The one and only time I've ever had a patch come out of the bore with some rust on it was when I had Ballistol in it. Rifle was cleaned and dried the same as I always do and it had sat for about 3 months through the summer.
Started first using Natural Loob (hated cleaning the cooked residue back out of the bore after shooting, but never had any rust), then went to Hoppes gun oil (never had an issue with it), then switched to Ballistol because I wanted to leave a preventative in the bore when I loaded for hunting (I leave it loaded through hunting season). After discovering the rust I went to Barricade after seeing Zonie post about it. Doubt I'll ever switch, it has worked so far and I can shoot with it still in the bore with no issues.