Finally purchased my first Ruger, Stainless Steel Speed Six, 4 ". The thing is built like a tank. Much stronger than a comparable K-frame S&W ( and I own two S&W's, 28-2, 6 " and a !0-5, 4" ) I have a question regarding cleaning it. Sometime in it's life it must have had some type of rubber grip ( wood grips now). There is this black " crud " on the frame outlining these former grips ( as well as other black crud on various parts of the frame) What is the best way to get rid of it? ? Will post pictures once it's presentable. Thank you for your time and expertise.