Scope setup difficulties
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GTA
»
All Springer/NP/PCP Air Gun Discussion General
»
Air Gun Gate
»
Optics, Range estimation & related subjects
(Moderators:
Tpatner412
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only1harry
,
GTA-Airgunner
) »
Scope setup difficulties
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Topic: Scope setup difficulties (Read 1282 times))
topknot
Shooter
Posts: 8
yes
Real Name: Peter
Scope setup difficulties
«
on:
February 25, 2017, 09:06:15 AM »
Hi
I have a new BSA Ultra SE, fitted with a Hawke Vantage Max 4012x40 scope. Pellets are JSB Exact, 0.177, 4.53mm. The rifle is wonderfully consistent, even in these out-of-practice hands.
However, there seems something not right about the scope or scope mounting and I cannot figure out what is wrong.
I zero at 25m (27yards) and all that is fine. Well, as far as I can tell, we have not had a calm day for ages and I have not yet found an indoor range. Consequently, testing at greater than 25m is a bit dodgy.
So, I set the scope to 10X mag and leave it there. I zero at 25m shooting from a stable rest then move in to 10m. POI drops by about 1.5cm (say 1/2 inch) which is a little more than I would have expected. POI also shifts left by 1cm (say 3/8 inch) which is a lot more than I would have expected.
I am very sure that the scope is mounted with the vertical line of the reticle accurately pointed at the barrel. That is, there is no scope cant on the rifle. This was check visually by projecting the reticle onto a screen with a plumb line and the rifle held level on the bench. Even if it were not properly aligned, it would have to be out by a huge amount to account for the POI shift I think.
Also, I am shooting at targets with accurately aligned verticals so I am sure the rifle is not canted.
Because of the wind, it is not yet clear what happens to the POI at longer distance.
Attached is a picture of a test this morning done at 10m (I think - if I have attached it correctly)
So - the question is - what causes the POI shift? Is it the mounting of the scope on the rails or is it related to the optics when I change the parallax setting to the new range? What can I do to find out what the problem is and then fix it?
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Anglesey, England
Real Time Recon
Marksman
Posts: 325
yes
Real Name: Roger
Re: Scope setup difficulties
«
Reply #1 on:
February 25, 2017, 09:21:36 AM »
Are you sure the Scopes 'recoil stop pin' is secure ? It s on top of the receiver and looks like this >
https://www.pyramydair.com/blog/2008/01/gamo-cf-x-gas-spring-part-1/
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Moneta Virginia
USAF Vietnam combat vet.14th Special Ops. Wing.
topknot
Shooter
Posts: 8
yes
Real Name: Peter
Re: Scope setup difficulties
«
Reply #2 on:
February 25, 2017, 10:26:47 AM »
Good point, thank you.
This rifle does not have such a stop. It is effectively recoilless, being a PCP. Also, when I return to 25m range, the zero has not shifted then so I assume the scope and its reticle have not moved.
I just went out and, at 10m, fired a group then adjusted the elevation up 30 clicks. The next group was vertically above the first by the expected amount and still offset to the left by the same amount.
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Anglesey, England
K_sqrd
Sharp Shooter
Posts: 784
Re: Scope setup difficulties
«
Reply #3 on:
February 25, 2017, 11:11:04 AM »
I had two Vortex scopes where the POI shifted by over an inch when I changed the AO setting.
This occurred between the 10 yard and ~75 yard range with the most change between
10 yards and 30 yards. Others have run into the same problem and it is not unique to any one brand.
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Arizona
topknot
Shooter
Posts: 8
yes
Real Name: Peter
Re: Scope setup difficulties
«
Reply #4 on:
February 25, 2017, 11:13:22 AM »
Dang!
That would not be good. Thing is, how can I demonstrate that is the fault if I choose to return the scope?
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Anglesey, England
K_sqrd
Sharp Shooter
Posts: 784
Re: Scope setup difficulties
«
Reply #5 on:
February 25, 2017, 12:49:42 PM »
Since you are shooting at 10 meters and sighted in at 25 meters, try shooting at 10 meters but leave the
AO set to 25 and see if the change in POI occurs. Because you are sighted in at 25 meter and shooting at 10 meters,
I would expect that the POI would be a bit low to POA due to the pellet being on the rising part of the arc path that it travels.
However, there should be no left / right change in POI if everything is in alignment.
You can also try other AO settings while still shooting at 10 meters. Make note of the AO setting and the POI for that combination.
The problem you will run into is that the image will go out of focus but try to do the best you can to center the cross hairs on your target.
The best way to see if you have a problem would be to shoot at the actual distances on a calm day but the above should give you
an idea of good or bad.
Hope that makes sense.
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Arizona
topknot
Shooter
Posts: 8
yes
Real Name: Peter
Re: Scope setup difficulties
«
Reply #6 on:
February 25, 2017, 05:50:40 PM »
Thank you. Good advice.
I did that this evening and it certainly looks like the scope will be going back to the shop.
Attached is a picture of four groups shot at 10m with the magnification at 10X (to match the 25m zeroing) and the AO set to 10, 15, 20 and 25m. By the time it gets to 20m, all is in fuzzy vision with dizzying parallax. At 25m I was surprised to get a proper group at all.
Chairgun tells me that the POI should be about 1/4 inch low at that range compared to 25m. So, the AO=20m result looks good and the AO=25m result is certainly plausible. The others not so much.
I need to try this at lower magnification as well.
«
Last Edit: February 25, 2017, 06:30:09 PM by topknot
»
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Anglesey, England
K_sqrd
Sharp Shooter
Posts: 784
Re: Scope setup difficulties
«
Reply #7 on:
February 25, 2017, 08:24:51 PM »
Looks like the scope has a problem at close range. Sorry to hear it but glad you found what the problem is.
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Arizona
dan_house
Expert
Posts: 1335
Re: Scope setup difficulties
«
Reply #8 on:
March 13, 2017, 04:14:40 PM »
left/right movement of the POI as you move in or farther out is a symptom of the scope not lined up correctly over the bore and or canted
Scott Hull has a great primer on that and how to fix it elsewhere here on GTA....
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pcp_Dave
N.U.A.H Expert
Marksman
Posts: 475
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Real Name: David
Re: Scope setup difficulties
«
Reply #9 on:
March 13, 2017, 04:36:09 PM »
I hope you can send the scope back. I was thinking of buying a hawke so I hate to see this going on but I think it's just a freak thing and a replacement will be fine.....
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Tallahassee Florida
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topknot
Shooter
Posts: 8
yes
Real Name: Peter
Re: Scope setup difficulties
«
Reply #10 on:
March 13, 2017, 06:15:32 PM »
Thank you.
I have sent the scope and rifle back to the shop for testing. I had some trouble explaining to them what I thought was going on. They should be letting me know what they find in the next couple of days.
Although you can find others who have had the same trouble, it is not likely to be a common problem. The thing about searching for issues on the 'net is that you only find the few unhappy people rather than the majority without issues.
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Anglesey, England
mpbby
Expert
Posts: 1201
Real Name: Marcos
Re: Scope setup difficulties
«
Reply #11 on:
March 13, 2017, 07:23:42 PM »
Good luck with the shop and the brand new scope.
As you got close to the subject, maybe you would like to save in your favorites -
http://www.gatewaytoairguns.org/GTA/index.php?topic=72099.0;topicseen
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São Paulo/Brazil
topknot
Shooter
Posts: 8
yes
Real Name: Peter
Re: Scope setup difficulties
«
Reply #12 on:
March 13, 2017, 07:37:09 PM »
Sorry - I am probably being dense but I do not understand. Are you pointing me to the excellent thread on cant errors?
I have studied that a lot and it was what gave me the confidence to be sure that the error is with the scope rather than my setup or technique.
BTW - is there a way inside GTA to save threads to a favourites list or is that only something I can only do in my browser?
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Anglesey, England
Taso1000
GTA Senior Contributor
Posts: 3610
yes
Real Name: Taso
Re: Scope setup difficulties
«
Reply #13 on:
March 13, 2017, 11:42:55 PM »
You could use the "notify" option. It will always be available if you click on "notifications" in the "modify profile" section in the left margin.
Taso
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Orland Park, Illinois
mpbby
Expert
Posts: 1201
Real Name: Marcos
Re: Scope setup difficulties
«
Reply #14 on:
March 13, 2017, 11:44:32 PM »
I also agree that your current problem is the scope. As you mentioned about 'cant' and it seemed to me you are a new member, I simply didn't know if you knew this excellent thread.
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São Paulo/Brazil
topknot
Shooter
Posts: 8
yes
Real Name: Peter
Re: Scope setup difficulties
«
Reply #15 on:
March 14, 2017, 08:01:40 AM »
Thank you.
Logged
Anglesey, England
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GTA
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All Springer/NP/PCP Air Gun Discussion General
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,
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Scope setup difficulties