RBL 7 inch Armstrong gun

• Name — Ordnance RBL 7-inch gun • Origin — United Kingdom • Is Ranged — yes • Is Artillery — yes • Is Uk — yes • Service — 1861–190? • Used By — United Kingdom • Designer — W. G. Armstrong Co. • Production Date — 1859–1864 • Number — 959 • Unit Cost — £425–£650 (equivalent to £47000–£72000 in 2013) • Variants — 82cwt, 72cwt • Part Length — 99.5 in bore (14.21 calibres) • Cartridge — 90 to • Caliber — 7 in • Velocity — 1100 ft/s • Max Range — 3500 yd • Breech — Armstrong screw with vertical sliding vent-piece (block)

This method had already proved successful in the much smaller RBL 12 pounder 8 cwt field gun, and the British Government requested it be implemented for heavy guns despite Armstrong's protests that the mechanism was unsuited to heavy guns: Sir W. Armstrong to the Select Committee on Ordnance in 1863 • Illustration — A fibreglass replica aboard the museum ship HMS Warrior at Portsmouth, United Kingdom. Shells for the gun are on deck in the foreground. The gun as first made weighed 72 cwt (8,064 lb) but the heavier 82 cwt (9,184 lb) version, incorporating a strengthening coil over the powder chamber, was the first to enter service in 1861. It was intended to replace the smoothbore muzzle-loading 68-pounder gun, and was intended to be Britain's first modern rifled breech-loading naval gun. The lighter 72 cwt version eventually entered service in 1863 for land use only. The British government's Select Committee on Ordnance held lengthy hearings in 1862 and 1863 on the relative merits of the Armstrong breechloaders compared to other breechloaders and muzzle-loaders. It finally announced:... the preponderance of opinion seems to be against any breech-loading systems for the larger guns It was considered that with a maximum gunpowder propellant charge of only 12 pounds (soon reduced to 11 lb for the 82 cwt gun and 10 lb for the 72 cwt gun) the gun was incapable of a high enough muzzle velocity to penetrate the armour of enemy ships: Critics also considered that the manual labour needed to raise the heavy (136 lb) vent piece out of the breech before reloading was an unnecessary combat impediment. Another objection raised was that obturation (i.e. sealing of the breech on firing) depended on how tightly the gunners turned the breech screw after loading: Captain Blakely to the Select Committee on Ordnance As these limitations were imposed by the current Armstrong breechloading design, and as no other suitable breechloading mechanism was available, production of the 110-pounder was discontinued in 1864 and Britain reverted to muzzle-loading heavy guns. The remaining guns were moved to the role of fortress artillery where they remained in post for much of the Victorian era. The abandonment of the Armstrong breech-loading design led Britain to begin a major program of building rifled muzzle-loaders to equip its fleet. The Armstrong 110-pound gun was succeeded by various RML 7 and 8-inch guns. 7-inch Armstrong breech-loaders under construction at the time of cancellation were completed as RML 64-pounder muzzle-loaders. However, the gun construction method developed by Armstrong for breech-loaders, of a wrought-iron "A" tube surrounded by wrought-iron coils, was considered sound and was retained for the first generation of new rifled muzzle-loaders in the mid-1860s. When Britain returned to breech-loaders in 1880 it used the Elswick cup and the French De Bange obturation systems, both of which used the power of the gun's firing to achieve obturation rather than manual labour.

• Illustration — An Armstrong 7 in rifled breechloader in the 19th century. The gun was used extensively by Royal Navy ships against land fortifications in the Bombardment of Kagoshima and Bombardment of Shimonoseki in 1863 and 1864. We have two descriptions of the same incident aboard Euryalus at the Bombardment of Kagoshima in August 1863: Letter from an officer of HMS Euryalus to historian William Laird Clowes many years after the event. An officer from HMS Euryalus, published in The Times on 25 April 1864. The guns, while functioning well when correctly handled, were hence seen to be difficult and potentially dangerous to use under the stress of combat. During the New Zealand Wars, the gun was used in the bombardment of the Maori fortifications at Gate Pa on 29 April 1864. Although subjected to one of the fiercest bombardments of the wars, the Maori defenders were protected by anti-artillery bunkers and went on to repel the British force, inflicting heavy casualties.

• Illustration — Diagrams showing projectiles Mark II common shell, Mark I segment shell, Mark V case shot • Illustration — Powder cartridge with lubricator on top • Illustration — The lead-coated shell used by the gun

• Illustration — RBL 7-inch Armstrong gun in Fort No 1, Lévis, Quebec, Canada • An 82cwt gun at Victoria Barracks, Sydney • An 82cwt gun at Saint Helier, Jersey • A 72cwt gun at Fort Nelson, Portsmouth, UK. It is fitted with a replica breech and carriage. • At Fort Henry, Ontario, Canada • A 72 cwt gun at Quebec Citadel, Canada • A 72 cwt gun at Fort No. 1, Lévis, Quebec