The L64 (also called the Enfield Individual Weapon) was an intermediate calibre British bullpup layout prototype assault rifle developed in the 1970s. At one time it was known as the 4.85 Individual Weapon, a reference to the calibre of the bullet it fired.
The British Army had considered bullpup designs with intermediate calibre rounds in the 1950s, and officially adopted one of these as .280 British in 1951 in the EM-2 and Taden gun. However, US intransigence during NATO standardization efforts, and Winston Churchill's interest in standards above all, led to the adoption of the 7.62×51mm NATO round. This was significantly more powerful than the .280, and could not be easily adapted to the existing weapons. Instead, the British and Canadian armies adopted the L1A1 SLR, a licensed version of the FN FAL, itself originally designed for the .280.
During the 1960s the US found that, as the British had suggested, the 7.62 NATO round was far too powerful to be used in a fully automatic rifle. After considerable wrangling, the US Army eventually adopted the M16 rifle, firing the .223 Remington cartridge of much lower power than even the .280. With standardization "broken", the British Army once again started researching lighter rounds in the 1970s. These efforts suggested that a round of similar weight as the M16s, but firing a smaller diameter bullet, would offer the same recoil patterns while having much better penetration and ballistics. The result was the .190-inch (4.85 mm) round fitted in "necked down" but otherwise standard 5.56 mm cartridges from the M16.
L64 may refer to: