I don't have a Kreighoff insert, but my insert is similar. The tiny screws are windage and elevation adjustments. The key is to to keep the insert in the same position each time the insert is placed in the barrel. My drilling has a notch filed in the extractor and a matching pin on the insert. Place the insert's pin on the notch and tighten the insert. Then fire, loosen, adjust point of impact, tighten, shoot again and repeat as necessary. Good luck!