These gun barrels, now displayed at Fort Siloso, were found buried near the Woolwich Loop on Blakang Mati. Given the location’s proximity to Fort Connaught, it is almost certain that these are the two Mark IVs once mounted at that Fort. The 8 Inch barrel is probably from Mount Serapong.
The 9·2 Inch BL gun was produced in response to the German Krupp 24cm gun of 1879. That gun could penetrate 20 inches (50.8 cm) of wrought iron. Construction of the 9·2-inch gun gained approval in 1880. The somewhat odd calibre of 9.2-inches (23.37 cm) was said to have been decided on so that the projectile (shell) could weigh an even 380lbs (172.4 kg). The 9·2 Inch gun became the standard British heavy coast artillery gun.
One Mark IV Gun on a Mark I Mounting was a emplaced at Fort Siloso from about 1890 to 1908/09. The location of the gun was to the left where the replica 6 Inch BL gun is today. Two more guns were emplaced at Fort Connaught, and two at Fort Pasir Panjang.
The gun was rifled and breech loading. It was constructed from steel and weighed 23 tons (23,369 kg). The construction was an inner rifled tube, the ‘A’ Tube onto which was shrunk the breech piece. Over the ‘A’ Tube was shrunk six steel hoops. The gun had Mark III Tangent Sights for aiming. The breech was operated by a Cam Lever. It took several movements to open and close the breech. The gun was mounted on a Sliding Carriage behind a 7 foot (2.13 m) parapet. It could depress to an angle of 5°, and elevate to 15°. A Derrick was used to load ammunition. The Gun Carriage allowed a recoil of 52 inches (132 cm). It had an arc of fire of 180°. The gun was elevated by means of a hand wheel. Traversing gear was on both sides of the Carriage Slide.
The gun had a range of 11,400 yards (10,424 m). It could penetrate a little over 18 inches (45.7 cm) of wrought iron at a range of 1,000 yards (914 m).
The ammunition supply came from a magazine below the gun. Two hoists were used to raise ammunition, one for propellant cartridges and one for projectiles.
The propellant charge was 41lb (18.6kg) of Brown Prismatic Powder. This was an improved Black Powder formed into prismatic shapes such as hexagonal or octagonal. These charges had a primer of black powder at one end to aid ignition. Later, cordite was used on these guns. The cordite coming in half-charges of 26 lb 12 oz (12.13 kg). These had a primer of R.L.G. powder. The cartridges were encased in silk, and packed in zinc cylinders. A Firing Tube was inserted in the breech to ignite the propellant charge.
The projectiles weighed 380lbs (172.4kg), and were Common Shell, Common Pointed Shell, Shrapnel and Armour Piercing (A.P.). The gun at Siloso will have had Armour Piercing and probably Common Shell. The length of the shells varied slightly from type to type. The bursting charge in an A.P. shell was an 18 lbs (8.16 kg) mixture of F.G. and P. powder.
The gun detachment consisted of eleven men, the Gun Captain, Gun Layer and nine other men. Their duties were:-
Gun Captain. In command.
Gun Layer. Firing Tubes. Sighting the gun.
No.2. Rammer and sponge, and scraper. Loading Trays
No.3 Traversing handles.
No.4. Elevating wheel and assists the No.2.
No.5. Winch handle.
No.s 6 & 9. Bucket filled with water, and sponge cloth
No.s 7 & 8. Transporting barrow. Fuzes.
No.10. Assists 2 and 4 with Loading Trays.
Additional men would be in the magazine below, moving shells and propellant cartridges to the ammunition hoists.
The rate of fire was about one round every two minutes.