I have the same effects on my 340 cylinder- got careless and shot a bunch of old 110 gr SuperVel through it one day, found the cylinder looking just like the pictures. Not a huge deal- it has run flawlessly ever since. If I am paying attention, I only shoot 158gr loads, but I have so much old ammo that is out of the original boxes that sometimes a light bullet gets fired.
The pistol still does what I hired it to do- carry light and shoot hard.
Love it!