These were followed by a series of increasingly mammoth weapons—guns weighing , , , and finally , with calibre increasing from 8 inches (203 mm) to 16 inches (406 mm). The decision to retain muzzle-loaders until the 1880s has been criticised by historians. However, at least until the late 1870s, the British muzzle-loaders had superior performance in terms of both range and rate of fire than the French and Prussian breech-loaders, which suffered from the same problems as the first Armstrong guns. From 1875 onwards, the balance between breech- and muzzle-loading changed. Captain de Bange invented a method of reliably sealing a breech, adopted by the French in 1873. Just as compellingly, the growing size of naval guns and consequently, their ammunition, made muzzle-loading much more complicated. With guns of such size there was no prospect of hauling in the gun for reloading, or even reloading by hand, and complicated hydraulic systems were required for reloading the gun outside the turret without exposing the crew to enemy fire. In 1882, the 81-ton, 16-inch guns of fired only once every 11 minutes while bombarding Alexandria during the Urabi Revolt. The , 450 mm (17.72 inch) guns of the s could each fire a round every 15 minutes. In the Royal Navy, the switch to breech-loaders was finally made in 1879; as well as the significant advantages in terms of performance, opinion was swayed by an explosion on board caused by a gun being double-loaded, a problem which could only happen with a muzzle-loading gun. The calibre and weight of guns could only increase so far. The larger the gun, the slower it would be to load, the greater the stresses on the ship's hull, and the less the stability of the ship. The size of the gun peaked in the 1880s, with some of the heaviest calibres of gun ever used at sea. carried two 16.25-inch (413 mm) breech-loading guns, each weighing . A few years afterwards, the Italians used 450 mm (17.72 inch) muzzle-loading guns on the Duilio class ships. One consideration which became more acute was that even from the original Armstrong models, following the Crimean War, range and hitting power far exceeded simple accuracy, especially at sea where the slightest roll or pitch of the vessel as 'floating weapons-platform' could negate the advantage of rifling. American ordnance experts accordingly preferred smoothbore monsters whose round shot could at least