This is one of those things that may be more theoretical than practical. I've shot many a cast bullet with the base well past the neck and still gotten good accuracy. Would I have gotten better accuracy with the bullet within the neck? I dunno. If I coulda done it that way, I woulda.

This is not real testable. You would always have to introduce another variable to test it. Even if you did extensive shooting with one bullet in a short throated rifle and then rethroated it, you would have altered usable case space and would have the possibility that the new throat was better or worse than the old one.

Thanks for your reply. Maybe I should also note that this question pertains to practical accuracy for hunting--not target or silhouette.