Helps clean the lead.
I find 800+850 degrees will pour anything I need from an aluminum mold.
Using a 10lb pot I put in a ball of wax around .400 diameter and a stir.
At that temp a flash and burn off most likely will happen. Skim.
I had a new Dragoon that was that way from the factory. Even putting pressure on the ram with it between cylinder bore wouldn't budge it. Had to strike the back of the cylinder with a hard plastic mallet to get it apart.
Once apart I inked the arbor and very minimal fine filed the contact point...
I loaded 10 cylinders. 5 with filler, 5 without. Over sealed ball. Mixed the cylinders so there was no way to know which had filler. Shot all 10 cylinders. Zero change in accuracy.
Put the powder in. Ram the ball. Seal and shoot.