This is the cut code to restore you pre-1986 M16/M4 spec lower to have the special little hole needed above your safety selector.

Requires 1/8" drill bit and collet. Code for GG3 and GG3S Machines. Requires use of M16/M4 pocket lowers. If pocket is not milled to M16/M4 specs then you can use GGDs lower code to mill to correct spec. This cut code probes off of grip fin using 1/4" endmill then prompts to switch to 1/8" drill bit. Uses standard GG/DD plastic/3D Printed AR jig. Will slightly drill into jig but does not affect future jig function. Tested on forged AR15 lower. Have not attempted on billet lowers or using any other jigs (GGD Unicorn, 2APP, etc) or on AR10/LR308 or Pistol Caliber lowers (New Frontier C9, C45, etc). If tested on any of these others please send feedback to email included in file.