it is common for AXG frame threads to not be fully tapped or clogged with anodizing debris.We recommend clearing the threads by slowly working the screw with a drop of oil & turning it Clockwise 1/4 turn, then Counter Clockwise 1/4 turn, until the threads are clear.If you do meet heavy resistance a tap is the best way to clean the frame threads. As the hole/threads are at an angle & the mag well sits flush, the screw will not sit flush with the frame but keeps tension on the back edge of the KATANA hole.