So i decided to cross eddie and talked Hayes the NCR guy in primm.

After i kill eddie the sarge tells me to go back to primm to talk to Hayes. But Hayes is gone. Where is he or is it a loose end?

Bump, anyone?

Hayes is apparently at a camp outside Nelson. There's a bug somewhere in there. Either he's being restationed and nobody tells you or he shouldn't be there. He has nothing for you, though.

In my game I had already finished Primm by the time I got this quest and Hayes was in Camp Forlorn Hope. I don't know if that's scripted or just a bug, but that's where I had to go to find him.

But it sounds like it doesnt matter since he cant interact with the quest at this point

The quest is over by then anyway. I've had him bug and go to Camp Forlorn Hope when I didn't do the "I Fought The Law" quest, just ransacked the prison myself not knowing about the quest. This last time I did the quest line and he stayed in Primm. However there was just a new dialogue option "The attack on the prison was successful" and he basically responds "Good" and that's it.