RML 64 pounder 71 cwt gun

The RML 64 pounder 71 cwt guns (converted) were rifled muzzle-loading guns converted from obsolete smoothbore 8-inch 65 cwt shell guns. "71 cwt" refers to the gun's weight rounded up to differentiate it from other "64-pounder" guns : 1 cwt = 112 pounds.

Design
When Britain adopted rifled ordnance in the 1860s it still had large stocks of serviceable but now obsolete smoothbore guns. Gun barrels were expensive to manufacture, so the best and most recent models were selected for conversion to rifled guns, for use as second-line ordnance, using a technique designed by William Palliser. The Palliser conversion was based on what was accepted as a sound principle that the strongest material in the barrel construction should be innermost, and hence a new tube of stronger wrought iron was inserted in the old cast iron barrel, rather than attempting to reinforce the old barrel from the outside.

This gun was based on the cast-iron barrel of the 8 inch 65 cwt gun, which previously fired a shell weighing 50 pounds. The 8-inch gun was bored out to 10.5 inches and a new built-up wrought iron inner tube with inner diameter of 6.29 inches was inserted and fastened in place. The gun was then rifled with 3 grooves, with a uniform twist of 1 turn in 40 calibres (i.e. 1 turn in 252 inches), and proof fired. The proof firing also served to expand the new tube slightly and ensure a tight fit in the old iron tube.

Deployment
This gun was deployed on many smaller British cruising warships around the world, and also as a coast defence gun in British colonial garrisons.

Surviving examples

 * Dartmouth Old Battery, Devon, UK
 * A gun from 1872 at Southsea Castle, UK
 * No. 142 of 1869 at St Helier, Jersey
 * 2 guns, No. 398 and 407 at the Royal Australian Artillery Memorial, Mount Pleasant, Canberra, Australia
 * A gun at Mays Hill Cemetery, Parramatta, New South Wales, Australia
 * A gun outside the wardroom at HMNZS Philomel, Auckland, New Zealand
 * A gun on a locally-made carriage at Army Memorial Museum, Waiouru, New Zealand