The SOCOM barrel is an approved SOPMOD barrel, mostly seen in the US Military SOPMOD M4A1 carbine. The front sight post variety became the M4A1 Block 1 featuring the Knights Armament RAS quad rail, while there were also Block 2 rifles using the Daniel Defense RIS-II FSP rail, with the front sight post sticking out of the rail. Other Block 2 rifles with the flat top Daniel Defense RIS-II M4A1 rail used either a SOCOM barrel or an M4 Government profile barrel, both with the front sight posts removed and a Mk12 gas block from NAVSEA installed.
Colt and FN provided the bulk of the 14-1/2" SOCOM M4A1 barrels, but so did MMC, another government contractor. This barrel is a surplus barrel, new old stock from MMC. New old stock means that the barrel is new - never installed - but is old stock, probably sitting in a warehouse for a number of years. The barrel has been stored in oil and milspec plastic packaging and is in perfect shape, even including the cardboard wick. All government contract barrels were built to the same military specification.
