9.2 inch Gun

9.2 inch Gun

The 9.2 inch Gun was the premier coast defence gun in the 1880’s and remained so until Coast Defence disolved in 1956. There had been many variations of the gun, mostly in naval service but during WW2 only the Marks 9 & 10 were in use. The Mark 9 entered service in 1896 and was modernised in 1910 by fitting a single motion breech mechanism. This became the C Mark 9. The Mark 10 was introduced in 1899 with similar performance to the Mark 9 but had a slightly different breech mechanism with a Welin screw block. The Mark 10 had a slightly higher rate of fire.

The mountings were all the barbette type. The gun was emplaced in a pit with the barrel just clearing a parapet. A steel plate platform surrounded the gun forming a roof over the pit, which held the lower part of the mounting. Below this roof, ammunition was brought into the pit from underground magazines. By means of lifts and a trolley riding on a rail suspended from the roof, the round was delivered to a point below the breech. A lever opened a trapdoor in the roof and an hydraulic lift raised the shell to the breech. After the shell was rammed the same procedure was carried out to deliver the bag charge. The lift lowered and the trapdoor was closed before the gun fired.


Mark 9Basic design, obsolete July 1941
C Mark 9Converted to single motion breech mechanism
Mark 10Different breech mechanism to Mk 9 – Welin screw block
Mark 10VGuns Nos. 240 & 241 designed by Vickers & differing in minor
construction details
Mark 10*The inner “A” tube tapered to ease withdrawl
Mark 15Approved April 1940. A Mk 10 with Asbury breech mechanism & built up gun


Mark 5As described above. Elevation -10º to +15º, maximum range 21,000 yards
Mark 5AModified to take a C Mk 9 gun. Installed at Rock Bty, Gibraltar & New
Needles Bty, Isle of Wight, probably nowhere else
Mark 5BSimilar to Mk 5A but changes in loading arrangements to suit
improved projectiles introduced 1911-13
Mark 5CInstalled on non-standard pedestal (No.4 instead of No.7). Only installed
South Foreland Bty, Dover 1941
Mark 6As for Mk 5 but max elevation 30º. Shields increased in height, of armour
steel. Trolley moved to floor of the pit
Mark 6AConversion of Mk 5 to increase elevation to 30º, maximum range
29,500 yards. Hand traverse & ramming, power elevation
Mark 7Developed in the late 1920’s. As for Mk 5 but -5º to +35º elevation. Had
rapid-loading gear, hydraulic wash-out & rammer, powered
elevation & traverse.
Mark 8Vickers design for twin gun mount. Drawings produced in 1940 but no
further action taken
Mark 9A 1939 simplified version of Mk 7. Rammer changed to rigid chain. Hoist
now carried the shell & 2 portions of the charge. Doubtful many were built


9.2 inch Gun Mark 10 on Mounting Mark 7

Weight of Gun & Breech Mechanism62,720 lbs
Total length442.35 inches
Length of Bore429.33 inches (46.7 calibres)
Rifling37 grooves, straight to 303.585 inches from muzzle
then increasing to 1/30 at muzzle
Breech mechanismWelin screw, single motion electric or
percussion fired
Elevation-5º to +35º
Recoil systemHydropneumatic , constant 40 inches
Weight in actionApproximately 125 tons
Rate of Fire2 – 3 rounds per minute


Firing standard 380 lbs HE Shell

Muzzle velocity2,700 feet per second
Maximum range36,700 yards


Shell, HE Mark 19BConventional nose-fuzed with Lyddite filling. Fitted with
Percussion Fuze No. 45P
Shell, APC Mark 15BCapped piercing shell with Percussion Base Fuze No. 346
Shell, CPC Mark 9ACapped piercing shell with Percussion Base Fuze No. 15 for
ightly protected vessels
Shell, Shrapnel Mark 10 AFilled with 2,500 lead/antimony balls & 2 lbs gunpowder
expelling charge. Mostly used in practice & obsolete
during the war
Propelling chargeTwo half charge bags each of 53½ lbs of Cordite in a
silk cloth bag with gunpowder igniter in the rear end.
Two units made a full charge but ½ charges could be
fired in practice shoots
The Royal Artillery 1939-45