If the Harvester black crushed rib is loose you can step up to their smooth sabots for under 300gr bullets. If the smooths still load loose then try the red crushed ribs.
Call or email Harvester and let them know you want to try their sabots and they will mail a free sample pack to you. They are very customer friendly.
My LRH likes the red crush ribs. The knights have a larger bore than some of the other guns on the market and require thicker sabots sometimes, especially with BH209.