How to identify caliber and barrel mfg?

I have a Remington 700 short action that has been rebarreled, I originally believed it was a 6mm creedmoore but now I’m not so sure and I am either wanting to start building it or sell it and move on to another project. The only markings on the barrel are 6 CM .275 NK the problem is CM can be short for chrome moly, creedmoore or custom match. A google search of that leads me to Krieger barrels but that doesn’t give me any more info on what caliber it is. Does anyone have any ideas to help me out, is there anyway to verify that this is a krieger barrel? Or is there any measurements that I can get with a caliper that will tell me what I need to know? The bolt face would be right for 6 creedmoore also.

It's a 6mm Creedmoor. The ".275 NK" means that you must make sure that the necks of your loaded ammo are no more than .275" in diameter, otherwise you'll have pressure problems.

That diameter, by the way, appears to be the standard neck diameter for factory ammo. I think you're good to go with the rifle.

Thank you sir!