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. ( 1633Chap. 4; 1634: TBWChap. 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.

Gunmetal

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.

Bronzefirst 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 ironis 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.