The February 1943 issue of the American Rifleman has an article on bullet lubrication.
When I read it, I was reloading heeled bullets for the .32 Long Colt for an 1892 Marlin rifle.
The article included a very old lubricant recipe once used by factories for heeled bullets. So I made some and tried it.
It worked very well in the .32 Long Colt, whether I used smokeless or black powder.
Then I used it to grease the felt wads for my .36 caliber 1851 Navy. The results were amazing. The bore had just a fine coat of ash in it, unlike the fouling I usually see with the lubricant used in commercial cap and ball wads (which, I believe, have too little lubricant to do an effective job).
The inclusion of paraffin in this lubricant results in a fairly stiff, lubricating felt wad, which I suspect scrapes out the fouling.
I tried it in my .50 caliber muzzleloading rifle, as a patch lubricant, and never had to swab the bore to fire about 35 times.
Then on to my reproduction 1873 Winchester rifle in .44-40 caliber. I used the Lyman 427098 bullet, cast of nearly pure lead, and sized to .429 inch. I used up to 35 grains of Goex FFFG black powder and the bore remained remarkably clean of fouling.
Next stop: soft lead bullets in my .45-70 Springfield reproduction. I used up to 60 grs. of Goex FFG. Again, fouling was minimal.
Then I lubricated some Lyman 358156 155gr. gaschecked semiwadcutters for my Ruger .357 Magnum.
I loaded this bullet up to 1,200 fps. No leading problems, but then the gas check surely helped.
Whatever gun I used it in, accuracy was very good. I gave this lubricant a good workout.
It closely resembles a popular black powder lubricant sold commercially.
To make it, add the ingredients to a large jar (mayonnaise size), then place the jar in a pan of water about 3 inches deep. This gives you a double boiler effect. Mix ingredients thoroughly with a clean stick (I use a disposable chopstick from a Chinese restaurant).
Allow to solidify at room temperature. If you refrigerate it to hasten hardening, ingredients may separate.
When cool, put a layer of plastic wrap over the mouth of the jar and screw the lid down tight. Store in a cool, dry place.
When you need some lubricant, return the jar to boiling water, stir, and pour off what you need.
Okay ... you've waited long enough .. here's the recipe:
1 part paraffin (I use the type sold for canning)
1 part tallow (I use mutton tallow sold by Dixie Gun Works)
1/2 part beeswax.
All measures are by weight, NOT volume.
Others have suggested adding graphite and so on, but with the kind of performance it's given, I don't think it's necessary. I just don't feel it's worth messing with success.