Rifle Scopes Scope zero shift issue

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Feb 14, 2017
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#1
I have a bushnell dmr that seems to shift zero when the gun is jostled around. It will hold groups and track out to 1000 and back. The issue lies in transporting the scope, or just picking it up and bouncing the gun off the butt. Then the zero shifts 2" vertical and 1/2" horizontal. I have tested it on 2 guns. Seems repeatable. I have tested the same guns with an 2 other scopes, and it does not seem to happen. I switched the rings, and it seems to be the same.

Now for the dilemma. I sent it to bushnell and they sent it back saying there was no issue. I do not know if they misunderstood, or if i missed something. Ideas?
 
#4
koshkin said:
What kind of bases and rings are you using? I've seen this kind of stuff happen when the recoilkey of the ring was not engaging the base consistently.

ILya
Click to expand...

Seekins/ vortex rings and utg pro rings. I shot it in both sets of rings. on a custom .280 ai and a .243. I was moving on both guns. The only thing i can think is maybe i am not getting the same body position everytime, except i dont have the issue with my other scopes. It does not shift if i shoot, then get up and move around, then shoot again. It only seems to be when jostled. But i will check the ring mount, maybe they are not getting good contact on the rail.
 
#5
When you mount the scope on the rail, do you make sure that the rings are pushed all the way back to make contact with the base? the rear flat of the recoil lug inside a cross lot has to make contact with the front flat of the rail.

I have not used UTG Pro rings, but I have a fair amount of mileage with Seekins rings and they work well.

It is really weird if it shifts when you move the gun, but does not shift under recoil. It is possible that it is the scope, but it does not sound likely.


ILya
 
#6
koshkin said:
When you mount the scope on the rail, do you make sure that the rings are pushed all the way back to make contact with the base? the rear flat of the recoil lug inside a cross lot has to make contact with the front flat of the rail.

ILya
Click to expand...

Maybe I misunderstood your post but to clarify. Rings should be pushed forward so the front of the bar contacts the rear of the rail. This helps prevent movement under the time of most stress, which is recoil. Newton’s 1st law.

Or maybe I’ve been wrong from day one.
 
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#7
RampedRaptor said:
Maybe I misunderstood your post but to clarify. Rings should be pushed forward so the front of the bar contacts the rear of the rail. This helps prevent movement under the time of most stress, which is recoil. Newton’s 1st law.

Or maybe I’ve been wrong from day one.
Click to expand...
You are correct. I was thinking one thing and typing another.
 
#8
I would also pull your rings and check the crossbar on the underside of the clamp for impact marks. I just had a new set of Vortex PMR rings which are Seekins rings with the Vortex name on them, and a new Vortex AMG that was having unexplained shifts in POI. I sent them back to Scott Parks at Vortex and the scope checked out perfectly but the rings were out of spec. The aluminum ring side of the clamp to the rail was fat so when the torx screws were tightened, the clamp was clamped to the aluminum ring and not transferring force to clamp to the picatinny rail. Only one ring of the pair had this problem but it was enough that my scope was not holding zero. It would be fine for a while then for no reason would shift.
IMG_2369.jpeg
 
#9
I've had this issue with every scope I've mounted on my Tikka rifles. Always assumed it was normal to continually re-zero. Like you, my zero does not move during a range trip typically, but it's never right before I start shooting.

I've always used EGW or Tikka factory base (CTR comes with a base) and SWFA rings. I may need to do a mount upgrade. I had this issue on my Ruger 10/22 as well until recently when I replaced the base/rings with a DNZ one-piece mount, and the issue went away entirely.

I'm not rough on my guns at all. They go in the safe, into a soft case for the range, get cleaned when they get home, and then go back in the safe, all very gently.
 
#14
Rings
patriot07 said:
I've had this issue with every scope I've mounted on my Tikka rifles. Always assumed it was normal to continually re-zero. Like you, my zero does not move during a range trip typically, but it's never right before I start shooting.
Click to expand...
Curious why anyone would think having to continually re zero would ever be normal? If you haven’t changed loads your zero should stay the same that is unless your zero is beyond 100yards, which is dumb.
 
#18
I have 5 sets of Seekins rings and the only one I've had any issue with was the one ring that I bought with my AMG. Vortex diagnosed the issue and sent me a new set of rings which are fine. I think Seekins are one of the more affordable rings that work very well. I also have two sets of TPS rings and they are also one of the lower priced rings but have worked very well for me.

Both my Seekins rings and my TPS rings have upper end scopes in them from the Vortex AMG, to S&B 5-25, to Kahles k624i. They have been removed from their rifles and remounted with no more than a tenth mil or two of adjustment needed when remounting. They have also had their scopes removed from the rings and remounted and none of them have marked the scopes that were mounted in them. I don't lap any of my rings and consider them to be excellent rings.
 
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#20
patriot07 said:
Because I'd never experienced anything else.
Click to expand...

That is not normal.

Aadland engineering 30mm rigns are excellent in my practice.

Kelbly makes very high quality rings that do not get a lot of publicity.

The rings I have been using the most lately were Burris XTR Signature since I make good use of the plastic inserts. They have been working exceedingly well for me and they are reasonably affordable.

ILya
 
#21
Are you mounting/torqueing everything to specs?

Have a friend mount it on their rifle to specs and see if they experience the same shift.

I made the switch to spuhr. I've taken the mount off for several reasons ant its always reliably returned to zero or very close.
 
#22
Thanks for all the responses. I'll see if I can find a palatable path to a ring upgrade. I figured the SWFA rings would be fine for a braked 6.5 CM. They seemed identical to the Burris XTR for about half the price when I bought them several years ago.

Mine is usually close to zero, but almost never at zero in either elevation or windage. Not uncommon at all to be .1-.2 mils off in both axes. I'd love to not re-zero every time I go to the range.
 
#23
patriot07 said:
Thanks for all the responses. I'll see if I can find a palatable path to a ring upgrade. I figured the SWFA rings would be fine for a braked 6.5 CM. They seemed identical to the Burris XTR for about half the price when I bought them several years ago.

Mine is usually close to zero, but almost never at zero in either elevation or windage. Not uncommon at all to be .1-.2 mils off in both axes. I'd love to not re-zero every time I go to the range.
Click to expand...

The original XTR was a fairly mediocre ring. XTR Signature is a different ballgame altogether.
 
#26
Could also just be that you’re in a different position in a different day and the recoil and you aren’t jiving the same. Sometimes I’ll notice that I’m a hair over but I readjust and get the rifle pointed straight naturally and it goes back how it should.
 
#27
spife7980 said:
Could also just be that you’re in a different position in a different day and the recoil and you aren’t jiving the same. Sometimes I’ll notice that I’m a hair over but I readjust and get the rifle pointed straight naturally and it goes back how it should.
Click to expand...
That's possible. I've definitely noticed a POI shift when I load the rifle differently. But I'm shooting off the bench 9 times out of 10 and I do try to have good, consistent form.

I noticed the same issue with my Ruger 10/22 using the factory rings - zero would move all over every time out to the range. Got a DNZ one-piece mount and the problem went away entirely.

I got some seekins rings with the ebay 15% off coupon last night, so hopefully we'll figure out if it's me or the gun.
 
#28
Also make sure you are degreasing everything when you install your mounts. Most rings come with plenty of oil on the screws to prevent rust in packaging. They should be dry when installed, or a little blue loctite, but definitely no oil anywhere.

If you are using quality mounts that were installed per the instructions and still having issues, I'd be suspicious of the scope.
 
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#29
patriot07 said:
That's possible. I've definitely noticed a POI shift when I load the rifle differently. But I'm shooting off the bench 9 times out of 10 and I do try to have good, consistent form.

I noticed the same issue with my Ruger 10/22 using the factory rings - zero would move all over every time out to the range. Got a DNZ one-piece mount and the problem went away entirely.

I got some seekins rings with the ebay 15% off coupon last night, so hopefully we'll figure out if it's me or the gun.
Click to expand...

If you don’t have one already, get a wheeler fat wrench torque wrench. Before and after your range session make sure it’s still clicking at the desired torque for your ring and base screws.

If you are able to torque them at anytime, something is backing out. Either needs degreasing or loctite(blue).

It literally takes more time to set the torque on the wrench than it does to verify the screws.

Also, make sure you are pushing the mount/rings all the way forward when you install and torque.
 
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#30
Dthomas3523 said:
If you don’t have one already, get a wheeler fat wrench torque wrench. Before and after your range session make sure it’s still clicking at the desired torque for your ring and base screws.

If you are able to torque them at anytime, something is backing out. Either needs degreasing or loctite(blue).

It literally takes more time to set the torque on the wrench than it does to verify the screws.

Also, make sure you are pushing the mount/rings all the way forward when you install and torque.
Click to expand...
I am an engineer, so I have a torque wrench (3 or 4 IIRC) and I have re-checked torque a number of times on it. I used blue Loctite when I put the scope on, and haven't had any of the screws back out.

Never heard of pushing it forward when you install the rings on the base? Makes sense, but this is the first I've heard of that. I did it when I installed the new Seekins rings last night. Hopefully these are worth the $.
 
#31
patriot07 said:
I am an engineer, so I have a torque wrench (3 or 4 IIRC) and I have re-checked torque a number of times on it. I used blue Loctite when I put the scope on, and haven't had any of the screws back out.

Never heard of pushing it forward when you install the rings on the base? Makes sense, but this is the first I've heard of that. I did it when I installed the new Seekins rings last night. Hopefully these are worth the $.
Click to expand...
if you dont push forward while installing and tightening the rings, they will move under recoil. by pushing them all the way forward, there is no place to go.
 
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#33
Makes sense, but I haven't had any problem with the zero moving during the day. I've had issues with it moving between range sessions.

Either way, hopefully the better installation practices and better quality rings do the trick.
 
#35
Not uncommon at all for mine to shift .1-.2 mils in both windage and elevation. Sometimes more, sometimes less.

It's generally pretty easy for me to dial out parallax on my SWFA HD 5-20. I don't think that's the issue.
 
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