Evolution of the M4 Carbine

Steve Johnson
by Steve Johnson

PEO Soldier, the Army acquisition agency, have published a timeline showing the 62 ECP (Engineering Change Proposals) that have been applied to the M4 Carbine over the past 18 years. The original specifications called for 600 Mean Rounds Between Stoppage. The current reliability of the Carbine is over 3600 MRBS. COL Douglas Tamilio writes [PDF Link] …

The Army is committed to continuous improvement in all of our weapon systems. For example, the reliability requirement for the M4 is 600 Mean Rounds Between Stoppage (MRBS). The demonstrated current reliability is over 3600 MRBS as a result of our continuous improvement program. To date there have been 62 improvements to the M4, which include improvements to the trigger assembly, extractor spring, recoil buffer, barrel chamber, magazine and bolt. The M249 SAW, the Army’s Squad Automatic Weapon, has a reliability requirement of 1200 MRBS and yet today demonstrates a reliability of over 23,400 MRBS.

M4 Evolution Timeline. Click to here to expand.

Yesterday I wrote about the next set of changes to the M4 that the Army proposes to make, which include adding ambi control, a piston and heavy profile barrel. Clearly the Army does not believe the M4 has reached the end of its useful lifespan.

It appears that the M4 replacement testing is over before it began and that any testing that does take place will be to pacify the congressmen and women who are calling for the M4 to be replaced.

  1. The M4 entered service in 1997, but development of the XM4 carbine started at least as early as the mid-80s. 

Steve Johnson
Steve Johnson

I founded TFB in 2007 and over 10 years worked tirelessly, with the help of my team, to build it up into the largest gun blog online. I retired as Editor in Chief in 2017. During my decade at TFB I was fortunate to work with the most amazing talented writers and genuinely good people!

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  • Zach Zach on Mar 05, 2010

    I have to agree with Lance, weaponology (lol) and shows like that always say that there are reliability issues and that its too small of a round, like that one dumb "Top 10 Battle Rifle's" that ranked the M14 10th and the AK-47 1st. I think the M16 platform came in 7th or something. But if the soldiers like it, then it's obviously a good weapon. Although I believe the HK416 is a fantastic weapon, super reliable, accurate, and the controls are identical to the M4

  • HK_USP_45 HK_USP_45 on Mar 05, 2010

    Zach, I agree. And I think most criticisms of the M4/M16 from the guys in the field are about the caliber, not the rifle itself. The AR rifle platform is outstanding.

    lance, aren't a lot of M4 uppers made by FN for Colt to supply for the gov? I would hardly call FN junk. The Scar might need some work, but as I said, I wouldn't say FN makes shoddy products. I think with the Scar, FN was trying to get it fielded quickly, and it's got some stuff to work, but it will get there. No matter how much you beat up and test a combat weapon, you can't simulate the battlefield. Stuff that didn't break in reliability testing, will break in the hands of a soldier or Marine. Let's face it, we find new and better ways at breaking things, and we're good at it. I for one can tell you that with the level of creativity a Marine can come up with to break things, I think it's an artform. But if the military uses the Scar, it will evolve into an outstanding product, just like everything else FN offers. That's what good companies do, they take feedback from the field to make design improvements.

    Very few battle weapons have been perfect right out of the gate. I mean, look how long it took to get the M16 right, and look at what it's become now. You can say that about just about every weapon we've fielded. That's why everything has an "A" followed by a number after the nomenclature.