The M1917 Enfield, the "American Enfield" (frequently misidentified or mislabeled as the "P17", "P1917", or "Pattern 1917"), formally named "United States Rifle, cal .30, Model of 1917" was an American

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 modification and production of the British .303 caliber

.303 British

.303 British, or 7.7x56mmR, is a .311 inch calibre rifle and machine gun cartridge first developed in Britain as a blackpowder round put into service in December 1888 for the Lee-Metford rifle, later adapted to use smokeless powders...

 P14

Pattern 14 Rifle

The Rifle, .303 Pattern 1914 was a British service rifle of the First World War period. A bolt action weapon with an integral 5-round magazine, it was principally contract manufactured by companies in the United States. It served as a sniper rifle and as second line and reserve issue until being...

 rifle

Rifle

A rifle is a firearm designed to be fired from the shoulder, with a barrel that has a helical groove or pattern of grooves cut into the barrel walls. The raised areas of the rifling are called "lands," which make contact with the projectile , imparting spin around an axis corresponding to the...

 developed and manufactured during the period 1917-1918.
Before World War I

World War I

World War I , which was predominantly called the World War or the Great War from its occurrence until 1939, and the First World War or World War I thereafter, was a major war centred in Europe that began on 28 July 1914 and lasted until 11 November 1918...

 developed, the British had as its main rifle, the Short Magazine Lee Enfield (SMLE).