If you’re trying to order the carrier key screw, NSN 5305-00-992-7284, and it’s being cancelled, here’s why. There’s an error in the DLA system, and they’re working to fix it. Until then, order the next higher assembly. That’s the key and bolt carrier assembly, NSN 1005-01-441-1619.
Until this issue is resolved, you will be spending an additional $80 but in the end, you save an undetermined amount of NMC time.