An Armstrong gun was a uniquely designed type of rifled breech-loading field and heavy gun designed by Sir William Armstrong and manufactured in England beginning in 1855 by the Elswick Ordnance Company and the Royal Arsenal at Woolwich. Such guns involved a built-up gun construction system of a wrought-iron (later of mild steel) tube surrounded by a number of wrought-iron strengthening coils shrunk over the inner tube to keep it under compression.