I added a slot for a M5 square nut in the grip so the screw is metal on metal and to avoid needing a tap set to install the grip. This is a similar design to how the UMP 11/9 grip is installed without a tap set.
LBRY Tags: balr; nopel; remix; 3d2a; lowerreceiver
AR15 Lower Receiver Reference (Anotated F3D, STEP, STL)