These guns were the first to incorporate the new "Woolwich"
rifling system, a modification of the French system, of from 3 – 9 broad shallow grooves after Britain abandoned the Armstrong "shunt" rifling system in May 1865 : "...M.L. guns in course of manufacture were rifled on this principle, upon which all of our heavy pieces since have been rifled. The referred to, and introduced into the service in 1865, were the first of the so-called Woolwich guns, which then meant "''wrought iron M.L. guns built up on Sir W. Armstrong's principle, improved upon by hooking the coils over one another, and having solid ended steel barrels, rifled on the system shown above, for studded projectiles''". All versions were constructed of a steel A tube surrounded by various numbers and thicknesses of
wrought-iron coils. Rifling was 3 grooves with a uniform 1 turn in 35 calibres i.e. in . Some sources credit these weapons with the ability to pierce up to of armour. The following warships were armed with the gun : • s in commission from 1865 • commissioned in 1866 • commissioned 1866 • commissioned 1866 • s commissioned 1867 • s in commission from 1867 • s (as re-gunned in 1867) • & (as re-gunned in 1868) • s (as re-gunned in 1867–1868) • s (from 1868) • (as re-gunned in 1868) • in commission from 1869 • in commission from 1876 •
Briton-class screw corvettes in commission from 1871
RML 7-inch 90 cwt gun This was a lighter (90
cwt = 4½
tons) low-powered naval gun introduced in 1874 as a broadside gun on unarmoured vessels, and not intended for attacking armour plate. Early models were made by simply turning off some of the jacket around 6½ ton guns, as firing with reduced charges placed less strain on the coils. Some new guns were made to similar design. The following warships were armed with the gun : • s in commission from 1874 • in commission from 1874 • s in commission from 1874 • s in commission from 1877 • s in commission from 1877 == Ammunition ==