The Long Land Pattern musket and its derivatives, all 0.75 inch calibre flintlock muskets, were the standard long guns of the British Empire's land forces from 1722 until 1838, when they were superseded by a percussion cap smoothbore musket. The British Ordnance System converted many flintlocks into the new percussion system known as the Pattern 1839 Musket. A fire in 1841 at the Tower of London destroyed many muskets before they could be converted. Still, the Brown Bess saw service until the middle of the nineteenth century.