Nothing generates passion like discussing the Army’s primary weapon, the M4/M16 family of 5.56mm carbines and rifles. Virtually every gun related blog has long, long threads with suggestions for better weapons and demands for a different caliber.
But the Army has polled its troops repeatedly, and to some surprise, the troops are generally very happy with the M4. The have a great deal of confidence in the weapon, and they like it.
And let’s face it, absent some miraculous change in small arms technology, any change to a new weapons would be an incremental improvement at best.
But that doesn’t mean there isn’t room for modest improvement in the M4. The M4 carbine, a shortened, lightened version of the long-serving M16, was originally fielded two decades ago. It was never actually intended to be the primary weapon of the Infantry.* Instead, it was intended to equip soldiers that needed something more than a pistol, but for whom the length of an M16 would be awkward. Tankers, other armored vehicle crewmen and such.
But the handy little carbine was soon adopted by airborne and air assault infantry, for whom the weight savings were important. And the small size of the carbine made it popular with mechanized infantry as well, for the close confines of the troop compartment of their vehicles. And in Iraq, with close quarters combat inside the maze of buildings soldiers faced every day, the compact carbine was far easier to use than a full sized rifle. Eventually, the M4 ended up as the primary weapon for just about all ground combat troops.
One of the biggest complaints from the field was that the M4 used the same trigger group as the M16A2. It could fire semiautomatic, or it could fire a three round burst. But the burst feature was unpopular. Initially designed to save ammunition, it has some mechanical features that are annoying. If, when firing a first burst, you only hold the trigger long enough to fire one or two rounds, the next burst will not be a three round burst, but rather the two or one rounds not fired before. And the trigger pull required increases. Finally, while most of the time, suppressive fire should be in nice controlled bursts, there are times when longer bursts are needed.
And so, back in 2010 The Maneuver Center of Excellence (formerly the Infantry Center and School) requested that the Army switch to a fully automatic version of the M4.
As it turns out, there is, and has for 20 years, been a fully automatic version of the M4. When the M4 was first designed, Special Forces and other special operations entities liked the carbine very much, but insisted on a fully automatic version right from the start.
The M4A1, the fully automatic version, has a different trigger group, similar to the old M16A1 rifle that allows semiautomatic or fully automatic fire. Because of its potentially higher rate of fire, the M4A1 also has a somewhat heavier barrel, to better withstand the heat of firing.
While the Army is buying some newly built M4A1s, the majority of M4 carbines in Brigade Combat Teams will be modified to the M4A1 standard. Contact teams with conversion kits are travelling from the Army’s main small arms depot at Anniston, AL to various posts and modifying weapons one BCT at a time. Within a couple years, the process should be complete.
*Most Marine riflemen still carry long M16s.