Bore butter is TERRIBLE to prevent rust, I’ve never had much luck with it. In my early days on this forum, I tried bore butter as a rust preventative and used it for a few months. It was ok for a a month.. but after that rust started forming. Bore Butter is a great patch lube and that’s about it. I have known a few guys to use motor oil as a preservative with great results, If you do, just make sure you clean the bore out thoroughly before shooting. I myself use a lanolin based bore preservative, it’s worked well for me.