I finally got a suppressor in, so I decided to thread my remmington 700 sps 26" bbl with 5/8x24 threads as that is what the suppressor uses. After taking it to the range today, the rounds I previously had it zerod for (168 grain federal gold medal match sierra match kings) were shooting about 3 feet to the left, I cranked the scope as far over as I could and was still about 8 inches from the target, still to the left. Suppressor I am using is a YHM resonator. The ammo seemed to still being shooting hard left even without the suppressor. Is this normal for having threaded the barrel? anything to trouble shoot the problem and get them on target?

Who did the threading? How was it done? Was the crown touched?

When the threading was done, was there optic re-mounted the same? I have seen a color of occasions where flipping the orientation of the rings on the rail will drastically change horizontal position and availability on the scope. Those rings got replaced.

No, 3' POI shift is not normal.

26" is a loooooonnnnnnggggggg barrel to ad a suppressor to.  Wouldn't be surprised if the harmonics are wildly off with that extra weight on the muzzle.  

Did the POI shift without the suppressor?  Are the threads concentric to the bore?  Crown got a ding on it?  Are you striking any baffles?  

3" is expected POI shift, but 3' is insane.  Something is definitely wrong.

Put the can on and look down the barrel from the chamber end.  Can you see the inside of the silencer on one side or the other?

I had a marlin 357 do the same thing. No explanation. Checked all of the above.

The only time ive ever seen a shift that extreme from from a bullet just grazing a baffle as it came out.

Hi, I just took it out again today, I was getting about 1.2 inch groups at 100 yds after rezeroing the rifle without the suppressor, but then when I put it back on, once again it was shooting 3 feet left and 1 foot down. threads and everything are concentric, no baffle strikes to be found

the suppressor and holes are concentric, I can't see either side of the suppressor when looking through the chamber side

none of the baffles, nor the end cap have been grazed at all, the baffles are all clipped down the line, maybe it's pushing the air in a weird way to the side when it is leaving the barrel

Is the impact with the can off in the same general area as with the can on, but with a few inches of vertical?

It almost sounds like the barrel was warped during the process, but not warped due to the actual threading.

Who did the work? Was it a well known or experienced smith?

As an experiment, try getting a shim like you'd use to time a mount and see if indexing it will impact POI. Also if you have a cover on there try with / without that. If you can get it to shoot predictably 36 MOA up you'll be golden at 1000 ;)

Also take a picture of the threading and share it.