The drag line is the ring of surface damage caused by the cylinder stop pin on most revolvers. It is caused by the pin dragging over the surface of the cylinder as it rotates between shots. The damage is mainly aesthetic, and can spoil a high polish or blue finish on a revolver in a matter of days.

The drag line may be countered by applying a tab of electrical tape over the areas on the cylinder that would otherwise be affected. However, if the grooves are obstructed by tape the firearm may no longer function safely.

Emilio Gisoni's Mateba 6-Unica features an internal stop pin which maintains the cyliner's external blue finish.