Lube groove depth is not a factor with black powder, or plainbase with smokeless. Also, gas checked bullets are not confined to only smokeless loads. They do wonders with black powder also. However, when bullets are designed for blackpowder, AND USED WITH THE PROPER LUBRICANT, the low velocities produced with black, and the lubrication value of the blackpowder soot COMBINED WITH A LUBE THAT KEEPS IT SOFT AND SLIPPERY, gas checks aren't needed.
Unless told that a bullet will be used for black powder, I set them all up for smokeless. Many LBT bullets, reguardless of nose profile work great with black powder, but those with minimum lube space don't.
The key to black powder performance is to get lead off the barrel with lots of lube groove space (not depth). Any reasonable groove depth is fine so long as it is deeper than the rifling grooves. Some people have reported excellent results using LBT Blue Soft lubricant with black powder, but I don't reccomend it for that. The best black powder lubricants I've heard of are called Wonder Lube, which is a trademark name, but marketed under several labels. I think Ox Yoke the is manifacturer of all of them, but may be wrong on that. If the label says it is for black powder and it is called Wonder Lube, it is the right stuff.
Try what ever LBT bullet you have with this lube and black powder. If you get fouling, try softening the alloy. But hard alloys are best, same as with smokeless, if the bullet fits the gun properly.
If you order a mold from LBT with intentions of using it for black, tell me when you order and I'll set it up right. It will work fine with smokeless too. --- If you don't ask, it may not work well with Black powder
