Setting the Sterling Mark 4 L2A3 Foresight on the Housing Tube
Use a piece of paper and a pencil to trace the top of the Foresight housing. Make sure to also trace out the hole on the insert. This will be used to determine the orientation and to center it on the tube:
Cut the rectangle out with a Razor. Center the circle of the foresight to the center of the barrel housing hole. Tape the paper to the Housing once centered...
Drill holes to remove the rectangle shape. This is REALLY IMPORTANT....DRILL ON THE INSIDE OF THE LINES OF THE RECTANGLE. If you drill on the lines, or outside the lines, your hole will be too big!
Once you are done drilling as many holes as you can, use a sharp razor to cut out the rectangle. Take your time with this step. You only get one chance to do this right and if you cut off too much, you will have patch work to do!