This evening I again tried another NIW FDE Pmag (12/08 Manufacture) and it also did drop free. This mag has never been loaded either. I then unloaded one of my older black Pmags (11/07 Manufacture) and tried it in the rifle. It did not drop free when empty. I thought that the second mag didn't drop free because it had been stored fully loaded for at least six months.I then found a NIW black Pmag with a 11/07 manufacture date and it wouldn't drop free either. Now it appears as though there must a slight different between the mags with a 11/07 and 12/08 manufacture date. What this difference is, other than fit, I cannot attest to. Just a little FYI.