Do you have an Apex flat trigger installed in your CORE and need an over travel set screw? The standard CORE OT screw is too short and a longer one is too narrow. I used a 6-40 x 5/8 Hex Drive Flat Head Screw to solve that problem. You need to cut a slot in the small end so you can adjust with a small screw driver. The head measures about .270 so I filed it down to .220, using a dremel and file. I also had to trim the back of the trigger blade so the screw head would hit the trigger instead of the blade. You also need to remove the trigger to install the screw. YMMV

Enjoy

Philip