevating screw increases accuracy but not necessarily speed. In tests at Shoeburyness, a 40-pdr rifled breechloader fired 10 rounds in 7.5 minutes using the screw, and in just 6 minutes with the wedge. (Owen 337).
In the ACW, the big guns were slow. With the 15-inch Dahlgren, the average time between shots was 6 minutes; depending on conditions, it might take 3 –10 minutes to fire again. On the other hand, a long 32-pdr or 9-inch shell gun might be fired once every forty seconds. (Canfield).
Late-nineteenth-century breechloading deck guns, with pivot mounts, appeared to have firing rates of 10 rounds/minute. (Mehl 81, 85).
Even with the same model of gun, rates of fire will differ from ship to ship. In 1902, with the Mark VII 6-inch quick-fire, nine British warships exhibited prize firing rates that ranged from 4.17-7.38 rounds/minute. With heavier guns the range was 0.62 –1.25. (Brassey 38).
Rate of fire can be limited by barrel overheating. If the barrel becomes too hot, there are variety of potential problems, including increased erosion (thus loss of accuracy over the long term) and self-ignition of propellant. Barrel liquid-cooling systems have been used with some rapid-fire twentieth-century naval guns. (Wu).
In 1820s and 1830s the French experimented with canon foudre (drum cannon), "equipped with a carousel of multiple powder chambers that could be pre-loaded." It was not a success; the seal between the chamber and the barrel was inadequate. (Mehl 36).
The logical solution was to use multiple barrels (i.e., a volley gun), rather than multiple chambers, as on the Swedish Nordenfelt 25 mm machine cannon (1877). It had a rate of fire of 120 rounds/minute, and an effective range of 1500 meters. This was a semi-automatic, gravity-fed weapon. (62).
On the Nordenfelt, the four barrels were fixed, horizontally parallel. Another approach was the Hotchkiss system revolving cannon; an 1896 Russian model fired 80 rounds/minute to 2700 meters. (63). Another source claimed that 12 aimed shots/minute at 4000 yards was possible. (Ireland1997, 42).
In the canonical Baltic War, the USE army had Requa-style volley guns. The USE navy wanted them for its timberclads, for suppressing cavalry raids on river shipping, but the army was given priority. (And fortunately, the air force conceded that it was "at least two generation of aircraft away from mounting machine guns.) (1634: TBW, Chap. 5). Ultimately, the USE navy went with a pivot-mounted Reffye-style mitrailleuse, having twenty.50 caliber barrels. Unlike the volley guns, these were fired in succession; maximum rate of fire was 60 aimed or 100 unaimed shots per minute. It had removable breechblocks and was loaded twenty rounds at a time. (1634: TBW, Chap. 41).
Grantville Firearms Roundtable, "How to build a Machine gun in 1634 with available technology: Two alternate views" (Grantville Gazette 4) may be of interest.
Whether at the breech or the muzzle, manual loading was the norm for big guns until the nineteenth century. When turrets were equipped with steam power for traversing the gun, thought was given to whether this same power could expedite the loading process. On Eads' USS Winnebago, steam power was used to lower the gun platform to a (safe) loading position (cityofart.net), but it didn't actually load the projectiles.
On the USS Indiana (BB1, 1895), the 13-inch gun turrets were semi-automatically loaded. They were equipped with hydraulically-powered ammunition hoists, the hoisted car having separate compartments for the powder and the projectile. However, in the magazine, these compartments were loaded by hand. A hydraulic rammer pushed the projectile into the gun breech. It's not clear to me how the projectile got from the hoist car to the rammer. (Fullam 187). A somewhat similar hatch loading system was used on the 16-inch rifled muzzle loaders of the HMS Inflexible (1895), but of course it communicated with the muzzle. (Ellacott 58).
In canon, Simpson's ironclads use salvaged mine hydraulics to open and close the gunports and perhaps operate the blowers that suck out the smoke, but it appears that the shell and powder hoists are operated manually. (1634: TBW Chap. 38).
This article continues in Part 2, "Ready, Aim, Fire!"