Trying another sabot under similar conditions may be informative . . . maybe the slightly thicker Harvester EZ.

I've found that the Harvester "Crush Rib" and "EZ" are not interchangable. And, for the loads I use, their application is counter intuitive. The Crush Rib works best with slightly smaller, .429" bullets, like the Deep Curl, while the EZ works best with larger, .430" XTP's. It seems like it would be the other way. Go figure. It leaves me guessing.