January 14, 2008: The U.S. Army has largely adopted the M4 Carbine as its standard infantry weapon. This weapon has been around since the early 1990s, when it was adopted for use by SOCOM (Special Operations Command). This was a special version of the M4. SOCOM often takes the lead in developing new weapons, or versions of existing ones (like the M4, a modified M16 design). Once SOCOM has demonstrated that a new item works in combat, the army and marines are inclined to consider adopting it as well. The M4 is much more compact than the M16, not just because of the shorter barrel, but because of the telescoping stock. This makes the M4 much easier to use by people in vehicles, or for combat support people who must carry around, but rarely use, a rifle.

The M4 is 33 inches long and weighs 6.9 pounds (with a 30 round magazine.) In contrast, the M16 weighs 8.5 pounds and is 39.5 inches long. The M4 has a 14.5 inch barrel, while the M16's is 20 inches. The other main difference between the two weapons is that the M16 is more effective at longer ranges (over 300 meters), because of its longer barrel. But combat experience in the 20th century demonstrated time and again that most (over 90 percent) of the time, your average infantry soldier did not need a personal weapon that was optimized for long range shooting. Almost all combat took place at shorter ranges. It was more effective to have specialized weapons (light machine-guns and larger caliber sniper rifles) for the long range stuff, and a lighter and handier weapon for close in work.

For years, there have been controversies over the wounding power of the 5.56mm bullet used in both the M4 and M16, as well as the reliability of the firing mechanism for both rifles (which have 80 percent compatibility of components). The army has surveyed the troops several times, and conducted many tests, to try and settle these disputes. The basic finding is that 89 percent of the troops had confidence in the M4, but did have complaints about jamming and the hitting power of the 5.56mm round. Changing to a new weapon would cost several billion dollars, and none of the proposed candidates, as far as the generals were concerned, had a dramatic advantage over the M4 (and could end up introducing new problems.) So, for the moment, the M4, a smaller version of the 1950s M16 design, remains. The U.S. Marine Corps is sticking with the M16 for most of its troops, but has junior grade officers carrying the M4 instead of a pistol.