12in Howitzer on Railway Mount

The 12in Howitzer on Railway Mount was one of the more advanced designs of railway artillery produced for the US Army, but like most American designs didn’t arrive in time to see service in the First World War.

The weapon was designed in response to a request from the American Expeditionary Force in France, where there was a demand for a 12in mortar with a range of 20,000 yards, with a range of traverse of at least 20-30 degrees to either side of the centre line (40-60 degrees at each end, for a total of 80-120 degrees), using a similar emplacement system to the 8in gun and 12in mortar, both of which could be emplaced and firing within an hour.

In order to satisfy this request a new gun was designed. The resulting gun was a 12in 20 calibre howitzer, model 1919 (sometimes called a ‘long mortar’), with a built-up barrel. It had an interrupted thread breech block with a mechanical firing mechanism.

The gun was carried in a tubular grid cradle, which surrounded the breech end of the barrel. Smaller tubes were built into the cradle to take the recoil system, which consisted of two hydraulic recoil cylinders on either side of the base and one pneumatic recuperator above the cradle.

The gun cradle was carried on a top carriage with cast steel sides and a working platform that carried the crew and ammo table. This was all mounted onto a rack carried on a base plate, and could be rotated using a rack and pinion system connected to a hand gear. One complete turn of the wheel turned the gun by 1.028 degrees.

The elevation mechanism used a circular rack bolted to the right of the cradle, connected to a pinion that was connected to a hand wheel by spur gears. It was similar to the system used on the 16in howitzer Model 1918.

A new type of railway car was developed for the 12in howitzer. The old type, used on the 8in gun and 12in mortar, had been made up of steel side girders with cross beams and a working platform to provide some stability, but they tended to buckle. The 12in howitzer car was made up of three parts - two ends made of structural steel and the centre section, carrying the gun, made as a single cast. This gave it a very rigid base. The central section was open in the middle, allowing the gun to recoil much further.

The new carriage was emplaced in a similar way to the older guns. The gun carriage was raised up on jacks. Steel firing beams were placed across the ties outside the rails. Sleepers were placed across these beams and the carriage lowered onto the sleepers and beams. The main central section sat directly on the steel firing beams. Outriggers were attached to increase the stability of the gun.

The 12in howitzer railway mount wasn’t produced in time for service in France in 1918, but some were used by the US coastal artillery in the inter-war years, where their 360 degrees of traverse was considered to be useful.





Barrel Length


Gun length

6.69m (263.6in)

Weight in action

88,620kg (195,243lb)


20 to 60 degrees


360 degrees

Shell Weight

317.73kg (700lb) HE, 42.66kg explosives

Muzzle Velocity

594m/ s (1,950 ft/sec)

Maximum Range

19.74km (21,600 yards)

Rate of Fire

25 rounds/ hour


Books on the First World War | Subject Index: First World War

How to cite this article: Rickard, J (11 March 2019), 12in Howitzer on Railway Mount , http://www.historyofwar.org/articles/weapons_12in_howitzer_railway_mount.html

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