The Action of a bolt action rifle is the heart of any rifle. Concentricity starts with every cut on the action being true and concentric to the rifles bore and chamber. We first start with mounting the action in the lathe. By running the mandrel in the bolt raceway absolutely true to the axis of the spindle. After the action is running true the truing process starts. All the cuts that are made to your action are made with it running true to the bolt raceway.