4.7 inch Coast Gun

4.7 inch Coast Gun

The 4.7 inch Coast Gun entered service as a naval gun in 1887 and was adopted for land service in the 1890’s. By 1939 the various types and Marks had mostly disappeared leaving just the Marks 3, 3*, 4 and 4*. These were all 40 calibre guns differing only in minor details. The Marks 3 and 3* were built up steel guns and the 4 and 4* were steel and wire.

The breech mechanisms were conical, interrupted-screw blocks operated by a single motion lever. All the 4.7 inch Coast Gun mountings were of a central pivot type which differed only in small details. The largest change was in the Mark 3 which was taller so as to fire from behind a parapet.


B Mark 3Standard gun
B Mark 3*6 guns issued in 1901 with non-standard breech mechanism. Altered to
Mk 3 standard but retained nomenclature
B Mark 4Steel and wire 1892
B Mark 4*Slight difference in construction


Mark 1Central pivot, -10º to +20º. Trunnions 45.625 inches above emplacement floor
Mark 1*Mk 1 altered by fitting pistol grip replacing electric firing gear. Sight
illumimation added
Mark 1**Converted Naval Mk 2 to approximate Mk 1*
Mark 2Similar to Mk 1 but trunnions 41.75 inches above floor
Mark 3Similar to Mk1 but extra high pedastal carrying traverse rack. Trunnions
8 feet 9.625 inches above floor
Mark 3*Mk 3 mounting with Mk 4 cradle
Mark 4Similar to Mk 2 but -7º to +20º. Larger buffer cylinder. Trunnions
41.25 inches high
Mark 5*Mk 5 mounting (obsolete in 1936) with longer cradle than Mk 4 altered to
take Mk 4 gun


Marks 3 to 4* on Mountings Marks 1 to 4

Weight of Gun & Breech Mechanism4,592 lbs
Total Length194.1 inches (4,930 cm)
Length of Bore189 inches (40 calibres) (4,801 cm)
Rifling20 grooves, straight to 142.685 inches from muzzle
then increasing to 1/30 at muzzle
Breech mechanismInterrupted screw, electric & percussion fired
Elevation-10º to +20º Mks 1-3: -7º Mk 4
Recoil systemHydro-spring constant 8 inches
Weight in actionApprox. 6 tons with shield


Firing standard 45 lb Semi-AP shell
Muzzle velocity2,150 feet per second
Maximum Range11,800 yards


Shell, Semi-Armour Piercing Mark 3Semi because it could only deal with lighter armoured craft. Fitted with Base Percussion Fuze No. 501.
Propelling charge6 lb 4 oz of Cordite in straight taper brass case 15.9 inches long. Fitted with protruding adaptor for taking a Percussion or Electric Tube
The Royal Artillery 1939-45