If a scope won’t hold zero

[redneck2]

Question (theoretical). Suppose I have a scope that shifts zero. Could I check it for defects by maybe locking the gun down solid, moving the reticule maybe a dozen clicks one direction horizontally, a dozen one direction vertically, then move the exact opposite amount to see if it hits original zero?

Just wondering if that would weed out a shifting POI.

 

[earlthegoat2]

If the POI shifts around without making adjustments, it will not correct itself by making adjustments.

Either the scope won’t hold adjustment or there is play on the mounting system.

 

[redneck2]

You’re missing the point. Can you hold the rifle solid, adjust the scope a known amount, then try to return it to zero.

If the scope is defective, will it fail to return to the original zero?

 

[LiveLife]

scope that shifts zero. Could I check it by maybe locking the gun down solid, moving the reticule maybe a dozen clicks one direction horizontally, a dozen one direction vertically, then move the exact opposite amount to see if it hits original zero?

Either the scope won’t hold adjustment or there is play on the mounting system.

As long as your action/barrel are properly bedded and don't move POI away from POA.

I have done that with my 10/22 and T/CR22 on Lead Sled Solo and turned out scopes were not moving zero.

I had similar issue in the "Real world 22LR accurizing ..." thread.

With uncertain suspicion why my POI was deviating from POA, to rule out ammunition, barrel harmonics/whip, shooter input on trigger to move muzzle, etc., I cinched my rifles down on Lead Sled Solo (Even made the rocker arm solid by pressing a big roll of blue painters tape and turning the elevation knob to press hard on the tape).

After some 50 yard testing, it turned out my scope rings/mount bolts and nuts were getting loose and I was adding input on trigger. I addressed the issue by switching to Mizugiwa one piece scope mount and bolts/nuts have not come loose along with Volquartsen triggers and better "bedding" the rear of receiver, POI deviating away from POA stopped.

I am using Bushnell Dusk & Dawn 6-18x50mm and Burris FF E1 6.5-20x50mm and now POI remains at POA from range trip to range trip.

 

[Odd Job]

I think what he is asking isn't how to fix the thing, but whether the method he describes will prove the scope is defective.

 

[Atavar]

moving off zero and back will prove nothing.
Virtually every time I have had a scope not hold zero it was because of the mounts, not the scope. Double check the mounts for tightness. Grab each end of the scope and push them up down left right watching closely for even the tiniest movement.
If your mounts won’t stand up to wiggling or bumping the scope then you need new mounts. I’ll even tap the scope with a light soft mallet to check some times. You shouldn’t be able to move it.
If your scope or mounts can’t hold up to tapping or bumping they shouldn’t be on a rifle.
Remount the scope. Use a torque measuring driver and loctite.

 

[taliv]

moving off zero and back will prove nothing.

that's my experience.

however, for me it was the scopes not the mounts. the symptom was about a .2 tenth shift mostly horizontally. it would hold most of the day so once i rezeroed it at the range i'd be good for a while, but then putting it in its case or jostling it (barricades etc) would randomly cause a shift. extremely frustrating. but it's not related to dialing the turrets back and forth so doing so won't cause the issue. in my case (extremely expensive top of line scopes) it was due to the lens shifting in the housing.

 

[HowieG]

If your scope is from anybody with a decent warranty, just yank it off and send it in. I send Bushnells and Leupolds to the shop in a New York second if I even suspect the scope has a problem. They will check them for you and if they are gonzo, they will fix or replace. Peace of mind. You will know then the scope is not the issue.

 

[LiveLife]

I think what he is asking isn't how to fix the thing, but whether the method he describes will prove the scope is defective.

Virtually every time I have had a scope not hold zero it was because of the mounts, not the scope.

That's how I found out it was loose ring/mount bolts and nuts that were moving POI away from POA.

And I am not talking about flyers, but entire shot groups moving.

 

[taliv]

If your scope is from anybody with a decent warranty, just yank it off and send it in. I send Bushnells and Leupolds to the shop in a New York second if I even suspect the scope has a problem. They will check them for you and if they are gonzo, they will fix or replace. Peace of mind. You will know then the scope is not the issue.

when I sent my Schmidt und Bender back, they said there wasn't anything wrong with it. This was around the beginning of the Shift & Bender decade where pretty much everyone in PRS stopped using them because of the zero shift issues. They seem to be better now.

 

[jmr40]

Try another scope. Preferably one that has proven to work.

 

[HowieG]

when I sent my Schmidt und Bender back, they said there wasn't anything wrong with it. This was around the beginning of the Shift & Bender decade where pretty much everyone in PRS stopped using them because of the zero shift issues. They seem to be better now.

German engineering. What can I say?

 

[taliv]

German engineering. What can I say?

engineering was stellar at the time. mfg not so much. the first one i bought was perfect and i beat the crap out of it for years in matches without ever needing to adjust zero. then i got 2 more and they both had issues. years later i bought another and it's been fine. so really just seems like a temporary mfg problem (albeit one they refused to acknowledge much less address. some warranties are better than others)

 

[JFrank]

Sounds like another well known top of the line scope that has a reputation for shifting point of impact under recoil, they never admit a problem but they do fix them.

 

[Odd Job]

So, hypothetically, because I am interested in this problem also: let's say you remove the scope from the rifle and mounts entirely. Then you secure the scope in an immobile clamp, and note where POA is.
Under those circumstances, if you move the reticle a set number of clicks in several directions and then move it back the same number of clicks, and you see that it isn't at the same POA can you definitely say the scope is faulty?

 

[redneck2]

if you move the reticle a set number of clicks in several directions and then move it back the same number of clicks, and you see that it isn't at the same POA can you definitely say the scope is faulty?

One thing I didn’t think about until after I asked the question.....

I used to frequent a certain LGS. I was watching him mount a cheaper scope. After mounting it, he was doing the mechanical sight in. He would turn the windage and/or elevation screws, then rap the side of the scope with the screwdriver handle, then look through the scope to see how close to zero it was.

Asked him why he tapped the scope. He said that particularly on cheap scopes the reticule would hang up and not move until the gun was fired The recoil would jar it enough to let it settle in. This is the reason guys keep chasing zero. They over compensate because the reticule gets hung up.

 

[earlthegoat2]

My answer is this:

In my world:

No I don’t think the scope is faulty JUST because it does not repeatable move from one adjustment to another and precisely back to them. Like I said, in my world. I desire hunting accuracy and not much else. As long as that scope KEEPS the final setting, it is fine with me.

However:

I think that for a scope to be what it is supposed to be, you should have precise and repeatable adjustments along its entire adjustment range and back again.

I don’t think this is possible from an absolute standpoint but very high quality scopes will be so close as to be indiscernible and as such will be from a practical standpoint, pretty darn perfect.

 

[JFrank]

One thing I didn’t think about until after I asked the question.....

I used to frequent a certain LGS. I was watching him mount a cheaper scope. After mounting it, he was doing the mechanical sight in. He would turn the windage and/or elevation screws, then rap the side of the scope with the screwdriver handle, then look through the scope to see how close to zero it was.

Asked him why he tapped the scope. He said that particularly on cheap scopes the reticule would hang up and not move until the gun was fired The recoil would jar it enough to let it settle in. This is the reason guys keep chasing zero. They over compensate because the reticule gets hung up.

If you have to tap on a scopes turrets to get it to move or settle down you have a scope that needs replacing

 

[earlthegoat2]

If you have to tap on a scopes turrets to get it to move or settle down you have a scope that needs replacing

I do that on all my scopes. Don’t know if it does anything at all.

 

[JFrank]

I do that on all my scopes. Don’t know if it does anything at all.

It’ shouldn’t

 

[redneck2]

you have to tap on a scopes turrets to get it to move or settle down you have a scope that needs replacing

These were brand new out of the box.

I’ve heard that there is lube on the tracks that the reticule rides in. The lube is either too thick or dries out and gets sticky. The reticule adjustment mechanism attaches via springs. Shocking the scope body allows the spring to pull the reticle into place

At some point in the dark, murky past somewhere someone had suggested “exercising” both new scopes and existing ones by gently running the adjustments to the maximum travel in al, directions.

 

[JFrank]

That make sense , I’ve often extended my scopes windage and elevation, but how much lube inside a scope is something I can’t answer.

Something’s we do out of habit like tapping a turret but if you can influence a scope with a simple tap then imagine what a full recoil from a 7 mag will do.

 

[JFrank]

Sounds like another well known top of the line scope that has a reputation for shifting point of impact under recoil, they never admit a problem but they do fix them.

The scopes I’m referring to in this post cost $2300.00,

 

[243winxb]

check it for defects

https://www.bushnell.com/expert-advice/bu-blog-understanding-the-importance-of-scope-tracking.html

Bushnell on how to check tracking.

If bullet point of impact doesn't move when turning the adjustment, the spring may have taken a set. A bump has moved mine, when rifle fell off the bags, to the bench. Adjusted back to zero, still holding ok. Very Old Redfield 6X18.

 

[243winxb]

gently running the adjustments to the maximum travel in all, directions.

Most people should NOT do this. Gently means different things to most.

Customers break new scopes by trying it.

About 40 years ago, Weaver base line (cheap) scopes had 1 screw connecting the knob to the adjustment. A loose screw let you turn the knob all day, with no bullet point of impack change.