Originally Posted by Tench
I always thought the hammer rail was stainless steel? The rust has probably come from the inside of the hammer? A dry lube is certainly best as oil will create inconsistency, oiled and wiped off as Andy says is probably best.
This. The rail is stainless and the corrosion comes from the inside of the striker, falls onto the rail and mixes with the factory grease which then dries and forms the brown caked-on crap you describe.
FWIW I polish the rail, clean the bearings out with some blue roll and oil, take any corrosion off the striker with 0000 wire wool and oil then lightly coat the striker with oil to prevent further corrosion.
You're certainly fine running the striker dry, or as Simon suggests a dry lube if you must put something on it!