3-inch gun M1918

The 3-inch M1917 was the US's first dedicated anti-aircraft gun, entering service during World War I. Only a few were built, as the similar 3-inch M1918 on a mobile mount was considerable more useful, only being replaced by the 90 mm M3 gun just prior to the opening of World War II. The M1918 was later adapated for the anti-tank role, serving as the main armament of the M10 Wolverine.

Development of the M1917 started in 1915, and as the name implies, took two years to enter service. The gun was essentially an unmodified 3-inch M1903 (76.2mm L/55) coastal-defense gun on a new mount allowing it to be aimed to high elevations. A number were used during the war. In the immediate post-war era it was developed as the 76.2mm M2, using a removable barrel liner. In 1928 it was further improved in the 76.2mm M4 by using a thicker removable liner that eased manufacturing.

For mobile use the original coastal gun was too heavy, so a smaller version was developed as the 3-inch M1918. For this role the barrel was cut down in length, to 50 calibers from 55, and a new breach was introduced to fire smaller rounds of 212 cubic inches from 293. Like the adaptation that created the M2, the M1918 was also fitted with a removable liner in 1928, becoming the 3-inch M3. Another upgrade was started in 1931 as the T8, and then T9, but these projects were cancelled in 1938 when the 90 mm gun was selected in their place.

In September 1940 a project started to adapt the M3's to the anti-tank role, starting with the T9 experimental model but equipping it with the breech from the 105mm M2 howitzer allowing it to fire larger rounds. The gun was originally intended to be mounted on the M5 self-propelled gun, which they eventually gave up on, and it was too large as-is to mount on the M4 Sherman. As a result, although the gun was accepted for service as early as December 1941 as the 3-inch M5, production was curtailed and it was finally introduced only in small numbers mounted on a towed carriage and featuring a large protective shield for the gunners. Unfortunately it suffered in combat due to faulty rounds, and was practically useless against tanks until 1944 when improved ammunition was introduced.

A final adaptation was the 3-inch M7, which included minor modifications for mounting on the M10 Wolverine. The M7

Original fixed-place anti-aircraft gun introduced in 1917.

Mobile anti-aicraft gun using a cut-down version of the original M1917 gun and a new mount.

Variant of the M1917 with a removable barrel liner.

Variant of the M1918 with a removable barrel liner.

Version of the M2 with a thicker liner for easier manufacturing.

Version of the M3 adapted for anti-tank use. Available in limited numbers.

Version of the M5 for use on the Wolverine.

• LemaireSoft encyclopedia (somewhat confusing, information is spread over several pages)
• M5 & M7 armor penetration table