James V. Howe, co-founder of Griffin and Howe, had the following to say about olive oil in his Modern Gunsmithing, Funk & Wagnalls, New York, New York, 1934, Volume I, p 342- (1941 printing)
"This oil is totally unsatisfactory, for it not only has a bad lubricating quality, but will rust and spoil any gun parts to which it is applied."
I don't know what is in Bore Butter®, but a thorough hot water cleaning, with or without soap, failed to remove a hard brown deposit that was clearly visible with a borescope from the barrels of my muzzleloaders. This happened consistently with two out of the last three lots of Bore Butter® that I purchased. If the deposit was not promptly removed, light pitting followed quickly, despite use of sperm oil in the bore. Removal of the pitting necessitated unbreeching the barrel to lead lap the bore.
The hard brown deposits can be removed by use of Iosso bore paste and lots of elbow grease. Once these deposits are removed normal oiling will protect the bore.
regards,
Bob