I've had good luck with Gatofeo No. 1 lubricant. I also only lube the first groove because the larger groove sometimes will lose half of it's lube and it throws the balance of the bullet off and ruins the accuracy.
The recipe is:
1 part mutton tallow. I buy mine from Dixie Gun Works, which offers it again after months of unavailability. This is the toughest ingredient to find, but worth the search.
There’s something almost magical about mutton tallow. It doesn’t go rancid and it really keeps black powder fouling to a minimum.
1 part canning paraffin -- the same paraffin used to seal preserves in jars, sold at the grocery store in 1 lb. packages containing four slabs. Gulf is a common brand. Hardware stores with canning sections have it too.
1/2 part real beeswax -- Beware of today's toilet seals, which are not real beeswax but petroleum-based. Get real beeswax, not the synthetic stuff. Though hobby shops may carry small cakes of beeswax, it’s expensive. Your best bet to find it will be at “Mountain Man” Rendezvous, Renaissance Fairs and from local beekeepers.
Check the net for reasonably priced beeswax. I’ve also seen it offered occasionally, at a good price, on Ebay. Can’t find a local beekeeper? Call your county extension office in the government pages; they’ll have a handle on who rides herd on bees in your area.
Toilet seals haven’t been made from real beeswax for at least 10 years, near as I can tell, and perhaps much longer. Check the label, if it doesn’t say “beeswax” it’s almost certainly synthetic and should be avoided.
All parts are by weight, not volume!
I measure out 200/200/100 grams on a kitchen scale, toss the ingredients into a wide mouth Mason jar, and set the jar in 3 or four inches of boiling water for a double-boiler effect to melt it. When thoroughly melted, mix well with a clean stick or disposable chopstick, then allow to cool at room temperature.
Do not try to hasten cooling by placing the jar in the refrigerator, or the ingredients may separate.