I will make this as short as possible, then if you need more info I can add what I know.
A fellow that I have known for quite a while had some luber sizer problems last fall. He wanted me to lube some of his Postell's for him. So I did, only I used FWFL. He said everything was fine, no fouling or problems in that area. He had been using some fellows lube with moly , gents name slips my mind now but he is the supposed BP go to person. Lee Shaver, just remembered.
The FWFL lubed bullets grouped well but were way off from his previous sight settings. I had concerns that maybe my batch of lube would be a bit hard, but I PM'd felix and we thought they would work OK.
I think he said that the groups were running low and right, I don't remember for sure. I didn't think lubes would have that much effect on the way the rifle grouped?
BTW, it is a Shiloh if that helps you any. I used his sizer die and top punch, .458 I think is what it was.
I am ignorant in the workings of BP cartridge rifles other than what I have read. No hands on experiance. I thought maybe my batch of FWFL would not keep the fouling soft, but he was pleased with that part of it, cleaned up pretty easy he said.
Any thoughts or ideas are appreciated.