RBL 20 pounder Armstrong gun

RBL 20 pounder gun
16 cwt field gun with limber
Type	Naval gun Field gun
Place of origin	United Kingdom
Service history
In service	1859 - 19??
Used by	British Empire
Production history
Designer	W.G. Armstrong Co.
No. built	412
Variants	13, 15 and 16 cwt
Specifications
Weight	Naval : 13 long hundredweight (660 kg) or 15 long hundredweight (760 kg) Field : 16 long hundredweight (810 kg)
Barrel length	Naval : 54 inches (1.372 m) Field : 84 inches (2.134 m) bore & chamber
Shell	21 pounds 13 ounces (9.894 kg)
Calibre	3.75-inch (95.2 mm)
Breech	Armstrong screw with vertical sliding vent-piece (block)
Muzzle velocity	Naval : 1,000 feet per second (300 m/s) Field : 1,130 feet per second (340 m/s)
Effective firing range	3,400 yards (3,100 m)

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.

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.

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.

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.