It seems to me that this would tend to deform the leading edges of the lead bullet. I'd appreciate your insight. As the full wadcutter is commonly loaded in .38 Spl. Occasionally, none of the factory provided seating plugs will seat a certain bullet without deforming the lead. You didn't specify if you are loading cast or swaged wadcutters.
Cast bullets are generally of a much harder alloy than their swaged, or cold extruded, counterparts.
A seating plug that is a close but not perfect fit can be used on the harder cast bullets without experiencing any deformation.