Introduced into service in 1871 and 1873. It consists of two parts—a toughened steel tube, and a jacket composed of two single coils and a trunnion-ring welded together. The cascabel is cut out of the solid end of the steel tube, and is recessed to receive the head of the elevating screw, which is fastened to it by a bolt and keep-pin. The 6 cwt. and 8 cwt. guns differ only in length and weight, the latter being 10½ inches longer. The 7-pdr. and the 9-pdr. are of the same calibre, but the same projectiles cannot be used in both, as the twist is different and the studs on the 7-pdr. projectile are much wider than those of the 9-pdr. The arrangement of the sights is the same for both guns. It is easily distinguished by the abrupt step at the forward end of the jacket. [Illustration: 9-pdr.] _64-pdr. Wrought Iron R. M. L. 64 cwt._ There are three marks or patterns of this gun. Mark I. was adopted in 1864 to replace the Armstrong wedge breech-loaders. It belongs to the Armstrong type of construction, and consists of a wrought-iron coiled A tube, a forged breech-piece, a trunnion-ring, several outer coiled tubes, and a muzzle-ring. The A tube being bored all the way through, the joints at the bottom of the bore were closed by means of a heavy copper gas-check. The calibre is 6.3 inches, in order to permit firing 32-pdr. round shot from it. The greater part of these guns have been retubed with a steel A tube. In these, the plain groove is found, whilst the iron-tubed ones have the shunt groove. This gun is easily recognizable by its raised trunnion-ring and also by the combination of the stepped breech with the muzzle-ring. Mark II. was adopted in 1866. It is made up of a coiled wrought-iron A tube, double at the chase, a forged breech-piece, a breech-coil composed of a double coil and trunnion-hoop welded together, a coil in front of the trunnions, and a cascabel block. The end of the bore of the A tube is reduced and forms a gomer chamber. These guns may be recognized either by the shunt rifling combined with the Woolwich form of gun or by the letter B marked on the left trunnion. Mark III. is made up of a solid-ended steel A tube, a breech-coil made up of a triple coil, trunnion-ring and coil in front of the trunnions welded together, and a forged cascabel block. These guns are similar in appearance to the 7-inch, but the sea-service guns of this mark have iron A tubes, and may be recognized by the shunt rifling. _64-pdr. R. M. L. 71 cwt. (Converted.)_ [Illustration: 64-pdr. Converted.] Adopted in 1864. This gun is the old cast-iron 8-inch gun, which is bored out and tubed on the Palliser plan. The tube is coiled and double at the rear, and, being through bored, the bottom joints are closed by a screw cup. After insertion the tube is held in place by a muzzle screw-collar and a pin tapped through the casing just forward of the trunnions. The gun is easily recognized from its old-fashioned shape. _7-inch R. M. L. 6½ tons and 90 cwt._