The M4 rifle platform is a timeless and history-defining weapons system, tried and tested through years of conflict… but it wasn’t perfect. Near the turn of the century and the more modern theaters of war, it ushered in, the US Army started getting complaints that the rifle didn’t perform very well in close-quarters situations due to its 20-inch barrel, which was good for higher muzzle velocity and increasing effective range, but not great for door kicking. So the NSWC Crane division got to work developing a new platform, one more suited to CQB scenarios. They came up with the CQBR (Close Quarters Battle Receiver), re-designated as the MK18  Mod 0 and Mod 1. Sporting nearly half the barrel length of the M4 yet still having impressive ballistic performance, the MK18 was here to stay