Unknown Steve Kostanich Cartridge on .30 Caliber - Please help

[JustAnOldCoot]

Hi fellow OCD's...I purchased at auction a couple of Steve Kostanich's former F-class rifles...both of which the cartridges are a mystery to me.

One of them has some cerasafe chamber dimensions that I can't find a match for - appears to have a 30 degree shoulder, neck length of about .402, shoulder height of about .145, case diameter of around .460, and overall case length somewhere around 1.852".

The barrel is marked with Steve's Name on one side, and (HC 30x2" .332" NK) on the other. Clearly the neck dimensions are a giveaway...but the HC 30x2" has got me puzzled. Please see the attached photos - any information you have would be greatly appreciated. Take care and God Bless you and yours...