FN M16A4 Upper Receiver

[3ACR_Scout]

Hi folks, this may be a long shot, but I’m trying to track down an FN (FNMI) M16A4 upper receiver - an actual rifle upper without M4 feedramps. I’d like to find one with the Cerro keyhole and “F” forge marks, but I’m open to other versions. I don’t need a barrel, just the upper receiver itself. I’d appreciate any help you could offer. Thanks!