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12 inch Railway Howitzer

A WW1 gun, some Mk3 & Mk5 guns were stored after the war and reappeared in 1939. Some of these went to France in 1939 and were left behind in 1940. The German's took them on strength but don't appear to have used them. Those still in England were deployed in possible invasion areas as a mobile reserve. They were declared obsolete in Aug 1945.

Gun

Mk 3 - Elswick design
Mk 3A - 1940 replacement for Mk 3. Doubtful if any were built
Mk 5 - Similar to Mk 3 but with less weight at the muzzle
Mk 5A - 1940 replacement for Mk 5. Loose liner
Mk 6 - 1940 replacement for Mk 3A. Simpler and lighter for easier construction

Mounting

Mk 2 - Barbette mounting. Anchored by steel cables
Mk 3 - Higher mounting with loading platform. Four removeable outriggers

Data

Howitzer Mk 3 on Mounting Mk 2
Weight gun & breech - 25,221 lbs
Wt in action - 170,143 lbs
Length - 225.3 inches
Length of bore - 207.6 inches
Rifling - 60 grooves uniform RH 1/15
Breech mech - Interrupted screw, continuous motion, percussion fired
Elevation - 0º to plus 65º
Traverse - only to be fired 20º R & L of centre line
Recoil system - Hydropneumatic constant
Recoil length - 60 inches

Performance

With 750 lb HE shell:
Muzzle velocity - 1,468 ft/sec
Max range - 14,350 yds

Ammunition

Shell HE Mk 10 - Nose fuzed non streamline
Shell Common Pointed Mk 1A - Base Percussion Fuze for hard targets
Shell Concrete Piercing Mk 1 - Never entered service
Propelling Charge
Short Range Portion - Charges 1 to 6
Long Range Portion - Charges 7 to 11