I torque mine to 45 inch pounds for starters. You want to keep the pressure at a minimum to prevent damaging wood. If you can tell it is too little: stock wiggles, group stringing etc, go up in 10 inch pound increments.
If that doesn't change anything and everything seems to be tight and functioning correctly, you probably have the wrong powder charge (usually not enough). This is one of the most common causes of vertical stringing.
Good luck,
Chris