Great grandfather to the .50 cal sniper rifle?

The Boys anti-tank rifle Mk I was made by the British in world war two. The round that is fired was 13.9x99mm, to give you an idea of how big that is the modern day .50 cal bullet is 12.7x99mm. This rifle fired a larger round than its modern day counterpart. The Mk-1 was in service from 1937 - 1943. It was used by almost every country in world war two. It weighed in at around 35 pounds and was 5 feet 2 inches long.