If you are having fill out problems I would recommend adding tin. What I did was add some solder, 95% tin 5% antimony. Adding more than 2% is a waste in my opinion. I have a roll of 1/8" round 95/5 solder. I add 24" to a ten pound pot. Here is an example.
These were the first bullets I cast. They are straight wheel weights with no tin addad. See how round the shoulders are? They probably would have shot ok, might have caused a little more leading but I remelted them and didn't shoot them.
These bullets were cast with 24" of 95/5 solder added to a ten pound pot. Now see how sharp the shoulders are? Much better fill out with very little tin added.
Rusty