RBL 40 pounder Armstrong gun

The Armstrong RBL 40 pounder gun was an early attempt to use William Armstrong's new and innovative breechloading mechanism for medium artillery.

Design history
The Armstrong "screw" breech had already proved successful in the RBL 12 pounder 8 cwt field gun, and the British Government requested it be implemented for heavier guns despite Armstrong's protests that the mechanism was unsuited to heavy guns.

The first version weighed 32 cwt, followed by the 35 cwt version which introduced a longer and stronger breech-piece.

Variants
A 32 cwt variant having a horizontal sliding wedge breech instead of the Armstrong screw with vertical vent-piece was introduced in 1864 as an attempt to address the perceived weaknesses of the screw-breech design. It was withdrawn from service by 1877.

From 1880 a small number of 35 cwt guns had their trunnion rings rotated to the left to allow the vent-piece to open horizontally to the right, being known as "side-closing" guns. They differed from the wedge guns in that the vent piece was still locked in place by tightening the screw behind it.

Naval service
The gun was recommended in 1859 for the Navy as a broadside or pivot gun.

An officer from HMS Euryalus described the gun's performance at the Bombardment of Kagoshima of August 1863: The 40-pounder we found answer exceedingly well, for coming out of the place [Kagoshima] we planted common shell, with pillar fuze, wherever we wished, at a range of 3,800 yards. Three steel vent-pieces broke, but another placed them immediately and no harm was done. These guns work very easily, are very true, and the drill is very simple.

British Service
The guns were typically employed mounted on high "siege travelling carriages" for use as semi-mobile guns in forts, firing over parapets. Many were mounted on travelling carriages and used by many Volunteer Artillery Batteries to whom they were issued after 1889. Most remained in use in this role until 1902. A number were used for some years afterwards as saluting guns.

Colony of Victoria service
The Australian colony of Victoria received six 35 cwt guns in August 1865. They were used as mobile coast fortification guns with one gun being fitted to the colonial sloop Victoria during 1866 & 1867. Later four of the guns were used as field guns at Hastings. Three of these guns are known to survive.

Colony of Tasmania service
As a result of the Jervois-Scratchley reports of 1877 into the defence of Australian colonies following the withdrawal of British troops, the Launceston Volunteer Artillery Corps in Tasmania acquired 2 guns on late-model iron carriages with iron wheels, which they continued to operate until at least 1902.

Surviving examples

 * A gun made by Royal Gun Factory in 1865 at Elizabeth Castle, Jersey
 * Restored gun No. 272 at Hastings-Western Port Historical Society Museum, Victoria, Australia
 * Restored Gun No. 271 at Fort Queenscliff, Victoria, Australia
 * Unrestored Gun No. 268 in Como Park, South Yarra, Victoria
 * A gun at Fort Henry, Canada
 * A 40-pounder horizontal-wedge gun at Royal Armouries, Fort Nelson, Portsmouth
 * On board HMS Warrior, Portsmouth, UK