I don’t think you have that piece installed right


Ignore the integrated anti rotational tabs in this photo
Name:  9AD102E9-F402-4F20-B352-602F6B82A9DB.jpeg
Views: 546
Size:  64.3 KB

You’ve got this piece turned (so it appears from your photo) that it’s acting like an anti rotational tab rather than flush like so
Name:  38F6A11E-276E-4345-BBC0-50BFA72E99F6.jpeg
Views: 540
Size:  403.2 KB


I get my rails flush with the upper receiver by mounting an A4 carry handle across the gap and helping to align them while I tighten the rail hardware up