Originally Posted by Dave Schenck
If the bore diameter is .270 and the bullets are .277 then it stands to reason that the bullets are "squeezed" down the barrell as they bite into the rifling. Does that then mean that the SD of the bullet changes as it is forced down a slightly narrower tube on its way to the target? If we measured the bullet diameter after it was shot, what would it be?
You have got me thinking!
I believe they are talking about the rifling land versus groove diameters of the bore. For example, the groove diameter of a 300 Win Magnum is the same as the bullet diameter (.308 inches). However the rifling lands in the bore are at a diameter of .300 inches. So no, the bullets aren't swaged down by 0.008 inches in diameter, but the rifling does imprint into the jacket of the bullets. Make sense?