Naval Gazing Main/Main Guns Part 1
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April 22, 2018
Main Guns Part 1
The ultimate purpose of a battleship is to carry guns. Everything else - armor, engines, living quarters - ultimately exists to support the delivery of high-velocity steel to the enemy. As such, it's a topic which deserves a close look.
The gun deck of HMS Warrior
As you probably expect by now, we'll start with HMS Warrior. She carried a total of 40 guns: 26 68-pounder smoothbore muzzle-loaders, 10 110-pounder rifled breech-loaders,1 and 4 40-pounder rifled breech-loaders.
68-pounder replica aboard Warrior
Odd though it may seem, the best of these guns were the 68-pounders, firing 8" iron shot. The last and largest of a long line of British cast-iron smoothbores, these guns had developed a formidable reputation, most famously in battering the walls of Sevastopol. They were the only weapons capable of penetrating the 4.5" armor of Glorie, and the original plan had been to arm Warrior with 42 of them. However, the development of the Armstrong breechloaders caused these plans to be revised, with some of the 68-pounders replaced.
Diagram of 110-pounder breech mechanism
Unfortunately, while the Armstrong guns were a definite step forward technologically, they were a step backwards from an operational standpoint. Even on a good day, the 110-pounder was not as effective as the 68-pounder at piercing armor,2 and there were many bad days. To load the gun, the large, hollow screw at the breech was loosened, and the block it secured lifted out. The gun was loaded through the center of the screw, and the block replaced. The problem was that the crew simply tightened the screw as much as they could, and there was no positive closed position. It's usually claimed that 21 Armstrong Guns suffered 28 accidents in the course of firing only 365 rounds during the bombardment of Kagoshima, but this doesn't look to be true.3 In any case, the gun was not a success, and was swiftly relegated to coastal defense duties.
110-pounder on a pivoting slide mount on Warrior's deck.
Most of Warrior's guns were mounted much like guns had been for centuries, on wheeled carriages secured with rope to absorb the recoil.4 They were run in and out by their crews, much as had been done in Nelson's day. The gunports were narrower than normal, and the guns pivoted around a bolt in the sill instead of further back. However, the ports were taller than was normal on a battleship, to allow Warrior to fight at long range. The gun was supported in the carriage by a pair of cylinders on either side called trunions, and wedges were used to raise and lower the muzzle.
12" RML on HMS Hotspur
The failure of the Armstrongs soured the RN on breech-loaders, but the drive for improvement over the smoothbores was still there, and the Rifled Muzzle-Loader (RML) was the result. This gun was built around a steel tube, with wrought iron tubes wrapped around it for greater strength. The shell had studs on the side, which engaged the grooves in the barrel. The resulting gun was cheap and safe, but not particularly effective. It was introduced starting in the mid-1860s, and was made in sizes ranging from 6" up to the massive 16" guns used on HMS Inflexible.
Construction diagram of RML 12" 25-ton gun
The gun's shape, much thicker on the breech end, was a result of the powder at the time. Black powder burns quickly, which means that for a given muzzle velocity, the pressure at the breech must be high, tapering off quickly as the projectile moves down the barrel. Projectiles improved in parallel with guns, as the balls of previous guns were replaced by elongated shot and shells. The first major innovation was Palliser shot, made of cast iron and chilled to give it reasonable armor-piercing capability.5
Ericsson turret of Monitor
There was also significant innovation in the field of mountings. Even while Warrior was under construction, inventors on both sides of the Atlantic had decided that it would be better to mount guns in a rotating structure on top of a ship. This became known as a turret, by analogy to the turrets of castles. John Ericsson's turret, used on the famous Monitor, rested on a central spindle, which had to be lifted when the turret turned. The turret developed by Cowper Coles in the UK used a roller path below deck instead. In the end, the Coles turret won out, as it scaled better to heavier turrets and was always ready to fire.6
Coles turret of HMS Inflexible, showing external loading mechanism7
While it might seem intuitively obvious that the turret would kill off the muzzle-loader, this was not in the case. In fact, external loading mechanisms meant that muzzle-loaders actually required a smaller, simpler turret than breech-loaders. The rammer was mounted under the deck, and the turret was trained and depressed to bring it into line with the rammer. This meant that ammunition didn't have to be passed into the turret, either. Initially,...