The Armstrong Breech Loading 12 pounder 8 cwt was a field gun designed by the manufacturing company W.G. Armstrong Co. in 1859. The Armstong 12lber (later known as the RBL 12 pounder 8 cwt) was one of the earliest examples of a rifled, breech loaded field gun.
The Armstrong 12lber was well ahead of its time for the era in which it was made. The concept of breech loading (whereby the user(s) would load the cannon from the rear of the cannon rather than from the muzzle) had only just begun to emerge in the rifles and muskets of the era (for example the Dreyse Needle Gun from 1841). Likewise rifling was a relatively new concept, both of which were combined to make the Armstrong 12lber, perhaps, the most potent cannon of its time.
The rifling relied upon the shell (coated in lead) to engage with the grooves cut into the inner surface of the barrel, producing a spin on the shell, giving it greater accuracy and range. The lead coat would deform, completely filling the barrel to engage with the rifling. This deformation would also improve the efficiency of the Armstrong 12lber in terms of powder, as there was no room around the shell for the gas to escape unless it pushed the shell forward, meaning that the total amount of powder needed to propel the shell was halved.
The barrel was constructed of layers of wrought iron tubes, which were heated up and cooled around each other. This process, which meant that the barrel was "pre-stressed", greatly improved the strength of the Armstrong 12lber (at the same time making it lighter than other conventional field guns) as the inner layers of the barrel were under pressure from the layers around it, preventing them from stretching. This method was also more efficient interms of the amount of material used.
The Armstrong 12lber was given a caliber of 3in (76.2mm), meaning that it would accept the lead coated "Common Shell" that was effectively the British standard issue artillery shell at the time (as the cannon ball was phased out). Other shells used with the Armstrong 12lber were a lighter (10lb 11oz) Shrapnel shell and a (10lb 8oz) Segment shell.
The Armstrong Breech Loading 12 pounder 8 cwt became the first rifled cannon/artillery piece in the British Army in 1859. In its time the Armstrong 12lber would be modified by the Royal Navy and also see action in the New Zealand Land Wars and be used during the Second Opium War.
The British Army took the Armstrong 12lber as the standard field gun almost immediately in its original length of 84in. However, despite the vast improvements that the Armstrong 12lber had been incorporated with technologically, its high maintainence and high cost (sold to the army at between £79-£170) meant that the British army would revert to cheaper, easier to maintain muzzle loaders just 12 years later.
Meanwhile the Royal Navy obtained their own Armstrong 12lbers, however their versions were shortened to 72in in length, achieved by cutting a length of 12in off of the barrel to allow them to be more user friendly (and space friendly) aboard the Ships-of-the-Line. This version would be deployed both on land and on sea.
Colony of Victoria
The Colony of Victoria bought 6 examples of the Armstrong 12lber in 1864 (one of which is on display (pictured) in the Australian War Memorial in Canberra) for their horse artillery. Earlier the Colony of Victoria had sold 6 Armstong 12lbers to New Zealand for a total value of 3,592 pounds 1s 8d. These guns would be used to fight the Maori tribes.
New Zealand Land Wars
New Zealand had begun aquiring cannon and artillery pieces to fight against the Maori in the New Zealand Land Wars. Numerous battles featured the Armstrong 12lbers until New Zealand aquired larger 24lbers of unknown origin. After the war these cannon were kept in Auckland to arm the militia.