This new SOST round from ATK/Federal Cartridge and was engineered for the USMC as a supplemental/replacement round to M855 green tip with more desirable terminal characteristics. Designated as MK318 MOD-0 the round was designed as a barrier defeating round with superior penetration and better ballistic stability when shooting through glass, car doors and other barriers where other rounds simply bounce off. It was engineered after the Marine Corp identified issues with the M855 round. MK318 utilizes a 62 grain open tip boattail match bullet with a lead core and reverse copper jacket creating the open tip. We shot some this past weekend and from our match 16″ barrel we got under 1 MOA off a bench @100 yards. Supplied from the factory in 500 round cases with white boxes Part# T556TNB1.  Be wary of some of the stuff you see on the web.  There is already some reject surplus stuff popping up in ammo cans at cheap prices.  You get what you pay for and ammo is the last place you want to buy junk.  We found it here… TM