I'm sorry about the shortness of my angry answer. I tend to get a little bump up in blood pressure whenever I have to answer for the wisdom of ignorant interlopers who pretend to be LBT.
My answer was correct, but there are variables which prevent lube from working. If the bore is extremely rough, or just a little rough when shooting plainbase, specifically on the leading edges of the rifling, this roughness can act like a file and strip lead away. When some lead gets stripped away, or wiped back into the grooves because of excess drag against the bearing along the rifling edge, a space forms on the non driving side of the rifling, which allows lube to squirt forward, losing the hydraulic lube pressure required for good high pressure load performance. Sometimes softer bullets will partially solve the problem, by reducing leading, but it it does, you'll have a very narrow pressure window to work with, i.e. a very precise powder load will probably be required. And accuracy will never come up to what could be if things were right, meaning the bore were lapped or a quality lubricant was used. Regarding this last statement. If the problem is happening with any lube beside LBT, give one of ours a try. It normally fixes the problem if the rifling edges aren't extremely rough.
