Oldbloke wrote:OK. I will ask the question. Why filler? Are these very light loads?
Yep, it's used to fill the void in BP cartridges which aren't filled to capacity.
(
There is a little bit of debate on this, but it's widely accepted that) there should be no gap between the powder and bullet when filling black powder cartridges. So if you want some reduced loads you need filler.
It's a bit of a pain working up black powder cartridges as the filler effectively effectively reduces the case capacity. Unlike a smokeless cartridge where the capacity remains the same and you just increase the powder charge from lower to higher, with a black powder cartridge your changing two things at once which effect pressure and need attention.