Hey katzdad;
As I stated earlier, I'm not an expert.
To help answer your question about the bullet to rifling gap "freebore" you might find the following link interesting.
Hornady
Scroll to the bottom of the article to find your answer.
Freebore is a good thing. The accuracy can be improved or made worse by changing the AOL but as this article indicated, zero freebore can take the chamber pressure above the safe range. Keep in mind that energy is required to start the bullet in motion, then energy is required to engage the bullet into the rifling. The elapsed time is in milliseconds but trying to do both at the same time can be dangerous.
Sorry, I posted this in the other thread. It's worth repeating.