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US Navy Training Film MN-9321c

Public domain film from the US Navy, slightly cropped to remove uneven edges, with the aspect ratio corrected, and mild video noise reduction applied.
The soundtrack was also processed with volume normalization, noise reduction, clipping reduction, and/or equalization (the resulting sound, though not perfect, is far less noisy than the original).

The 16″/50 caliber Mark 7 — United States Naval Gun is the main armament of the Iowa-class battleships.

These guns were 66 feet (20 m) long—50 times their 16-inch (406 mm) bore, or 50 calibers, from breechface to muzzle. Each gun weighed about 239,000 pounds (108,000 kg) without the breech, or 267,900 pounds (121,517 kg) with the breech.[1] They fired projectiles weighing from 1,900 to 2,700 pounds (850 to 1,200 kg) at a maximum speed of 2,690 feet per second (820 m/s) with a range of up to 24 miles (39 km). At maximum range the projectile spent almost 1½ minutes in flight. Each turret required a crew of 94 men to operate. The turrets themselves cost US$1.4 million each, to which the cost of the guns had to be added.

The turrets were «three-gun», not «triple», because each barrel could be elevated and fired independently. The ships could fire any combination of their guns, including a broadside of all nine. Considering the large mass of the ship, compared to the mass of the projectiles, the ships barely moved sideways at all, even when a full broadside was fired. With the damping effect of the water around the hull it seems that the pressure wave generated by the gunfire was felt much more than the very slight change in lateral velocity.

The guns could be elevated from −5 degrees to +45 degrees, moving at up to 12 degrees per second. The turrets could rotate about 300 degrees at about 4 degrees per second and could even be fired back beyond the beam, which is sometimes called «over the shoulder». Within each turret, a red stripe on the wall of the turret, just inches from the railing, marked the boundary of the gun’s recoil, providing the crew of each gun turret with a visual reference for the minimum safe distance range.

Complementing the 16″/50 caliber Mark 7 gun was a fire control computer, in this case the Ford Instrument Company Mark 8 Range Keeper. This analog computer was used to direct the fire from the battleship’s big guns, taking into account several factors such as the speed of the targeted ship, the time it takes for a projectile to travel, and air resistance to the shells fired at a target. At the time the Montana class was set to begin construction, the rangekeepers had gained the ability to use radar data to help target enemy ships and land-based targets. The results of this advance were telling: the rangekeeper was able to track and fire at targets at a greater range and with increased accuracy. This gave the US Navy a major advantage in World War II, as the Japanese did not develop radar or automated fire control to the level of the US Navy.

The Mark 7 gun was originally intended to fire the relatively light 2,240-pound (1,020 kg) Mark 5 armor-piercing shell. However, the shell-handling system for these guns was redesigned to use the «super-heavy» 2,700-pound (1,200 kg) APC (Armor Piercing, Capped) Mark 8 shell before any of the Iowa-class battleships were laid down. The large caliber guns were designed to fire two different 16 in (406 mm) shells: an armor piercing round for anti-ship and anti-structure work, and a high explosive round designed for use against unarmored targets and shore bombardment…

The propellant consists of small cylindrical grains of smokeless powder with an extremely high burning rate. A maximum charge consists of six silk bags, each filled with 110 pounds of propellant…