I would say it is definately the sabots. My guess is that you are using the sabots that come with the PR QT bullets. If I am not mistaken these are Harvester sabots. Havester sabots, from my experiences, are much softer than MMP sabots, and will not hold up as well to higher pressures, velocities, and heat as well as the MMPS sabots. You may want to give MMP hi pressure or Hornady (made by MMP) hi velocity sabots a try.

As the temps outside climb into the upper 80' s and 90' s, any sabot tends to become soft and pliable. Ramming them home in a hot barrel doesn' t help them any either. Let your barrel cool (as much as possible) a few minutes between shots, take it off them bench top and direct sun light, and place in in the shade for a few minutes. Also, to help keep my sabots in a semi cool and much tougher state and ready to shoot, I carry a small beverage cooler with me to the range. In this small cooler I keep a couple froozen blue ice packs and I place my sabots and bullets on top of the ice packs. This keeps them cool and tough for good accurate shooting.