Opinions -- Rifle stopped grouping

[sjvcon]

Have a Fierce CT Edge.  6.5 Creedmoor.  Put a Nightforce NX8 on it...proper break in and cleaning.  Once it was broke in it shot several factory loads sub half-moa.  I was very pleased.  Needed the scooe on a backup elk rifle last year, so pulled it and ended up liking it on that rifle.  Bought another...same scope but used for the Fierce.  Mounted and shot...no longer liked several of the loads it did prior.  Did okay with a couple Berger loads at 100yds...but never like before at 200.  Always opened up some.  Took everything apart (e@cept pulling barrell) and built it all back up...everything tighened to specs and licktighted.  Even lightened the trigger.  Went out today and it was terrible ... just as bad as the last range trip.  I am thinking it's the scope.  If I said I shot groups the size of a half dollar at 200 with the 1st scope I am not lying.  Befire I pull the scope and try another I figured I'd get opinions.

[CouesPursuit]

Have you thoroughly cleaned the barrel, especially for copper fouling? That or try another scope?

[Red Rabbit]

Put the original NF back on and recheck groups.  My hunch is that it is the used scope.

[sjvcon]

1 hour ago, CouesPursuit said:

Have you thoroughly cleaned the barrel, especially for copper fouling? That or try another scope?

It's been cleaned more than once.  And yes, for copper fouling.  It's plenty clean.

[sjvcon]

1 hour ago, Red Rabbit said:

Put the original NF back on and recheck groups.  My hunch is that it is the used scope.

That's what I'm thinking.  I hope if it is the scope Nightforce can repair it.

[IA Born]

2 hours ago, Red Rabbit said:

Put the original NF back on and recheck groups.  My hunch is that it is the used scope.

Exactly what I was thinking.  Most every time I've had this happen, it was a scope issue.  Sometimes, scopes get dinged in transport or its a "Monday morning/Friday afternoon" product.  I'm guessing NF will honor it and repair it.   Good luck.

[PRDATR]

What Doug said. 

[Red Rabbit]

Were you able to swap scopes and retest?

[Big or Bust]

Optics or mounting system...

[L Cazador]

Nightforce will fix the scope if that what it is, no problem. A simple check is to shoot a square and see if the adjustments are accurate. Most likely it's a bedding problem if you took it apart and it got worst. Also it could have a severe carbon build up in the throat so the more shots you shoot the worst it will get. Unless you have a bore scope you won't see it. I'm going to guess that's what the problem is. How many shots down the pipe? Are you using a carbon remover like Bore Tech C4? Are you using a brush or patches?