The decks and hull sides were strengthened to carry the planned armament, and to absorb the force when the guns were fired.

On the completion of her conversion on 20 August 1864, she was the first British turret-armed ship, and the only one with a wooden hull.

[1] The initial guns carried were 10+1⁄2-inch (270 mm) smoothbores that fired a 150-pound spherical steel shot.

On 15 January 1866 three shots were fired at close range against the after turret of Royal Sovereign by one of the 9-inch (230 mm) guns carried by HMS Bellerophon to evaluate how well Coles' turrets held up to gunfire.

She was thereafter attached to the naval gunnery school HMS Excellent as gunnery ship until 1873, when she was replaced by HMS Glatton and demoted to fourth class reserve.