I've learned a great deal about this subject recently during and since my attendance at a Project Appleseed event in January from several sources but much of it from this wonderful reference on the beginnings of the American Revolution. The American or "Kentucky" Long Rifle, with its rifled barrel had been in use since the early 1700s, long before the American Revolution, mostly in Pennsylvania and Virginia for hunting and had an effective range of over 200 yards in the hands of a skilled marksman. They had also been used in combat during the French and Indian War (1754-1763). The disadvantage of the Long Rifle in 18th century combat was that it took much longer to reload than the British Brown Bess muskets in use by most of the British Regulars, whom were lucky to be effective to as much as 100 yards but usually only out to about 60-70 yards. A well trained 18th century soldier could fire three rounds a minute from a smooth-bore musket while a rifleman required much longer to force the tight fitting ball required to take advantage of the rifling in a muzzle-loading rifle. However, the rate of fire advantage for smooth-bore muskets would be countered by Riflemen using different tactics then considered dishonorable by the British.
The Continental Congress created the Continental Army in June of 1775 after the Battles of Lexington and Concord on April 19, 1775. They called for the formation of 10 Rifle Companies from the middle colonies and decided to send two of them to Boston. In response, Virginia chose Militia Colonel Daniel Morgan to lead one of them. Colonel Morgan used a shingle as a target set at 250 yards to recruit the best marksman to form his rifle company. In 10 days he'd recruited 96 riflemen and on 14 July, 1775 he marched them 600 miles in 21 days from Winchester, Virginia to Boston, Massachusetts. His Rifle Company used guerrilla tactics and targeted the British Officers and the Indian guides used by British when traveling over rough terrain, creating chaos among the British since they often decimated the leadership of British units they encountered.