A good rule of thumb for LOP is to place the butt inside your elbow and see if you can comfortably reach the trigger. You can remove the stock, hold the action with your finger on the trigger, place a yard stick inside your elbow running inside the action. Read the rule where it reaches the end of the action. That is not LOP but the length your stock should be. Add that to the length from the rear of the action to the trigger should give you LOP.