Gentlemen: I have mounted scores of scopes over the years. I would like to think I have it down pretty good, as I have never --until now- had any issues at all.    That being said....

 I recently took a  Springfield Armory 6X24 Government Model I have had on this particular rifle for the last 15-18 years (and has performed famously!!). I  replaced it with a Nightforce ATACR 5x25.  The rifle is a Remington PSS (.308), factory barrel and trigger, with a D.D Ross (20MOA) one piece base. I left the rings on the SAI.  The day before I removed the SAI scope, I was dinging 600,700,800, and 900 yard steel with relative ease. That combination has worked flawlessly for well over a decade.   

When I installed the ATACR, since it is a 34mm tube, I had to run to the local Sportsmans Whorehouse and grab a set of medium height rings. Warne rings were all they had in that diameter. 

I mounted everything as I have done numerous times before, and went out today to zero it. At 50 yards, as I was bore sighting  the old fashioned way (no lasers), I learned right off the bat I could not adjust the elevation low enough , AND  it was almost all the way to one one of my windage adjustment!!!   I did check the Zero-Stop and eliminated that as a reason.

I would like to think a pretty fancy scope like a Nightforce ATACR would NOT be the issue. From what I have read over the years, the D.D.Ross base is top quality, and I have read really good stuff about the Warne rings. And, to weird things out, as I mentioned, the rifle was shooting fine before I took the scope off.  

Where did I goof up?  Could it be possible I don't need a 20 MOA base since the ATACR is supposed to have a butt-load of elevation?  But that wouldn't explain my windage issue.

 Something is not right, but for the life of me.....I can't figure out where.

Original Post

Could the centerline of the rings not be true as mounted?

Maybe try a different set of a different manufacturers rings for shits and giggles?

I won't insult you by asking if the mounting surface of the base and the mounting surface of the rings were clean and burr free.

Have you tried an alignment tool?  This one is for 1" and 30mm, but there are 34mm versions out there.

https://www<dot>sinclairintl.com/optics/optic-accessories/mounting-tools/sinclair-scope-alignment-tool-prod36960.aspx

Mount the centers in the rings point to point and see if they don't line up dead nuts.

------------------------------------- "A True Warrior knows neither Left or Right"  Looking for a doc who can fix my allergies.. Stupid People and IED's...

Nightforces's website isn't cooperating with my iPad, but it sure seems like your scope has plenty of elevation to completely negate the base angle.

Perhaps the large amount of elevation adjustment isn't equally shared between up and down?

Again,  this isn't my area of expertise. 30mm main tubes were still hot shit the last time I was shopping for high end glass. 

I took everything apart, cleaned it all, and put it all back together. (Nothing looked overtly wrong.) In a visual bore-sighting, at 100 yards I am about one foot low with the elevation cranked all the way down.  (I fully understand a visual bore-sighting is one step above useless.)  I did however perform a very unscientific and/or reliable inspection test-  I draped a plumb bob over the top of the scope up towards the front and measured horizontally to the barrel. a little over 1/16" difference!!! I could see had I compared the difference in measuring the distance from the side of the scope to the stock would involve any differences in the stock dimensions,  but I went to the barrel instead.    

.........why can't anything I ever own or work on go right just one fuckin" time.....................

I had a 700 PSS action with the scope mount holes bored way off-center.  The Leupold M1-16X windage was all the way to one side.

The USAMU bolt gun gunsmith welded up the holes and bored new ones true to the bore and face of the action.  Fixed that right up, but left a bad taste in my mouth about Remington's QC (this was a late 80s - early 90s PSS).

Which Warne rings did you get? Horizontal or vertical split rings?

Frank Galli from Snipers Hide said he’s seen issues with vertical split rings affecting scope tracking and performance. 

Here’s someone on the  snipershide.com forum that seemed to have the same problem as you using Warne vertical split rings: 

http://forum.snipershide(dot)com/threads/vertically-split-rings.6878478/

Yeah, but for the life of me I cannot figure out why or how-specifically.

I removed the rings and base,  cleaned  everything. I started replacing things, starting off with the  D.D Ross base.  I plopped on a one piece base base (of forgotten manufacture) and put it all back together.  If that didn't work I had another set of rings on hand. 

   Whatever the problem was- for some strange reason it must have been related to the base as once I re-assembled it, I visually boresighted it, and shot a group alarmingly close to point of aim, with plenty of adjustment left in every direction.

Strange, since the initial combination was shooting famously.

Sinister---Keep in mind I spent decades standing over a lathe, milling machine, etc, - with absolutely zero NC or CNC stuff- all hand's-on machinist stuff), using mic's down to the .0001 and kinda know my way around checking stuff like this.  I made four threaded "studs" -paying close attention to accuracy with the OD of the stud in relation to the threads I put on them--and after screwing them into the receiver holes where the base is supposed to attach to, I checked the alignment of those fours hole in relation to the chamber/bore.  Pretty easy to do, I used a piece of drill rod to make an insert the size of a .308 case with a shank about 6" long behind it.   I stuffed it into the chamber, then ran a dial indicator along the shank and a straight edge along the four 'studs" sticking out of the top of the receiver. (Luckily, all four of the studs were right on the proverbial money in relation to each other, so at least THAT part wasn't a problem.   If they were going to be off, they were ALL going to be off.)   I then compared the shank to the straight edge above- and there was damn-near no runout.  (Well, within .0007)    Yeah, surprised the livin" shit right out of me!!  I would have figured way more than that.

 

Oh well, it's shooting like it's cool. I got it zero'd at 100 yards, and was dinging steel way out there again. I sure do like them thar' ATACR scopes!!!   Thanks for asking. (And I suppose I should have informed everyone that was losing sleep over this as soon as I got it taken care of. )

Bill, Idaho posted:

Yeah, but for the life of me I cannot figure out why or how-specifically.

I removed the rings and base,  cleaned  everything. I started replacing things, starting off with the  D.D Ross base.  I plopped on a one piece base base (of forgotten manufacture) and put it all back together.  If that didn't work I had another set of rings on hand. 

   Whatever the problem was- for some strange reason it must have been related to the base as once I re-assembled it, I visually boresighted it, and shot a group alarmingly close to point of aim, with plenty of adjustment left in every direction.

Strange, since the initial combination was shooting famously.

Sinister---Keep in mind I spent decades standing over a lathe, milling machine, etc, - with absolutely zero NC or CNC stuff- all hand's-on machinist stuff), using mic's down to the .0001 and kinda know my way around checking stuff like this.  I made four threaded "studs" -paying close attention to accuracy with the OD of the stud in relation to the threads I put on them--and after screwing them into the receiver holes where the base is supposed to attach to, I checked the alignment of those fours hole in relation to the chamber/bore.  Pretty easy to do, I used a piece of drill rod to make an insert the size of a .308 case with a shank about 6" long behind it.   I stuffed it into the chamber, then ran a dial indicator along the shank and a straight edge along the four 'studs" sticking out of the top of the receiver. (Luckily, all four of the studs were right on the proverbial money in relation to each other, so at least THAT part wasn't a problem.   If they were going to be off, they were ALL going to be off.)   I then compared the shank to the straight edge above- and there was damn-near no runout.  (Well, within .0007)    Yeah, surprised the livin" shit right out of me!!  I would have figured way more than that.

 

Oh well, it's shooting like it's cool. I got it zero'd at 100 yards, and was dinging steel way out there again. I sure do like them thar' ATACR scopes!!!   Thanks for asking. (And I suppose I should have informed everyone that was losing sleep over this as soon as I got it taken care of. )

Seven tenths runout. Yeah I’d say you’re good to go. Most people only get it that good by accident.  I do have some parts at work for our units that require two tenths runout. 

Mojo/Mark
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Joined: 9/30/09
Location: Northern Nevada (Reno/Sparks)

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