I am reloading blazer, Winchester and Federal brass using Frontier 9mm 124 gr CMJ RN bullets, Federal small magnum #200 primers and 4.0 grs Titegroup. I am shooting these reloads in my Ruger PC9 carbine. The fired and ejected cases are darkly colored from the mouth of the case back about 1/3 of the case length. Is that normal???