Has anyone had experience in resizing nickle plated cases. I am specifically interested in expanding case necks from 300 to 323. I've resized brass cases up and down without problems but I've never tried nickle.

Other than standard resizing practices, just be sure and lube the inside of the case necks with a dry lube, and it will be no problem.

I personally do not like nickle cases but have used them on many occasions with no problems other than one instance when some .308 WCF brass featured necks that were thick enough as to require turning/reaming in order to function properly.

I've always made a point of avoiding nickel, and have never considered reforming nickel-plated cases. Will the plating actually conform to the re-shaping?

Never thought much about neck-turning them either. That could be an adventure.

When I first started shooting Benchrest, I shot a full length 308 with a .331 neck. I used Federal Match brass. In these days all Federal match brass was nickle plated. I never had any problems turning necks.