Armament and armour for a coastal ironclad

New Ironsides carried fourteen 11-inch Dahlgren smoothbores, two 50-pounder Parrott rifles, and two 50-pounder Dahlgren rifles. The 11-inch weapons replaced a less satisfactory 9-inch choice. Protection included a four-and-a-half-inch belt and battery, a one-inch armoured deck, and two-and-a-half-inch armoured bulkheads. HMS Warrior carried forty guns and was a much larger ship intended for global service, so a simple battery comparison favours the British design. New Ironsides remained a formidable American frigate whose guns and protection suited coastal war. In a hypothetical Anglo-American fight, an estimated British numerical advantage of five or six ships to one would matter at least as much as either ship's individual qualities.