Several highly rated brands of .22LR ammunition for the Colt M4 are Norma USA, Fiocchi and American Eagle. Each brand specializes in a particular type of ammunition.
Customers at Cabelas.com rate Norma USA Match above all others citing its consistent accuracy. These cartridges are 40-grain, lead round nose bullet with a muzzle velocity at 1,100 f.p.s. For a high-velocity round, users of SportsmansGuide.com give Fiocchi’s 40-grain, copper-plated special purpose round high marks. The muzzle velocity is 1,255 f.p.s. For general plinking, the users recommend American Eagle 38-grain, copper-plated, hollow-points with a muzzle velocity of 1,280 f.p.s. It is considered a good value that doesn’t sacrifice on quality.