The L42A1 was a British Army, Royal Marines and RAF Regiment sniper rifle chambered for the 7.62mm NATO cartridge which entered service in 1970. The rifle served until replaced by the Accuracy International L96 in 1985. The L42A1 was the last model in a long and distinguished line of Lee bolt-action rifles utilizing the rear-locking action designed by James Paris Lee for the British Army, which first entered service in the Lee–Metford rifle of 1888. During its British Army service, the L42A1 saw active service during several conflicts including the Dhofar Rebellion in Oman, The Troubles in Northern Ireland, the Falklands War and Gulf War.
Design details

The L42A1 was a 7.62×51mm NATO conversion of the .303 British chambered Lee–Enfield No. 4 Mk1(T) and No. 4 Mk1*(T) WWII-era British sniper rifles, which had remained in service for some time after the L1A1 variant of the 7.62mm FN FAL replaced the No.4 Lee–Enfield as the standard service rifle in 1957. It differed from other post-war No4 based variants in that the trigger remained hinged on the trigger guard as on the No4 Mk1 and 1*, not hung from the receiver as in the later No4 Mk 2, Mk 1/2 and Mk 1/3 .303 British rifles, and other 7.62×51mm NATO conversions. The conversion programme was carried out at Royal Small Arms Factory Enfield from 1970 to 1971. About 1,080 rifles were converted. A new hammer-forged heavy 7.62×51mm NATO barrel was installed, with four-groove, right hand twist rifling instead of the five-groove left-hand Enfield-type rifling used in .303 British barrels. The heavier barrel was free-floating, which meant that the required accuracy standard could be achieved without the barrel bearing against the wooden fore-end, as had been the case with the No.4 MkI(T). Therefore the woodwork was modified by shortening the fore-end to 1/2" in front of the middle band, and a new design upper handguard was fitted. The No. 32 3.5 power telescopic sight was refurbished and the bullet drop compensation on the elevation drum modified for the ballistic characteristics of the 7.62×51mm NATO cartridge in 50 m (55 yd) increments out to 1,000 m (1,094 yd). The modified version was renamed the "Telescope, Straight Sighting, L1A1". A new magazine suitable for the 7.62×51mm NATO cartridge was attached; it is recognizable by its more angular shape when compared against the .303 British version. A hardened projection of the left magazine lip serves as an ejector, although the .303 ejector screw remained in place. The butt with its screwed-on cheekpiece was retained, however the scope number on the wrist of the stock, was obliterated with "X"-outs, and new numbers applied. The markings on the left side of the receiver were obliterated and new markings reflecting the new rifle's designation and chambering were applied. The original markings are sometimes partially visible underneath. A new, larger transit case was made for the L42A1.