68-pounder gun

Design

The cannon was designed in response to the need for heavier weaponry as armour on ships of the line improved. It was cast by the Low Moor Iron Works in Bradford in 1847 and entered service soon after. The cannon was relatively cheap to produce – the Royal Commission on the Defence of the United Kingdom estimated that each cannon cost approximately £167. (2010 : £12,645). Over 2000 were cast before 1861 and its exceptional durability, range and accuracy earned it a reputation as the finest smoothbore cannon ever made.

Operation

The gun was a traditional muzzleloader; it needed to be loaded from the front end of the barrel. Before it could be loaded the bore of the barrel was cleaned with a sponge, after which a propellant charge (gunpowder in a cloth bag) was rammed down into the breech. The gun was primed (using a metal spike inserted through the vent that pierced the charge), and fired using a percussion cap (which ignited the charge and forced the projectile out of the barrel). The estimated rate of fire of this weapon was between 55 and 70 seconds, though loading speed could be expected to fall off as crew became fatigued.

The 68-pounder had an effective range of approximately 3000 yd, however at its maximum elevation of 15 degrees it had a maximum range of 3620 yd, a distance that the projectile would cover in 15 seconds. the cannon fired a 68 lb solid shot at a muzzle velocity of 1579 ft/s.

The cannon could fire solid shot, explosive shells, grapeshot, case shot and "Martins Liquid Iron Shell" (thin walled shells filled with molten iron, intended to serve as heated shot). Although the cannon's barrel bore was 8.12 in, both shot and shells were 7.92 in in diameter. This allowed a windage gap of 0.1 in around the projectile; enough to aid the loading process, but not enough to seriously diffuse the propellant gasses.

The official weight of the shot was listed at 68 lbs but in reality this varied according to the material of the shot itself; cast iron shot weighed 67 lb, wrought iron shot and steel shot weighed 72 lb, and chilled steel weighed 68 lb. The explosive shells were primed with 4 lb of gunpowder. They were fitted with simple fuses that were ignited by the flash of the charge – early wooden fuses were eventually replaced by more reliable fuses designed by Captain Edward Boxer in 1849. The gun crew still had to gauge the best length of fuse for the range they were firing – ideally the shell should explode just before hitting its target. To prevent the shell exploding in the barrel it was fitted with a sabot to ensure the fuse faced away from the charge.

On land a minimum crew of nine men (usually commanded by a non-commissioned officer) was required to fire the gun, which was normally mounted on a traversing gun carriage.

Service

The cannon was put to use both on land and at sea. Several of these ships saw action during the Crimean War where the 68-pounder was used extensively during the Siege of Sevastopol. Along with 32-pounders and Lancaster guns they were taken from their ship mountings and dragged up to siege batteries by the Naval Brigade, from where they regularly bombarded Russian positions for the next year. The cannon was also fitted in large numbers to the Aetna-class ironclad floating batteries, although these had little impact on the war.

Most notably the 68-pounder was fitted to the s and . Originally it was intended to fit forty 68-pounders, primarily on one gun deck, but this specification changed during their building and they were finally equipped with twenty-six 68-pounders (13 on each side). Alongside these, the ships were equipped with new rifled breech loading Armstrong guns of two types; 7 inch and 40 pounders. Ironically the Armstrong Guns were therefore incapable of penetrating the armour fitted to the Warrior-class ships, while the 68-pounder (with its high muzzle velocity) could. As late as 1867 it was planned to fit the new s with 68-pounders, but they were instead completed with a RML 7 inch gun and a RML 64 pounder 64 cwt gun.

On land the 68-pounder was used extensively in British coastal defences constructed during the 1850s - notably at forts like Gomer and Elson defending Portsmouth, and Forts Victoria, Albert and Freshwater Redoubt defending the Needles Passage. The 1859 Royal Commission envisaged arming the numerous new forts they proposed with the 68-pounder cannon and costed for them accordingly. The introduction of the Armstrong gun initially led many to think that weapon would be used instead, but whilst the forts were being built, the Armstrong gun's weaknesses were exposed and the military reverted to using muzzle loaded weapons. However, the advantages of rifling and the Armstrong's wrought iron construction were retained, leading to a new design of artillery piece – rifled muzzle loaders.

Conversion to rifled muzzle loader

The introduction of rifled muzzle loaders (also classed as RMLs) rendered smoothbore guns largely obsolete. However, the 68-pounder and other smoothbores still existed in large numbers and various attempts were made to adapt the guns to fire new projectiles. Introduced in 1872, 68-pounders adapted in this way had a calibre of 6.29 in and were known as a RML 68-pounder, or officially as the RML 80-pounder 5 ton. With a 10 lb powder charge they could fire an 80 lb projectile at a muzzle velocity of 1240 ft/s. They were deployed as coast defence and garrison artillery around the British Empire and remained in service until eventually declared obsolete in 1921.

At least two 68 pounders were converted to 7 in 6.55 LT RML guns, firing a 115 lb or 150 lb double shot.

Surviving examples

• Southsea Castle
• Carrickfergus Castle
• Fort Nelson, Hampshire, Royal Amouries Collection
• Bradleys Head, Sydney Harbour, Australia
• Flagstaff Hill Fort, NSW, Australia
• Two guns at Port Fairy, Victoria, Australia - from Flickr
• Garden Island Dockyard, NSW, Sydney, Australia
• Halifax Citadel, Canada
• Daylesford Botanical Gardens, Victoria Australia.

Notes

References

Bibliography

• Treatise on the Construction and Manufacture of Ordnance in the British Service. Royal Gun Factory, 1877
• General Sir Howard Douglas, "A Treatise on Naval Gunnery". Fifth edition, revised. published by John Murray, London, 1860

References

1. Complete cost for 95 cwt gun including carriage, slide and appurtenances. Douglas, 1860, page 339
2. Treatise on Manufacture of Ordnance in the British Service, 1877, Table V page 72
3. Treatise on Manufacture of Ordnance in the British Service, 1877, Table VI page 73
4. "HMS Warrior - Armament". The Warrior Preservation Trust.
5. Hogg, p. 25
6. Lambert, p. 99
7. "Guns of the Crimean War". [[Royal Armouries]].
8. Lambert, p. 82
9. Cantwell, p. 21
10. This was followed by a projectile, often encased in wadding.Winton (1987), p. 30
11. Cantwell, p. 28
12. With a {{convert. 16. lb. kg
13. Lambert, p. 87
14. Holley, Alexander. (1865). "A Treatise on Ordnance and Armour". D Van Nostrand.
15. Cantwell, pp. 21, 28
16. Winton (2001), p. 112
17. Winton (1987), p. 6
18. Although the Armstrong guns represented a new direction in artillery, the breech loading mechanism meant that they were unable to withstand the explosion of a heavy cartridge. Smaller cartridge charges were therefore required and the gun's muzzle velocity suffered as a result.Hogg, p. 37
19. Cantwell, p. 31
20. Preston, Antony. (2007). "Send a Gunboat The Victorian Navy and Supremacy at Sea, 1854-1904". Conway Maritime.
21. "The Palmerston Forts Society - Fortlog data sheets".
22. Hogg, p.39
23. Hogg, p. 248
24. Owen, John Fletcher. (1879). "Treatise on Construction of Service Ordnance 1879". Harrison and Sons.
25. Hogg, p. 248
26. . ["7 inch 158 pounder Bow Chaser (Palliser Conversion)"](http://www.cerberus.com.au/armament4.html#bow_chasers).