RBL 20 pounder Armstrong gun

The Armstrong Breech Loading 20 pounder gun, later known as RBL 20 pounder, was an early modern 3.75 inch rifled breech-loading light gun of 1859.

History
The gun was effectively a larger version of the successful RBL 12 pounder 8 cwt Armstrong gun. There were different versions for Land and Sea service.

Sea service


The RBL 20 pounder of 13 cwt and 15 cwt for sea service was introduced in 1859. It is 2½ feet shorter than the land version giving it a bore of only 54 inches (14.43 calibres), and hence a short stubby appearance. Its short barrel only allowed it to attain a muzzle velocity of 1,000 ft/second.

The 15 cwt gun, identifiable by the raised coil in front of the vent slot, was intended for broadside use in sloops. The more lightly constructed 13 cwt gun was known as a pinnace gun and was intended for boat use.

Land service
The RBL 20 pounder of 16 cwt for land service was introduced in 1860. It has a bore of 84 inches (22.36 calibres) and hence has the appearance of a typical field gun.

Surviving examples

 * An unrestored 13 cwt pinnace gun at Hong Kong Museum of Coastal Defence
 * A 16 cwt gun on board HMS Warrior at Portsmouth, UK
 * A 13 cwt gun dated 1859 at the Artillery Museum, North Head, Sydney, Australia