Evolution of the M4 Carbine

    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 years1. 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

    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!