They fired a projectile weighing approximately 9 pounds (4.1 kg).

The 9-pounder 8 cwt Rifled Muzzle Loader was the field gun selected by the Royal Artillery in 1871 to replace the more sophisticated RBL 12 pounder 8 cwt Armstrong gun, which had acquired a reputation for unreliability.

[2] The gun was rifled using the system developed by William Palliser, in which studs protruding from the side of the shell engaged with three spiral grooves in the barrel.

[2] The 9-pounder remained in front-line service with the Royal Artillery until 1878 when the RML 13 pounder 8 cwt gun was introduced.

[4] A number were issued to British Artillery Volunteer units, with the 1st Ayrshire and Galloway Artillery Volunteers being issued with some guns as late as 1901.