IIRC, when the unit that Jessica Lynch was a part of got ambushed in Iraq, the DOD after-action assessment was that personnel with active duty non-combat units and NG/AR units needed to increase their training with their M16s, and DOD increased its annual ammo needs by a multiple.
That caused a shock wave, since LC was already running flat out. A relative who monitors govt contract awards sent me a link to the notice that DOD had issued large ammo contracts to both Winchester Olin and IMI in order to supplement LC's production of 5.56. IIRC, when that news hit, there was even a flap about the IMI ammo causing a problem in the Muslim world, so the directive was that the IMI ammo would be used stateside, while the Federal and Win ammo would go overseas.
It was shortly after that when the IMI-made Q3131A began to dry up. When I visited a gun dealer near my range yesterday who is a diehard Win ammo dealer (I don't get there often, too far away to just "drop in"), I noticed that the only Win .223/5.56 he had was cases of the subject M855. It was also expensive, and since the dealer near my home still gets periodic quantities of XM193 for $115/500 and M855 doesn't do as well in my 1x9 as the M193 does, I decided to pass on the Win M855.
So it's no surprise to me that Win M855 has hit the civilian market. It's the same circumstances that made Federal XM193 and XM855 available to us .... contract run product that won't meet milspec requirements (usually improper primer and case neck sealant) and is packaged and sold to us civies to recover the cost.