the breech-block merely needing to lock the cartridge case in place. This was more easily accomplished by sliding the block in behind the cartridge case through a vertical or horizontal slot cut through the rear of the breech : the "sliding wedge" or "sliding block" breech. History Early breechloaders The very first cannons of the Middle Ages were breech loaded, with gunpowder and shot contained in pots dropped at the back of the barrel, but the poor seals made them dangerous, and they wore quickly and could not be scaled to larger weapons. Until the 19th century, only muzzle-loaders were used. In 1837 Martin von Wahrendorff patented a design for a breech-loader with a cylindrical breech plug secured by a horizontal wedge; it was adopted by Sweden in 1854. Independently, Giovanni Cavalli first proposed a breech-loader gun in 1832 to the Sardinian Army, and first tested such a gun in 1845. Armstrong screw breech Advances in metallurgy in the industrial era allowed for the construction of rifled breech-loading guns that could fire at a much greater muzzle velocity. After the British artillery was shown up in the Crimean War as having barely changed since the Napoleonic Wars the industrialist William Armstrong was awarded a contract by the government to design a new piece of artillery. Production started in 1855 at the Elswick Ordnance Company and the Royal Arsenal at Woolwich. His "Armstrong screw" breech involved loading the shell and gunpowder propellant charge in a cloth bag through the hollow breech screw, lowering a heavy block into a slot behind the powder chamber and screwing the breech screw tightly against the block to lock it in place. A degree of obturation was achieved via a cup on the face of the block being forced into a recessed ring on the chamber face. The system was in effect a vertical sliding block such as later used by Krupp in both horizontal and vertical form, with the crucial difference that Armstrong failed to make the progression to loading the powder charge in a metal cartridge, with the result that complete obturation was impossible. Whatever obturation that was achieved relied on manual labour rather than the power of the gun's firing, and was hence both uncertain, based on an unsound principle and unsuited to large guns. Armstrong screw-breech guns were initially adopted by the British Army and Royal Navy, but concerns about limited armour