How much fire power does M4A1 have?

Answer 1

the m4 fires a 556 mm NATO round which is only about the size of a 22 calibre round. The reason its effective at all is because of the amount of grain in the casing, giving it a high muzzle velocity

Clarification to the above answer:

Hitting/stopping power (terminal effects) is different than firepower. Firepower, by definition is the AMOUNT of rounds you can put downrange effectively. The M16/M4 family has a cyclic rate of about 600-800 rounds a minute. With a standard 30 round magazine (and the capability to accept much higher capacity mags), the M4 has about as much firepower as any assault rifle out there.

Terminal effects is a much murkier thing and harder to quantify. While it doesn't hit with the same energy as, say, a 7.62mm NATO round, it tends to do more tissue damage due to the fact that it's lighter bullets will fragment causing huge wounds out of proportion to bullet size. Mpre tissue damage = more bleeding = increased lethality. The issue with the M4 is that, because of it's shorter barrel, it has decreased lethal range when compared to an M16 (slower bullets tend not to fragement as readily, and the M4 has 20% less muzzle velocity than an M16). The M4 was never intended to replace the M16 because of this shortcoming.