Hi Everyone: The ejected casings of my .380 PPK/S have some powder residue or carbon burn marks that covers almost half the circumference of the case and run 3/4 of the length. I'm using the Winchester "Win-Clean" ammo. Is this normal or do I have a worn chamber or out of round chamber problem. The pistol is of 1991 vintage made by Interarms and functions perfectly in all other respects. Any input is appreciated. C.Good.