Each of the Iowa-class battleships (such as the USS Iowa or USS New Jersey) was equipped with nine 16-inch (406mm) guns, each capable of firing shells weighing over 2,000 pounds (about 900 kg) at a range of up to 20+ miles (32+ kilometers). Firing all three turrets (a full broadside) results in a tremendous recoil force. This force pushes the ship slightly in the opposite direction of the gunfire.
How Far Does the Ship Move?
While the exact amount of movement can vary depending on a number of factors (such as the exact weight of the shells, the ship's current speed, and sea conditions), the general movement can be estimated as follows:
Recoil-induced movement: The ship typically moves by a few inches to a foot (roughly 5-12 inches, or about 15-30 cm) laterally to one side after firing a full broadside. This movement is generally very small but noticeable in terms of the ship’s stability.
Why Does This Happen?
The force produced by the recoil of the 16-inch guns is so immense that it has a physical effect on the entire ship. When the guns fire, they push backward with great force, causing the ship to react by shifting in the opposite direction, just like a gun recoiling when fired.
However, battleships like the Iowa-class were designed with stabilizing systems, including the positioning of the turrets and the ship's hull shape, to counteract this effect. Additionally, the sheer size and mass of the ship make the movement relatively small compared to the forces involved.
Effect on Firing
The recoil of the guns is so substantial that the Iowa-class battleships had to account for it when firing to maintain their stability and to ensure accuracy. The ship would often "settle" after firing, and a well-trained crew could ensure that the ship remained on target despite the recoil effects.
After a full broadside, the ship might need to adjust its aim for the next salvo due to slight shifts in orientation.