Armstrong BL gun, post-1858

Ordnance abbreviations:
BL = Breech Loading (either rifled or smooth bored)
RBL = Rifled Breech Loading
RML = Rifled Muzzle Loading

From 1858, Armstrong Guns are all rifled - some were Muzzle Loaded others were Breech Loaded. A gun prefixed by Armstrong after 1858 will be rifled as no Armstrong Guns from 1858 were smooth bored.
Some  guns made from c1350 were breech loaded smooth bores, but most were muzzle loaded smooth bored. Armstrong introduced Rifling to Cannon in 1858.
The guns should be described as Armstrong RBL Gun or Armstrong RML Gun but most Historians, when talking about post-1858 Armstrong Guns, assume that everyone knows they were rifled so they are only identified as BL or ML.
John Osborne replies to an enquiry - thanks, John.