When I was a nubie I used Bore Butter because it was a TC product. Must be good? Well, I no longer use it for two reasons: 1) it is extremely aromatic. Even if you put a balloon over the muzzle your ramrod stinks and anything else that touched the stuff. When hunting I try not to advertise my presence. 2) after a period of time BB dries out and flakes off.
I have been experimenting with a mix of lanolin and beeswax. I haven't got it perfected so for the time being I use SPG.