10-inch/31-caliber gun

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.

Mark 1

The 10-inch Mark 1 was a built-up gun constructed in a length of 31 caliber, Mod 0 and Mod 1, and also 35 caliber, Mod 2. These were both mounted in pairs on Mianonomoh and numbered 1–4 by the Navy. Both of the Mod 0 and Mod 1 guns had a tube, jacket, with the Mod 1 having a thicker jacket, and 15 hoops with a locking ring. The hoops started 5.91 in (150 mm) from the breech and extended to the muzzle. The Mod 2, was a 35 caliber gun of similar constructions but had only 14 hoops with a locking ring. These were all constructed of gun steel.