Zeroing confusion

[Vince51]

Had a chance to shoot this weekend and stirred up some confusion. I recently mounted a new scope on a rifle I've had for a while. Shot two 100 yard groups to get it zeroed. It shot very well under moa. I moved out to 200 and the group drifted right about 3 inches. 500 right over 16 inches. I spent alot of time shimming to get the scope lined up with the bore axis. Scratching my head at it really. No wind was present. When I adjusted to correct windage it would move impact inconsistently to the left. It's a Nightforce nxs scope. Any thoughts?

 

[cowboy]

I would shoot it at 100 again with a large PC of paper with bull at the lower portion. Crank your turrets for a 200 yd shot and shoot at same bull. You can crank your turret to any distance - 500, 800 or whatever. If your shots are drifting right the farther out your turret distance is set I would say you have a canted scope or you may be canting the rifle. Do you have a bubble level on this scope to keep things parallel?

 

[Steyr Luxus]

"I spent alot of time shimming to get the scope lined up with the bore axis."

Just my opinion

I'm not sure why you would be shimming to do this? Are you using the Burris zee ring inserts system? Was your firearm set up level and your scope set to level prior to aligning it to the bore axis before you shimmed? Are you experiencing parallax error when looking through the scope? All of this may not be noticeable at short ranges of 100 yards. But when increasing the distance these combined errors are compounded; result you are experiencing.

 

[varmintH8R]

Sure seems like something is not lined up correctly. What kind of rings and mounting system are you using? How did you shim your scope?

Maybe this added detail will shed some light on your issue.

 

[Vince51]

I'm using the burris signature zee rings. I bore sighted the scope with the shims. trying to keep the windage centered as much as possible. I do have an anti-cant level on the scope, but I'll recheck the reticle. It's possible I moved it while torquing. I'll do some more 100 yard testing this weekend.

Thanks
Vince

 

[varmintH8R]

I would shoot it at 100 again with a large PC of paper with bull at the lower portion. Crank your turrets for a 200 yd shot and shoot at same bull. You can crank your turret to any distance - 500, 800 or whatever. If your shots are drifting right the farther out your turret distance is set I would say you have a canted scope or you may be canting the rifle. Do you have a bubble level on this scope to keep things parallel?

I agree. Run a tall target test and see what that shows you (dial 15 or 20 MOA and see if POI moves laterally at 100).

While this may be some of your issue, your results at 200 yds lead me to believe there is something else going on as well. Assuming you are shooting a moderate-velocity cartridge, I would expect you are dialing less than 2MOA of elevation at 200. To have 1.5 MOA of lateral movement would seem to be pretty extreme. It could be a combination of factors like Steyr Luxus states.

Good luck and let us know what you find.

Brandon.

 

[Eaglet]

Vince51,

I don't think canting is your problem, here is why...

To be off 3" to the right at 200 yards with a 100 yards zero, you need the scope or rifle to be canted to the right a full 40°... That's a lot and you should have seen it when you peeked through the rifle scope.

To have an idea how much 40° is, look at a clock on the wall that's hanging vertically and knowing that every five minutes tick mark is = 30°, draw an imaginary line from
about the 7 minute mark that goes through the center of the clock and you'll see
what I mean... just too much.

I would be more inclined to check the base screw holes on your action for alignment. Use just the screws, the two furthest apart, screw them in a couple of
turns and use them as sights... peek through the bore to see if they're moving in
the same direction.

If my numbers are right, you would need 0° 2' 51.89" of miss alignment to get those results... I think??? head scratching...

I can't think... Are you left handed? just a thought!

Good luck!

 

[Eaglet]

Vince51,

I guessed you solved the problem, and if you did would you share with us what the
deal was?

Thanks,

Eaglet

 

[lboom]

I had a burris scope do the same thing. After checking it all over I discovered that the cross hairs were very slowly rotating in the tube so that the cross hairs did not line up on centerline with the turrets causing a lateral shift when putting in vertical click. Just a thought

 

[Vince51]

No conclusion yet. Plan on shooting tomorrow, if the weather holds out. Bought some poster boards to do 100 yard vertical strings. Thanks for your help. Will update you all on what I find.

Vince