Help Identifying this Barrel

[Tennisbuff]

I am trying to identify this barrel. It's from my father-in-law's collection but he passed. I believe this this is a .308 but no markings on the barrel. Can anyone help on figuring out what this is? Thanks in advance.

[wc870]

Whats the length?

[rockrat]

Looks like an H/K flashider on it, so might be an H/K barrel for a 91 or 21

[edp2k]

Looks like HK21, which is basically a belt fed full auto HK 91 (7.62x51 NATO).
Supporting points:
1. no gas port (delayed blowback operation, not gas operated).
2. should have a fluted chamber.
3. HK style flash hider.