It would be hard to tell if the bullet moved to seat against the rifling depending on the neck tension. Why not seat a bullet in a normally sized case and look at engraved marks? Steel wool the surface of the bullet, the marks will be easily seen. Then progressively seat the bullet deeper till the marks are barely visible. You can reference from that and seat from that distance. To be frank there is no magic place to seat a bullet. You read of guys saying they prefer to start .010" or .015" away from rifling but the actual distance can vary.
Try your pet distance fromn rifling then do a series of bullet seating depths in small increments to try and find the best spot.
One time I took a 308 win and progressively moved the bullet deeper into the case in .002" increments to show a friend there can be more than one sweet spot. How far were they from the rifling? Don't know as I didn't use a stony point tool. Just referenced from small rifling engraving marks backwards. (ignore the numbers they were some sort of reference for me which I have since forgotten)