Eric: I recently installed one on a first generation Colt M4. First, to remove the rivet on the bottom swivel-Use the size bit that just contacts the "foldover" on the rivet. There is no standard size, as I have seen many different styles of rivets used. Put light pressure on the bit, and keep your drill at a low RPM. It is not a hardened steel, so it wont take too many revolutions to cut into the rivet. When you start penetrating the "foldover" use a small punch and LIGHTLY tap the center of the rivet. It will break the foldover and push the rivet through. The side sling adapter uses two roll pins pressured against the spring steel. Its a little tricky to get started, but be patient and it will go. Good luck.