I think the problem is more likely to do with the splines of the collet jamming in the body of the die. As the case is withdrawn the collet does not release the case adequately - hence mandrel may scratch. Try dismantling the die and clean/polish the splines to prevent sticking.

Regards

Titan

I have a big pile of Federal 470NE nickel plated cases. I haven't fired any yet, but I"m wondering how the nickel plateing will hold up to repeated sizeing? I annealed the case necks to start with. Hope this will work.

Same thing happened to my Lee 7mm mag dies after I ran some unfired nickel plated brass through them. There was nickel plating on the inside neck, and it flaked off when neck sized. I think I read how nickel flakes will embed into the seated projectile. You can guess what might happen to a barrel when you fire the rifle. I'm pretty sure fire-lapping calls for a soft lead bullet coated in a mild abrasive.
I'm not sure how hard the nickel plating is in relation to steel dies, chamber throats or quality barrel steel, but I don't think any of these items were designed to withstand repeated nickel flake abrasion.
What's all this blaming Lee dies anyway?
Regards, Cheeky.

I prefer to reload brass in general but I think this problem is more an illustration of my problem with Lee dies. They have some tremendous designs but are often made of inferior material. It seems to me the Mandrel should be made of hard enough steel that it wouldn't so easily scratch......DJ