This is what I have, maybe it will make some sense. The inner diameter of a fired case neck is .315-.317. The outer diameter of the same neck is .340-.343. The latter number is maintained forward of the case where the bullet resides. I can confirm this by measuring the lead slug, which gives .342 +/- .001. It then tapers down in size until it forms the lands and grooves of the rifling, which results in .313 groove and .300 land. I might need to take a pic of the slug. It will be easier to explain. Finding the right bullet to fit the groove diameter and provide sufficient weight has been a chore. What I am seeing (though possibly in error)with large throat numbers only makes the bullet hunt more interesting. Thanks.