When will the M16/M4 be replaced? It's been a popular question looming over the last 50 years or so. It has been attempted numerous times throughout the years through the ACR trials, Individual Carbine, as well as many others. For some reason, in the end, we stay with what we know works. Looking back to World War II, we saw a transformation from semi-automatic combat rifles, and in the post war era we saw the introduction of the intermediate caliber. Towards the end of World War II, we saw iron and wood turn into stamped sheet metal (StG44).
Now along comes the 1950's which really was the dawn of the aircraft age; the introduction and usage of modern aluminum and polymer components. Eugene Stoner from ArmaLite introduced a groundbreaking application of the modern materials to the firearms industry. Like any change, the industry went kicking and screaming into a new age. Another major change was the introduction of the barrel extension which decreased the weight of firearms. This would be a major change in the firearms design and be adopted in designs all over the world. Direct gas was viewed as an improvement over external piston by the testers of the AR10 and AR15 at Aberdeen, although the head poobah told the testers to erase the comments.
The AK47 also remained nearly the same with minor production improvement and caliber changes. It was a solid design and it worked. Soviet doctrine was fulfilled by this rifle. Precision accuracy was not important, but short range full auto firepower was. Since World War II the major Soviet tactic was massive bombing and artillery bombardment, and then, mobilizing overwhelming infantry at close range.
The US was quite different in their requirements. And the AK-type rifle would not meet the requirements at all. Longer range precision accuracy was a requirement, as well as, many human engineering factors (easy to use, controllable, modular, etc…..). The AK really only has evolved with the change in caliber to 5.45x39mm but core design has stayed the same. Brutally reliable, poor human engineering, poor accuracy beyond 150 yards compared to its American counterpart, but it fit the need of the Soviet conscript Army.
In the mid 1980's, NATO standardized on the Belgian SS109 cartridge as the new 5.56x45mm NATO round. The M16 was readily adapted to this new caliber and its unique needs over the Vietnam-era M193. New barrel twist plus numerous improvements over the M16A1 including stronger furniture, shell deflector, reinforced receivers, sights fully adjustable for use with the longer range potential of the M855 round. In the mid 1990's the M16A2 would morph into the M4 carbine. Again adapting to new conditions of mounted warfare, lighter for carrying and many accessories introduced such as rail systems, optics, lasers, IR scopes, night vision, as well as, vertical pistol grips. Following suit came the M16A4 which gave the adaptability and modularity of the 14.5 inch M4 carbine to the 20 inch full size rifle. The AK remained the same. For military use you had difficulty adapting any of these components to it. Some rifles would be issued with a side mounted scope, but general issue still did not make use of scopes and optics of other sorts.
The early years of the Global War on Terrorism sparks the newest debate: Is direct gas impingement inferior to the old technology of the external piston? This was brought out by issues SOCOM has had with their M4A1 carbines. Originally they had claimed the rifles were deficient and "fundamentally flawed". Reality was they were using a lightweight carbine in the role of a light machinegun. The weapon evolved once again into the SOPMOD M4A1 carbine. The barrel was made into a heavy barrel to better deal with the SOF higher rate of fire schedules. Around that same time the SCAR or Special Operations Command Automatic Rifle program was initiated.
This was for a new firearm designed specifically for their needs and they would become the project manager of. The final two were the Colt Type C and the FN Scar 16. Based on soldier feedback, they felt there was more of a future in the FN entry and it was adopted. In the meantime, the new M4A1 rifles came out and were used by SOF with little issues. The SCAR 16 was plagued with issues, enough so that after a few years of trying to get the gun ready to put in service, they cancelled the program in favor of the new SOPMOD M4A1 rifles. The MK26 offered no performance enhancement over the M4A1.
Heckler & Koch would launch a very aggressive marketing campaign claiming their HK 416 was superior. The rifle got very mixed reviews. It got feathers riled enough that Senator Coburn demanded the Army do a full open competition test to see if our military had the best rifle. The Army stated that they were pleased with the rifle and saw no need to replace it but they were forced to run the competition. Many companies submitted. It was down to four different rifles. All rifles were tested with the new M855A1 ammunition, which was higher pressure. None of these companies were provided this ammunition to design their firearms around.
All 4 failed the durability testing with the new ammo. The competition was cancelled. The M4 would remain. However, this did lead to an M4 upgrade program. This would replace the barrel with the new SOCOM heavy barrel; replace the burst fire control with an auto; and, make the rifle ambidextrous with an ambi safety and magazine release. This too was cancelled after a brief time. As of 2017, all rifles procured are in the SOCOM M4A1 configuration.
This leads us back to the question, how long until this family of weapon are retired for something new? My answer is I think we have reached an evolutionary peak in the industry. All military rifles are very similar in mechanism and modularity. We see newer lighter materials, some changes in finish and coatings to the barrels but mechanically about the same. Nothing coming out really offers enough of an improvement to move forward.
I believe we have reached the peak with the use of the metallic cartridge. Until we see some new form of ammunition (caseless, for example, or a laser gun!) I do not see any change. With the new technology for ammunition, we will see the next evolution in small arms. The M4/M16 has changed with new battlefield requirements successfully since 1965. Through changes in materials, changes in battlefield environment, as well as, all the new optic technology. The ability to change out with different cartridges has yet to be realized within the military (300 Blackout, 6.8mmSPC for instance).
The platform still has much life in it. I believe it will continue to serve until we reach that new thing. I believe the same for the AK47 on the Russian side. We have seen the evolution to the AK74. We have even seen the AN94 officially replace it, yet never go into production for anyone out of SPETZNAZ. It was too expensive and complicated to produce so we have the AK74M. New rifles are showing some presence but the core is still the AK-series. Like everything in life, it is up to speculation and debate, but this is my opinion.