The Nordic design does not use a barrel collar. The bolt face of the Nordic pattern bolt butts up against the barrel and is a self contained unit. Nordic, JP, RRA and DPMS Gen II use this pattern of bolt and barrel. The barrel of the Nordic is patterned where the ejector is attached to the side of the barrel. The CMMG bolt reciprocates on rails and the ejector is incorporated in the rail.
The closest design to the Nordic is the new BCA dedicated side charging 22 LR. The pattern of the BCA bolt is very similar to the Nordic pattern bolt.
Unless your a machinist who can turn a barrel blank into a desired Nordic barrel it would be cheaper to buy a CMMG pattern bolt and barrel from RTB or buy a BCA.
Here is a picture of Nordic pattern bolt and schematic I got off the Nordic site.