Recently I've taken out several of my guns that I have not shot since last summer and the point of impact on every one of them has shifted by 1"-3" at 20 yards. I had each of them perfectly sighted in last summer at 20 yards. I'm shooting the same pellets, same scope, same distance off a bench. This is extremely puzzling and frustrating. Does this happen to anyone else? Can something in the scope like the spring change over time?
Can someone explain why the POI change?
- Thread starter BassMan
- Start date
What guns? On a springer it is likely a lube issue or temp sensitive guides. A good tune will fix that for the most part. On a PCP it could be other things but I dont know enough to comment.
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Are you changing magnification on SFP scopes? Did you crono last summer and compare to the last time you shot?
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On your springers, the first thing you want to do is check your stock screws and make sure they're torqued down properly. You should probably check your scope mounts too. Also clean the barrel. A lot of people say you don't need to do this on an airgun gut I've found just a couple dry patches occasionally does help.
From there I would tear the gun down, clean out all the factory lube and relube the gun properly. It does not take a lot and iverlubing causes more issues than not. If you want to go nuts, an ARH or Vortek kit and a Vortek piston seal (if available) would be smart to install at this point.
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I did check velocities and didn't find any change. I don't know what a SFP scope is, all my scopes are AO budget (under $125) scopes.
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Temperature can cause shifts big time. If you shot them in say , 85 degrees last summer and today at 45-50 degrees. That would definately shift the POI. Another possibilty is the budget scope could be failing to track properly.
Something that consistent on all rifles across the board ...any chance it's not the rifles? Did you get new glasses between now and then?
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1-3 inches is a big shift at that range. Was the POI change up, down, or sideways. As to SFP scopes changing with magnification changes, a good scope will not do that. On a rimfire, I had a Vortec Vantage AO 2-7 power scopes that I sighted in at 25 yards on 7x high power. When I switched to 2x the POI shifted .75 inches to the right, and this was repeatable. I returned that scope and got a replacement. The replacement scope would shift .60 inches down from 7x to 2x. I returned that one and went with a Leupold ERF 3-9, and had no problems at all. So, when shooting your springers, where you shooting on the same magnification as you ended the season last year? As others said, temperature can affect springers and pump ups (in my experience with vertical changes), I am not that familiar with PCPS.
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Exactly. If a scope is changing poi when the power is changed time to throw it away and get a scope that works correctly. On a SFP scope the amount of hold over for a given distance will change with different magnification. Example: If the scope is calibrated for being true at 10x and you have a 1 mil drop you would hold over 1 mil. If you change the power to 5X its going to be 1/2 a mil hold over. The poi didnt shift just the relationship of the reticle spacing to the target. FFP scopes dont do that because the reticle hash marks stay true to the size thru the whole power range.
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I'm still wearing the same glasses. The POI shifts are generally down and to the right. I didn't really pay attention to the magnification.
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Subscribing. POI shift is like nails on a chalkboard to me. To have 1 or 2 guns in a stable that changed over 1 inch at just 20 yards would annoy me so I can only imagine the sense of betrayal to find each and every one doing it.
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One thing no one has talked about is what is common to all of his guns? The shooter. We all know springers take a lot of practice to be accurate with and it has to be maintained.
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In reality I would start with scope mointing and next step would be torquing the gun during aiming. As you said the scopes are relatively inexpensive so easy to assume the rings not any better...
If the two piece scope mounts not aligning perfect enough with the scope body on the top and the rail on bottom, that will sooner or later result in reticle loose shift with any Temp shift. How did you mount the scopes? Rings to the rail first or to the scope tube first? What the temperature shift will react either way.
Pushing your cheek to the stock or torquing the trigger is again a different issue.
The next would be the gun, the deposites in the barrel/rifling.
Go with step by step troubleshooting .
If the two piece scope mounts not aligning perfect enough with the scope body on the top and the rail on bottom, that will sooner or later result in reticle loose shift with any Temp shift. How did you mount the scopes? Rings to the rail first or to the scope tube first? What the temperature shift will react either way.
Pushing your cheek to the stock or torquing the trigger is again a different issue.
The next would be the gun, the deposites in the barrel/rifling.
Go with step by step troubleshooting .
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Are you using the same pellets that you used to sight in? Same lot? Do you lube your pellets as some lubes may change over time. It can be a quandry that's for sure. good luck
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If all the guns are moving down and right it has to be something you are doing differently, have you adjusted the ocular lens on the scope or are you imparting some cant into the rifle
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If the change is consistent across all of the guns tested, then the one non-variant is the shooter. I'd start there.
Luck,
J~
Luck,
J~