Not enamored of that new fangled steel stuff, but found this
https://www.britishempire.co.uk/forces/armyarmaments/rifles/sniderhistory.htm"As early as 4 March 1867, the Superintendent of the Royal Small Arms Factory had reported very favorably on five-grooved steel barrels in conjunction with the Snider breech. All barrels of the new pattern Sniders were stamped STEEL on the left-hand side, just below the backsight..."
Could not find the composition of that steel though it was likely open hearth 'mild steel' (AISI 1008 - 1020) invented by Siemens about 1860
I found a statement that the 1862 Snider Enfield barrels were wrought iron.
