If you are talking about the curved mark ending at the center pin hole:

Yes, that is normal.

It is extremely unlikely it is .010" deep, maybe .002-.003".

Of course you should lubricate that area, just like the rest of the gun!

This has nothing to do with rounds fired, and everything to do with how many times you have opened and closed the cylinder, whether loading & un-loading or just playing with it.

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Gunsmithing since 1961