The 3-inch mine defense guns were part of a comprehensive plan of new fortifications specified by the
Board of Fortifications of 1885. The new forts initially included guns up to 12-inch (305 mm) on
disappearing carriages, to conceal the fort from observation from the sea. The 3-inch guns were the smallest of these guns, intended to protect
remotely controlled minefields against
minesweepers. For most of their service they were operated by the
United States Army Coast Artillery Corps. They were based on an 1897 Board of Ordnance and Fortification requirement for a weapon intermediate between
6-pounder (57 mm) guns and 5-inch (127 mm) guns.
M1898 The M1898 was the first of the new 3-inch guns developed. It was manufactured by
Driggs-Seabury and was on an M1898 "
masking parapet" retractable carriage. This was a proprietary term Driggs-Seabury coined to distinguish their carriage from the similar "
balanced pillar" carriage of the
5-inch gun M1897, built by other manufacturers. Unlike the disappearing carriages of most larger weapons, the carriage could only be retracted when the gun was at a particular traverse angle (in most installations 90° off the emplacement axis), thus it provided no concealment when in action. Approximately 120 of these were built between 1899 and 1903, and at least 111 of these weapons were emplaced between 1899 and 1905. Official correspondence between Major Louis R. Burgess, commander of the
Artillery District of Mobile (Alabama), and senior
Ordnance Corps officers began in December 1912. This brought up several deficiencies in the M1898 weapon, including the necessity of clamping the elevation and traverse changing the gun's elevation and interfering with tracking a moving target. The rubber eyepiece on the telescopic sight did not fully protect against injury when the weapon was fired; an injury to Sgt. Payne of the 164th Company was noted, with the remark "the lateral kick and vibration of the carriage upon recoil is destructive to the morale of the gun pointer". The lights provided for night firing also tended to become unscrewed, and the lamps for the sight's deflection scale were overly bright, apparently interfering with observation of the target. Major Burgess recommended switching to the barbette carriage M1903 and its firing lever system (as used on the 3-inch gun M1903), or modifying the masking parapet carriage with traverse and elevation gearing. In March 1913 the ordnance officers considered disabling the carriage in the up position by partially filling it with concrete. This had already been tested at
Sandy Hook Proving Ground, and was gradually implemented for most M1898 carriages as the M1898MI carriage through mid-1917, though some were still unmodified in March 1919. The disabling of carriages had little negative impact; the weapon was small enough that the risk of observation from the sea was minimal. Also in 1917, another serious deficiency appeared in the M1898: the piston rod (unclear if this was the recoil piston rod or the carriage raising piston) sometimes broke when fired, presenting a hazard to the gun crew and taking the gun out of service until repaired. The
secretary of war recommended the use of a longer lanyard to fire the gun. Also, a new
dual-purpose mount to allow antiaircraft fire was considered but never developed. In March 1920 the ordnance and coast artillery leadership determined that the M1898 should be declared obsolete and removed from service. All of the M1898 guns and carriages were removed from service in 1920, with the carriages being scrapped. Except in a few cases, they were not directly replaced at the forts. In November 1931 the guns were declared obsolete, with many being donated to communities as war memorials and the rest scrapped. An unusual emplacement for the M1898 guns was at
Fort Mott, New Jersey, near
Fort Delaware. Two guns were in a massive
casemated emplacement named Battery Edwards, converted from an 1870s
magazine. At this location it was determined that the minefields needed maximum protection.
M1902 The M1902 was functionally similar to the M1898, but was manufactured by
Bethlehem Steel and was on a non-retractable pedestal carriage. 60 of these weapons were built and emplaced 1903–1910. It was not the same weapon as the
3-inch M1902 field gun.
M1903 The M1903 was a slight improvement on the M1902 with the bore lengthened from 50
calibers to 55 calibers for increased range. References vary as to whether the bore was lengthened or not, but the increase in overall length supports that it was. The weapon was manufactured by
Watervliet Arsenal and was on a non-retractable pedestal carriage. 101 of these weapons were emplaced 1904–1917.
Basis for anti-aircraft guns The
3-inch gun M1917 was a
World War I-era US-made
anti-aircraft gun based on the 3-inch gun M1903. It was designed for a fixed mounting and remained in service, primarily at Coast Artillery installations, through
World War II. It was determined that the weapon was too heavy and had too much recoil for mobile mountings, so a new weapon based on the barrel of the lighter and less powerful 3-inch gun M1898 was developed, designated the
3-inch gun M1918. This was the standard US anti-aircraft gun until partially replaced by the 3-inch gun M3 in 1930; some M1918 guns saw action in early World War II. There is some controversy as to whether any seacoast guns were actually converted into anti-aircraft guns in the development of these weapons.
Replacement As part of an across-the-board modernization, all types of 3-inch seacoast guns (with some exceptions, usually as
examination batteries) were replaced by the
90 mm gun M1 in 1940–44 during World War II, usually in new locations. The new weapons were called Anti Motor Torpedo Boat (AMTB) guns. As they were replaced, most of the 3-inch guns were scrapped, along with almost all older Coast Artillery weapons. Almost all remaining weapons, including the new 90 mm guns, were scrapped shortly after the war ended in 1945–48. ==Where used==