Chris,
What type of BP grease/lube do you use?

Another theory I have is that using antisieze for a BP lube may allow some of the antisieze to get into the combustion chamber area and help keep the crud ring from forming, at least not as bad. It doesn't seem to have as much credability as the BP design theory though. The BP blowback would have a similar effect as the lower power primers in that it would also tend to allow the primer pressure to leak as well.

Then again, maybe you got lucky and your rifle just likes the stuff. My Magbolt sure does. My son's optima even gets a crud ring with BM3 just not as bad as 777.