The M4 complaints are based on two factors. First is lethality. When the Army moved from the M16 to the M4 they reduced barrel length from 18 inches to 14.5 inches. The decrease in barrel length reduced projectile muzzle velocity, which when combined with a 62 grain steel core projectile, affectionately known as green tip, of the M855 round resulted in poorer terminal effects. Hence the lethality issue.
Second, the operating system used in the M4 carbine is a direct gas impingement system, which means that after the bullet escapes the barrel, a small amount of gas is allowed to return back to the receiver to unlock the bolt pushing back the bolt carrier group and cycling the action – ejecting the spent case, loading a fresh round in the chamber and locking the bolt for the next shot. The gas that is diverted back to the receiver is hot, under high pressure and contains minute particles of powder residue. Hence the alleged reliability problems.
To deal with the lethality question, the U.S. Army commissioned an enhanced version of M855 designated M855A1. The new round combined the use of improved propellants with bullet composition and geometry to improve terminal ballistics. Nothing in M855A1 should be cause to redesign a weapon. If it fires M855 reliably it fires M855A1 reliably.
Weapon reliability issues have two drivers.
First, the services do not have a systematic means of performing maintenance of the weapon system. You and I can look at the odometer on our vehicles and asses that we need an oil change or a tune-up. As an NCO in CA NG, when one of my guys had a weapon problem you took it to the armory. It is a reactive process as opposed to proactive. Fabrique National (FN) developed a shot counter that can be installed on the weapon. Like a gun odometer, it keeps track of shots fired thus making the maintenance process systematic and proactive. In my opinion, it should be used DoD wide, but regrettably it is not. Someone should ask why not?
Finally, soldiers don’t like spending down time cleaning weapons and magazines and that is a behavioral issue that needs to be handled at the squad level. All weapon systems operating in harsh combat conditions require so level of maintenance including the venerable AK-47.
The M4 family of weapons are effective, reliable, highly configurable and lethal, given field performance reports on the Enhanced M855 ammunition (M855A1).
In closing, although there are several advanced weapon systems available to the DoD that are truly exceptional (e.g. FN SCAR, Beretta ARX, HK416 and HK417, Steyr AUG which are a few of my personal favorites) the question has to be asked are they sufficiently exceptional to replace a 500,000 + unit inventory along with the supporting parts, training and logistics. Is there a business case? I haven’t seen that made, so any effort to replace the M4 seems whimsical. This is our 2¢ worth on the topic.
Source: Washington Times Article.