There was also the utter decimation of the British officer corps at Saratoga by other riflemen, and even earlier.
The British learned to hate American rifles early:
‘The Loyalist Bradford brothers, Philadelphia printers, wrote the following story which appeared in the London Chronicle on August 17, 1775: “This province has raised 1,000 riflemen, the worst of whom will put a ball into a man’s head at a distance of 150 or 200 yards, therefore advise your officers who shall hereafter come out to America to settle their affairs in England before their departure”.’
‘These marksmen were organized into small, independent units and ordered to pick off British officers during the inactivity around Boston after the Bunker Hill fight. Dunlap’s Pennsylvania Packet said on August 14, 1775: “The express, who was sent by the Congress, is returned here from the Eastward, and says he left the Camp last Saturday; that the riflemen picked off ten men in one day, three of whom were Field-officers, that were reconnoitering ; one of them was killed at a distance of 250 yards, when only half his head was seen.” Such reports caused great indignation when republished in London. The backwoodsmen were called “. .. shirt-tail men, with their cursed twisted (rifled) guns, the most fatal widow- and-orphan-makers in the world”. ‘
From: http://www.revolutionarywararchives.org/longrifle.html
Funny thing was that most of these rifles were made in small town and rural outbuildings with less sophisticated equipment than today's average garage.