It should be pointed out that the twist is 1-10 Left hand concentric. Just a little trivia.
Rifle No. 4, MARK 1:
Adopted in November 1939. This rifle was the main British service rifle in WWII. Simplified for manufacture, the No. 4 has the heavy barrel, smaller bolt head, rear sight mounted on the receiver bridge, lightened nose cap, projecting barrel with lugs for spike type bayonet and front sight mounted on heavy band with protecting ears, similar to the Mark IV. The receiver is stronger and heavier that of the No 1's. The No 4 Mark 1 has been made with four different patterns of rear sights varying from finely machined adjustable leaf to "L" types and six patterns of bayonets are usable on the weapon. This rifle was made by B.S.A., Maltby, and Fazakerly. B.S.A. production of this rifle wand the No. 4 Mark 1 (T) was over 1,000,000 from 1940 to 1945. The No 4 Mark 1 was also made for sometime at the Stevens Arms branch of Savage Arms Corp. at Chicopee Falls, Mass., and Long Branch before production of the No 4 Mark 1*