Member Lewis speaks from experience. He says it right too (hat-tip).

Some shooters don't realize that those round 'fiber woolies' that you seat between the powder and bullet (even MMP sabot) work fantastic. If you can't find any, use the wife / mother's corn meal instead. Can be put in a powder volume measurer too. Can't remember specifically, but I think I used around 20gr.

Just about everyone using conicals in fast twist modern MLs find varying success with the Heavies (+400gr conicals)).