The basic weapon system, in its highly compact M4 variant, remains in service with the U.S. military today, with a superb ...

Despite early controversies and setbacks in Vietnam, the M16 proved its worth. The rifle's design has evolved, leading to variants like the M4 and specialized models used by special operations forces.

One of the main differences, though, is that it has a longer barrel length. The M203 shoots 40mm grenades and can be fitted under the M4 and M16, but the Army is currently phasing it out for the M320.