I highly recommend this slug mold for the .215 ish size bore guns. https://noebulletmolds.com/site/shop/bullet-moulds/224/218-25-rf-d6/218-25-rf-d6-rg4-4-cavity/
I've resized the slugs to.215 and they seemed to shoot pretty good but had to much friction in the barrel which cost vel. Your avenger uses the same barrel.