Length of the Back Swing

The important thing about the backswing is the torque you generate in the upper body. You need to feel tightness in the torso while keeping you lower body relatively stable. If your shoulders rotate 90 degrees, your hips rotate 45 degrees, your knees 22.5 degrees and your feet are the base. When you uncoil, you turn your lower body first, which uncoils your upper body which gives speed and lag to your swing. The thought you need to have when uncoiling your lower body is to have your right knee touch your left knee. the arms will follow the rotation. This is something you can repeat consistently and therefore have similar results shot after shot. Here is a video that explains the mechanics and showcases how the coiling and uncoiling of the body work.