I have a brand new, never fired full factory N4 Infidel upper. I just F1 SBR’d the lower and swapped a Noveske 10.5” factory 300BLK upper on it, leaving the original upper in the Noveske Plano case.
It’s a 13.7” barrel with pinned Flaming Pig factory muzzle device. Factory CH, BCG, 15” MLok factory handrail, and factory Magpul Pro BUIS.
Hadn’t considered parting with it until I saw your post, so I’m not sure what it’s worth.