Butler Ford--It is true that petroleum based smokeless lubes and black powder do not go well together. If you want a lot of effort and trouble to go into cleaning your black powder cartridge firearm, just load and shoot some bullets lubed with alox, Red Rooster, or Blue Angel and shoot them with straight black powder.
I am convinced that this is why lots of folks say that black powder cleanup is hard and messy. ALL the residue left by black powder is 100% water soluble. WATER on a patch cleans black powder fouling, and nothing else is really needed. Products such as Hoppe's and Shooter's Choice will not cut the fouling left by black powder, and the creosote like residue that results when petroleum based lubes are used cannot be cut with water. The result is an unholy mess that responds only to elbow grease and steel wool.
If you use a dedicated black powder lube, it actually saponifies, or turns to a form of soap in the presence of water. This results in a clean up of one or two wet patches, followed by a couple of dry ones, and an oil patch, and you're done.
SPG is a good lube that has been around awhile. However, the best all around lube I have found is Black Magic. It was developed in Louisiana several years ago, and is especially good in hot weather. Black Magic has quite a following in BPCR in Texas, and quite a number of Quigley shooters use it. You can get it from Buffalo Arms, or Powder Inc, and Coonies. rdnck.