Headspace for 6.5x284 norma

[Akiona]

I have just purchased a pre-fit barrel from Mcgowen. Its a 6.5x284norma. I've been told that a 284win headspace gauge won't work from several people. Different dimensions on the norma case. Do I do it the old fashion way with a factory case with no charge in it? Not my preference. Not very precise. Any suggestion would be much appreciated.




Thank you