So i bought an upper and didn't inspect it enough before I closed the deal. Well, it turns out I have an upper with the M4 ramps cut out but have a barrel without M4 feed ramps. After I built my lower I cycled some rounds through it and that's how I found the issue. Neither have been fired but have marks associated with cycling a few rounds for function test. I'm looking to trade either the upper receiver (flat top) for the same without M4 feed ramps or the barrel for one with M4 feed ramps. The barrel is a stag 16" carbine barrel 1/9 twist. I don't know who made the receiver, No T marks. If you have a 1/8 or 1/7 twist I'm good with that! If you want pics I can send them via text or take some better ones and send them through email.