Reloader #7 is the most sabot friendly powder there is I set a Remington 700 ML with a McGowen .45 bbl. some years back using H-4198 and 200 gr. Hornady SST bullets. He lost a couple of deer so I switched the gun to the Pittman .40 cal 225 gr. and the Harvester lt. blue sabot. We also changed to Reloader #7 powder using 72 grains. With this combo we get 2675 FPS. and deadly accurate.
The bullet that you are using has a long bearing surface which could be causing more pressure and blowing the sabot. I have also seen sabots that were 3 or 4 years old and exposed to excessive heat fail when a fresh box would not. That Harvester sabot will blow with any bullet/powder combo when it gets to about 37,000 psi.
I believe it is the longer bearing surface causing your issue. I built a .40 cal smokeless gun last year and used the Pittman 228 gr. bullet @ 3100 FPS. with VV N530 powder. That bullet was sub moa at that speed ,but I would not get a pass through because the bullet was being driven too fast. I bought a 50 pack of the Fury 240 gr and sized them for my bore I dropped my charge 3gr.s to compensate for the heavier bullet.
With the reduced load and heavier bullet that bullet still broke 3000 FPS. It also loosened up my primer pockets on my Hankins primer modules. I would up dropping another 3 gr.s of powder to get the pressure down enough to not blow my primer pockets. I believe it was because of the longer bearing surface of that Fury bullet and not just the extra 12 gr.s of weight.