If your seater generates shaving from the bullet, one of two things is happening. Either the neck diameter is too tight (or chamfering is needed), or the necks have hardened to where the neck sizing process is being compromised.
The problem is springback and it works in opposite ways with bushings and sizer balls. If there's a bushing involved, the neck tension becomes reduced, and if there's a sizer ball, it becomes increased.
My .260 rounds are handfed singly, and need no accomodation for feeding in the neck tension determination. My expereince is that the best neck tension is minimal neck tension.
If I can move the bullet in the neck with a reasonable two-finger grip, I need to increase neck tension until I can't.
It's purely a practical issue, and if I could feel comfortable with less tension, that's what I'd use; but I don't like the idea of seating depths changing on their own while I'm manipulating ammo at a match.
It's not good for accuracy, and I suspect there's a safety issue involved as well.
Sometimes using a VLD chamfering tool with keep the brass from shaving the bullet.This will help your seating of the bullet consistency. Also neck tenison is usually about .02 thousandths. This is what RCBS recomends for their dies.
My 260 loaded rds. with Rem brass also measure .291. I have a custom Forester die with a .289 neck and a redding bushing neck die with a .288 bushing. The .288 neck bushing is set to size 3/4 of the neck and shoots 1/2 moa at 600 vs. 1 moa for the .289 die. .288 is not too much. The stock forester die I think comes out about .285 without the neck expander ball and this did not shoot bad.