New 6.5 Grendel build...
-Odin Works barrel & bolt (came as a kit).
-New Manson Grendel headspace gauges.
-Bolt does not close on no-go gauge (un-mounted barrel, extractor & ejector removed from bolt). As expected.
-Also does not close on go gauge. Lugs lock a bit but don't rotate into battery.
-Bolt closes on a Hornady cartridge easily with or without extractor & ejector.
-Odin works advertises as SAAMI chamber. Manson says their gauges are also SAAMI.

If it were excessive headspace I'd be more worried. Odin Works support says it should be GTG.

Would you feel uncomfortable putting this barrel into service?

Not at all. It's at minimum headspace, less maybe a half thou, which will go away in a hundred rounds or so as the lugs wear a little.

It's fine. Shoot it.