Special Operations.Com

Despite the popularity of the older CAR-15 and it's immediate successor, the Commando-both models lacked one important thing.  That being the ability to hit at longer ranges, both models were more effective as sub-machineguns that as true carbines or even rifles. So in 1988 engineers at Colt began working on a new carbine which they felt would be a viable alternative to previous designs.  The M-4 was to take advantage of the lessons learned from previous attempts, for one the weapons foregrip was engineered with a double heat shield.  This would keep the users hand from being scorched by a a thin heat shield coming from a hot barrel (see Figures 2-1 &  2-3).  An earlier design flaw noted in the CAR-15 was avoided when a heavier barrel was used-this would allow the weapon to be used "aggressively" with a bayonet (see Figure 2-4).  In many respects the early designs were quite similar to the M-16A2 already in production, in fact 80% of the parts used in the manufacturing of the M-4 are compatible with the M-16A2 (Note The A2 Receiver On Figure 2-2). The early models of the design (Model 720) were often referred to as the M-16A2 Carbine as a result of the resemblance between the two weapons.  Strangely enough there is a different version of the M-4, known as the Model 723-instead of using a M-16A2 receiver it is mounted with the receiver and rear sight from the older M-16A1 (see Figure 3-2).

One problem with the earlier designs which Colt improved up was using a slightly longer 14.50 inch barrel, the result of this was to give the weapon more range and also to allow it to use the M-203 grenade launcher.  The addition of the latter would be greatly appreciated by units who were issued the weapon.  Now they had in effect a weapon which was more compact than the M-16A2, just as accurate and capable of hitting out to longer ranges and capable of giving them a tactical edge with the M-203 and later PI-M203.  In 1994 the United States officially announced that the M-4 Carbine Series would replace the venerable M-3 Grease Gun in use, as well as selected M9 semiautomatic pistols, and selected M-16A2 rifles.  The typical Colt M-4 Carbine is fitted with a three round burst limiter, Colt however has produced a M-4A1 model which is identical in most respects to the M-4 except it is capable of firing full automatic.