I've always seen dire warnings against use of any petroleum product that will come in contact with burning/burnt black powder.
Lately I've been seeing reports from some folks saying they have had no problems with it, or that it's fine as a bore protectant if you clean it well before shooting,,,, but some people's idea of "works fine," or, "not a problem," is different than others.
I do know that someone I trust based on his repeated, and demonstrated, results uses only animal amd vegetable fats in his guns and has no rust or other issues even after leaving the gun dirty a day or two, sometimes it's been fired and reloaded then left a day.
Personally, I try to stick with food grade/food safe stuff for my patch and wad lubes,,, I don't shoot conicals from my muzzleloaders so don't have experience there but if I did I don't think I'd worry as much about it. If I were to go that route and was to use it for hunting I think I would seek a combination of mink or neatsfoot oil and beeswax, or coconut oil and beeswax. The coconut oil is pretty much solid, but not hard, up to about 70°f and thr mink oil is a fairly solid grease too, not sure the melting temp, this might be beneficial with a bullet lube.