by Werner » Wed May 07, 2008 10:46 pm
Generally speaking, that would be correct. It's also important to remember that dispersion also changes over the lifespan of the barrel liner, and over the course of a battle, as the gun tube changes temperature.
Most dispersion is caused by interference of the shock waves of adjacent guns when they are fired at about the same time. In the 1920s and 1930s, naval scientists added long spools of wire to "slow" the ignition of the middle tube, so it fired well after the others. These delay coils could also be found in other navies. Nowadays, you could order computers to fire with several millisecond delays, but in the early 20th Century, they had to rely on the physics of wire to cause such events. Other navies, like the RN, used alternate gun firing to halve the rate of fire, but greatly increase the accuracy. In the USN this was not possible, because in several classes of ships the guns were all on one slide and had to be loaded and fired as a single unit.
The Japanese Navy was probably unique in having a manned instrument which could order a slight change in dispersion aboard the Yamato, Mogami, and Tone classes.
As you can see in the illustration below, it is possible to target the "E" ring within the Pentagon with two salvos at 12 1/2 and 25 miles from the target. Of course, when the battleships were retired, there were active programs for guided projectiles, sabot and "Arrowhead" projectiles with extended range (250+ miles) and GPS accuracy. You can see the benefit when you compare a $1,000 16-inch shell to a $1 million "reduced price" Tactical Tomahawk.
In November 1987, with the doppler Radar and rebagged propellant, USS Iowa demonstrated a pattern size of 219 yards at 34,000 yards (0.64% of range), with a standard deviation of +- 123 yards (0.36% of range), probably the best performance ever demonstrated with a large gun at long range.
Generally speaking, that would be correct. It's also important to remember that dispersion also changes over the lifespan of the barrel liner, and over the course of a battle, as the gun tube changes temperature.
Most dispersion is caused by interference of the shock waves of adjacent guns when they are fired at about the same time. In the 1920s and 1930s, naval scientists added long spools of wire to "slow" the ignition of the middle tube, so it fired well after the others. These delay coils could also be found in other navies. Nowadays, you could order computers to fire with several millisecond delays, but in the early 20th Century, they had to rely on the physics of wire to cause such events. Other navies, like the RN, used alternate gun firing to halve the rate of fire, but greatly increase the accuracy. In the USN this was not possible, because in several classes of ships the guns were all on one slide and had to be loaded and fired as a single unit.
The Japanese Navy was probably unique in having a manned instrument which could order a slight change in dispersion aboard the [i]Yamato, Mogami,[/i] and [i]Tone[/i] classes.
As you can see in the illustration below, it is possible to target the "E" ring within the Pentagon with two salvos at 12 1/2 and 25 miles from the target. Of course, when the battleships were retired, there were active programs for guided projectiles, sabot and "Arrowhead" projectiles with extended range (250+ miles) and GPS accuracy. You can see the benefit when you compare a $1,000 16-inch shell to a $1 million "reduced price" Tactical Tomahawk.
In November 1987, with the doppler Radar and rebagged propellant, USS [i]Iowa[/i] demonstrated a pattern size of 219 yards at 34,000 yards (0.64% of range), with a standard deviation of +- 123 yards (0.36% of range), probably the best performance ever demonstrated with a large gun at long range.