10-inch/31-caliber gun

10"/31 caliber Mark 1 Mod 1/ 10"/35 caliber Mark 1 Mod 2/ 10"/30 caliber Mark 2 Naval Gun
10"/31 caliber Mark 1 Mod 1/ 10"/35 caliber Mark 1 Mod 2/ 10"/30 caliber Mark 2 Naval Gun
	Fitting one of the 10-inch main guns to the front turret of USS Miantonomoh (BM-5) at the New York Navy Yard, circa 1890.
Type	Naval gun
Place of origin	United States
Service history
In service	1890
Used by	United States Navy
Wars	Spanish–American War; World War I;
Production history
Designer	Bureau of Ordnance
Designed	1885
Manufacturer	U.S. Naval Gun Factory
Unit cost	$38,566.58
Variants	Mark 1 Mod 1, Mark 1 Mod 2 and Mark 2
Specifications
Mass	Mark 1 Mod 1: 57,500 lb (26,100 kg) (without breech); Mark 1 Mod 2: 61,000 lb (28,000 kg) (without breech); Mark 2: 50,200 lb (22,800 kg) (without breech);
Length	Mark 1 Mod 1: 329.1 in (8,360 mm); Mark 1 Mod 2: 365.5 in (9,280 mm); Mark 2: 329.1 in (8,360 mm);
Barrel length	Mark 1 Mod 1: 312.8 in (7,950 mm) bore (31 calibers); Mark 1 Mod 2: 349.54 in (8,878 mm) bore (35 calibers); Mark 2: 300 in (7,600 mm) bore (30 calibers);
Shell	510 lb (230 kg) armor-piercing
Caliber	10 in (254 mm)
Elevation	Marks 1 and 2:-3° to +13.5°; Marks 3 and 4:−3° to +15°;
Traverse	−150° to +150°
Rate of fire	1890s: 0.66 rounds per minute; 1900s: 2 – 3 rounds per minute;
Muzzle velocity	2,000 ft/s (610 m/s)
Effective firing range	20,000 yd (18,000 m) at 15° elevation

The 10"/31 caliber gun Mark 1 Mod 1 (spoken "ten-inch-thirty-one--caliber") and the 10"/35 caliber gun Mark 1 Mod 2 were both used for the primary batteries of the United States Navy's Amphitrite-class monitor Miantonomoh. The 10"/30 caliber gun Mark 2 was used as main armament on the remaining Amphitrite-class monitors, the monitor Monterey, and the armored cruiser Maine.

The Navy's Policy Board called for a variety of large caliber weapons in 1890, with ranges all the way up to 16-inch (406 mm). This 10-inch (254 mm) gun had been in development since 1885. The Navy desired a light weight heavy weapon with a 10-inch bore to arm their coastal monitors and the armored cruiser Maine, which would later be classified a "Second Class Battleship." The 10-inch/31 caliber gun would be the first heavy breech loader (BL) gun in the "New Navy" and be the ancestor to all large caliber BL guns built in the United States.