Another thought:

Are you sure that the maks inside the barrel are pitting and not lead fouling? People who shoot .38's often shoot lead bullets through them. The stuff can be pretty tough to get out at times and makes the inside of the barrel look blemished. Try taking some COPPER wool- like the stuf used for cleaning kitchen pots and pans, cutting patches of it and scrubbing the bore out. If its lead, this will remove it.