Murphy's Oil Soap, Leighton. It is a vegetable based soap. Don't know if that matters or not, but it has worked for me for a long time.

No rusting problems. However, I remembered that I omitted mentioning a step in my cleaning process. After the mixture is used and the bore is dried with patches as much as possible I drench the bore with a moisture displacer like WD 40. I then dry it again and use the RIG.

Sorry I forgot to mention that.

SRH

May God bless America and those who defend her.