...Any infantry rifle is supposed to be good in an infantrymans hands out to 300mtrs individual firing, out to about 600mtrs as a section shoot, then it is a snipers job using optics....
National Match competition (High Power) is held with 300 yards classified as "short" range, 600 yards as "medium" range, and 1000 yards as "long" range. All fired with an M14 (or occasionaly an M1 Garand) with open sights.
The Marine Corps also still uses this range classification system; although they don't expect long range coverage with an M16 or M4.