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How To Identify U.S. 12-Inch Railway Guns

The Visually Distinct Differences Between U.S.12-inch Railway Guns and Carriage Types (Army & Navy)

The United States developed several 12-inch railway artillery systems during and after World War I for heavy fire support and coastal defense. These included Army-built mounts using surplus 12-inch coastal guns (M1895 series) and a limited number of mounts with longer 12-inch naval-type guns. Below is a comparison chart of the major 12-inch railway gun configurations, followed by detailed descriptions of each. For context, key 14-inch railway gun mounts (Army Mk I, Navy Mk II, and Army M1920) are included to highlight design differences and identification in photographs.

1. 12-inch M1918 Railway Gun (Army Mk I Batignolles Mount)

Key ID Features:

• Gun: 14"/50 caliber Navy Mk IV
• Carriage: Massive steel gunhouse with armor plating (looks like a naval turret on rails)
• Length: ~90 feet
• Recoil System: Recoil pit required under the tracks for high elevation shots (deep excavation)
• Traverse: Minimal — only via curved track segments (the mount itself doesn’t pivot)
• Axles: Usually 12 axles total (2 trucks with 6 axles each)

How to spot in photos:

• Look for a boxy, armored gunhouse that resembles a ship turret.
• No visible jacks or pivot system underneath.
• Often sitting on straight track with a deep pit dug beneath (or seen in firing pit positions).
• Gun barrel is relatively long, often pointed upward for high-elevation shelling.

1. 12-inch “Chilean” Sliding Mount (Army, 50-Caliber Gun)

Key ID Features:

• Very similar to the Navy Mk I mount, but built for Army use
• Also uses 14"/50 caliber Mk IV gun
• No gunhouse armor — mount appears more “open” or skeletal in photos
• Same recoil pit system
• Curved track used for traverse
• Fewer photos exist, as these were not deployed in Europe

How to spot:

• Looks like a Navy Mk I without the armored turret
• Long gun barrel exposed
• 12 axle trucks common
• Seen on curved track or over prepared firing pits

1. 12-inch M1918 Railway Mortar Carriage (All-Around Fire Mount)

Key ID Features:

• Gun: Same 14"/50 Mk IV naval gun
• Carriage: Longer, taller, open-sided mount, no gunhouse
• Weight distributed over 20 axles
• Recoil: Rolling recoil — the entire mount rolls backward on firing, no pit needed
• Traverse: Still needs curved track
• Higher ride height to allow clearance of gun recoil

How to spot:

•  Much longer base with 20 axles (usually 10 axles per truck)
•  Open deck mount – you’ll see lots of mechanical linkage, breech exposed
• Looks taller and bulkier, due to gun height above carriage
• May appear to be chained or braked down, indicating rolling recoil operation

Side-by-Side Visual Cues Summary:

Identifying 12-inch vs 14-inch Railway Guns in Photographs:

1. If it looks like a turret on rails: Navy Mk I.

1. If it's open and skeletal, and short: Army Mk I.

1. If it's tall, massive, long with 20 axles: Navy Mk II.

1. If it’s squarish with jacking systems and no deep pit or curved track: M1920.