.303 was a superior marksman's rifle, its components were machined to extremely fine tolerances which resulted in the weapon clogging too easily in the adverse environment imposed by trench warfare in the First World War. Additionally, British ammunition was too variable in its manufacturing tolerances to be used without careful selection, which was not possible in trench conditions. It was also possible for a careless user to disassemble the bolt for cleaning and then reassemble it with the bolt-head on back to front, resulting in a highly dangerous and sometimes fatal failure of the bolt to lock in the forward position on firing. Snipers, who were able to maintain their weapons carefully, and hand select and measure every round with which they were equipped, were able to use them to maximum effect and retained a considerable fondness for the weapon. Ross rifles were also used by Training units, 2nd and 3rd line units and Home Guard units in the Second World War and many weapons were shipped to Britain after Dunkirk in the face of serious shortages of small arms. Remington Model 1901 During World War I, the Royal Navy purchased 4,500 Remington Rolling Block rifles in 7mm Mauser from Remington's leftover stock after production had ended, issuing them to the crews of minesweepers and Q-ships. Rifle, Number 4 aka the Lee Enfield rifle Beginning shortly after the First World War, the SMLE went through a series of experimental changes that resulted in the Rifle, No. 4 Mk I, which was adopted in 1939 just after the beginning of the Second World War. The changes included receiver-mounted aperture rear sights, similar to that of the Pattern 1914 rifle and changed screw threads, making nearly all threaded components incompatible with those of the SMLE (No. 1) rifle. The No. 4 rifle had a heavier barrel, stronger steel in the action body and bolt body and a short "grip-less" (or "spike") bayonet that mounted directly to the barrel, rather than to a separate nose cap. The latter was the most prominent visual change. Later several models of bladed bayonets were created. During the Second World War, the British government also contracted with Canadian and US manufacturers (notably Small Arms Limited and Savage) to produce the No. 4 Mk I* rifle. US-manufactured rifles supplied under the Lend Lease program were marked US PROPERTY on the left side of the receiver. Canada's Small Arms