All New Model Ruger SAs are subject to a cylinder drag line .... the more you use it, the deeper the drag line. Why? All New Models to include Single-Sixes, Blackhawks, Super Blackhawks, Vaqueros and New Vaqueros share the same cylinder latch and hammer design. Here's what happens: At rest, the cylinder is latched and won't rotate. When you start cocking the hammer the hammer plunger contacts the cylinder latch and pulls it down, releasing it so the cylinder can rotate. The pawl starts to rotate the cylinder and just about 10 degrees into rotation, the hammer plunger cams off the cylinder latch. This allows the latch to pop up under spring tension and contact the cylinder. As the hammer and pawl continue to rotate the cylinder, the cylinder latch will rub on the surface between lock notches and create a drag line.
I designed a fix for this condition but with blued guns, you need to do the modification before a drag line is created. Stainless guns are more forgiving because you can use a 3-M pad to buff out the drag line and make it look factory fresh.
The modification involves a making longer hammer plunger out of a 3/32" drill bit shank. This holds the cylinder latch longer into the rotation cycle so he cylinder latch will release just as it starts into the leade of the cylinder's lock notch.
Here's a hammer with a factory plunger on the left and hammer with a modified extended plunger on the right and a graphic of the plunger with the measurements:
