You may find the bullet and sabot combo might effect the POI shift, in regards to clean or fouled bore.
My experience with of shooting the 250gr TEZ, for instance, I could not get a consistent clean bore first shot. Not only was the first shot 3-4" higher at 100 yds on a clean bore compared to fouled bore, I was also experiencing left or right shifts in POI.
Now shooting the .430 XTP's, both 240 and 300gr, I do not get any POI change from clean to fouled!