A couple of friends own McWhorter rifles, and they shoot bugholes using the data that McWhorter provided. This may sound obvious, but the friend who purchased one firts several years ago found that not loading to the same ogive length, and just using the COAL, made a big difference in how well his shot. He copied the ammo McWhorter sent him with regards to this measurement, and did very well.
Feel free to call McWhorter. I know that both of my friends have called when they had questions, and received very useful answers right away.