RML 64-pounder 64 cwt gun
The RML 64-pounder 64 cwt gun was a Rifled, Muzzle Loading (RML) naval, field or fortification artillery gun manufactured in England in the 19th century, which fired a projectile weighing approximately . "64 cwt" refers to the gun's weight rounded up to differentiate it from other "64-pounder" guns. Description. The calibre of 6.3 inches was chosen to enable it to fire remaining stocks of spherical shells originally made for the obsolete 32 pounder guns if necessary. Mark I (adopted in 1864) and Mark II (adopted 1866) guns, and Mark III guns made  from 1867 – April 1871 had wrought-iron inner "A" tubes surrounded by wrought-iron coils. Mark III guns made after April 1871 were built with toughened mild steel "A" tubes, and earlier Mark III guns were re-tubed with steel and were classified as a siege gun in land service. Remaining guns with iron tubes were used for sea service. Rifling of all guns consisted of 3 grooves, with a uniform twist of 1 turn in 40 calibres (i.e. 1 turn in 252 inches). Ammunition. The gun's standard shell was "common shell", for firing on troops in cover, ships  and buildings, weighed when empty with a bursting charge of . Shrapnel shells could also be fired; a shell with a bursting charge propelling 234 metal balls.