Is your SCOPE BROKEN IF the POI changes like...

[CaptZippy]

It's a Center Point 3-9x50 Adventure Class...the one with the allen screws in the adjustment knobs, on a GAMO Whisper Deluxe. I have the same scope on the Maurader and it's POI doesn't change at all.

I noticed that each time I start a new shooting session with the Gamo, the POI (point of impact) seems to change. Shooting distance, bag rest, temperature are all constant in my basement 10 yard set up. I thought it was my holding technique/position changed from day to day at first, but the POI started moving DURING my last session. I first checked to see if the scope wiggled, then checked the screws for tightness...everything OK there. Then I did the following test to see if the adjustment knobs were working right: On a new target, I put a big +.

First shot touching, but not on the center of the +.

Then I cranked 10 clicks RIGHT windage, shot again anticipating POI move to the right...and it did 1/4 inch....so far so good.

Next go back to 0, so 10 clicks LEFT, shoot again...shot went 1/4 high, but on center...so, OK I may not have been breathing right, but at least it was on center vertically.

Now 10 clicks LEFT windage, shoot. This time 1/2 to the left, on the horizontal line. I was expecting 1/4", but got twice that....Problem with the scope or the shooter...not sure, but I am seeing a difference in the correct direction, so I still think it's OK.

Return to 0 with 10 clicks RIGHT, shoot, and I'm on the + again. I feel the windage knob is working OK.

Elevation test:

10 clicks UP, shoot. POI about 5/8" high on vertical center. Great...what you'd expect. Return to 0 with 10 clicks down. Shoot again and POI only moves down about 3/8"...about 1/4 high of 0. Wast it me?...shoot again. Still about 1/4 high. Instead of monkeying around re-finding 0, I dialed in 10 clicks Down to see if another 10 clicks DOWN then 10 UP would bring it to 0.

10 clicks DOWN. POI was 1/4" below 0. Shoot again. still 1/4" below 0 (at least its consistent). So I return to 0 with 10 clicks UP. Another shot. Now POI is 1/2" ABOVE 0. Shoot again....still 1/2" high.

Conclusion: I think there is something wrong with the elevation adjustment where the number of clicks UP do not produce the same change in POI as the same number of clicks DOWN. Therefore after applying ANY UP adjustment, you have to add more DOWN while adjusting to move your POI the same distance.

I know this test doesn't specifically address the POI moving during a session or from day to day when you AREN'T making any scope changes, but I thought it might be an indicator that perhaps there is something loose inside causing the above and may also cause the POI to move under normal use?

I don't have alot of experience with scopes...looking for some guidance/advise from you seasoned professionals on what the problem might be...

Thanks

Semper Fi

Tom

[CaptZippy]

LIA...that was my suspicion and I was trying to figure a way to prove it.  If you were to suspect you had a bad scope, how would you go about validating/verifying it was bad?

[Uncle J]

I had the same problem with my whisper, have a centerpoint 4x16x40, went to wal-mart and  got another one, still had the same problem. Decided to pull a dry patch through the barrel after every ten shots, POI did not move as much, made a difference, was able to stay in a dime size target at 20 yards most of the time. I don't know if my whisper leads up more than most rifles and causes the POI to shift, or maybe I need a better scope than the centerpoint and cleaning it with a dry patch is all in my mind.  My whisper likes the jsb 8.4 grain.

[CaptZippy]

Thanks Uncle J:  I'll give it a try.  What ever it takes to get in and...stay in the black.

[Uncle J]

CaptZippy,

Here is some pictures of the weed eater string I use. I found if I put a little bend in the end I feed though first it won't hang up in the MuzzleBrake. I use one 22 cal patch, I use the tip of a roofing nail to start the hole in the patch and than thread the line though the patch. Hope this helps. Let me know.

Jeff

[LongIslandArcher]

On my friend's scope, the crosshairs kept settling on a position on the target between 6 & 9, 3" from center, no matter how many times he readjusted the scope to put the crosshairs back in the center.  Got to a point where there was no adjustment left as the knobs wouldn't turn anymore.  I had the same problem with my scope, except that I kept hitting 6 o'clock, no matter how many times I adjusted the elevation until I couldn't adjust it anymore.  I sold my SS to another friend of mine but I did tell him about the scope issue.  I only charged him half what I paid because he was tight on money and wanted to play too.  My first friend ordered the Leapers scope and will be installing it soon.  As soon as he tells me it's good to go, he'll tell the other friend (that I sold the rifle to) that that's the scope to get.  So, if the scopes at a point where you can't turn the adjustment knob anymore then the scopes are busted.  

Cleaning out the bore may help and I hope that that's the only issue with the rifle.  Good luck.  Let us know what you find.

[gamo2hammerli]

Seems like your Centerpoint is toast from your test.  When I adjust my turrets I get into a habit of rapping the turret or scope tube 8 or 10 times to let the spring inside settle.  Some others, lets say they want to turn 5 clicks....they would turn 8 clicks and then turn back 3 clicks.  Less expensive to mid-priced scopes are not that precise with their turrets.

[airiscool]

What Stanley (Gamo2h) said !!!

However, as much as I'd like to at timers ..... I don't rap on the scope - I shoot at least three shots throught before I "believe" any scope re-adjustments I've done.

Except with my Sightron. It has special elevation/windage linkages that the adjusting screws are mechanically locked to the retical so it "walks" shots, single click by single click, back and forth.

Paul

[BWANA]

Are you sure it's not parallax? I had a similar problem and I thought it was the scope's fault until I got the scope adjusted for the correct parallax for my basement range. I only have 25 feet to shoot indoors. Other problems could be hold or temperature. I store my guns in a cool spot in the house and sometimes it takes 5 or 6 shots for them to settle in and warm up when I start a new shooting session. I've found that the gun is usually more accurate than I am. I wouldn't replace the scope if you are only off by 1/4 inch. But then, I'm cheap. Good luck.

[ten4copy]

My whisper is very hold sensitive... so it's usually me. This may be a work out or maybe a hassle, but you can always pull your known working scope and put on that ag or the other way around. It's a long process, but at least you'll know if it's really the scope or not. It could also be the pellets too, maybe it just doesn't like the pellets you're shooting, hence the spread, and not the poi.  I could be wrong, but just my .02.

[RedFeather]

Do you have another gun to try the scope on? Maybe a rimfire where the double recoil is not a factor? That's the only way to test your scope. I've seen where some of the CP scopes, even the ones they are putting on the Crosman combo's, aren't holding up on the magnum springers. I bought a 4X16X42? (WalMart CP) for my 54 but I'm probably not even going to try it on that - with a Damp mount, too. If you don't have another gun for the test and still have the receipt, take the scope back for an exchange or, even better, a refund you can apply towards a more robust scope. Good luck!

[DMikeM]

My Leapers (same as Centerfire) Bug Buster 3-9x32 does the same exact thing. I was thinking that my B26 was broken because it was so bad. I found that once I got it to zero (about 100 shots) mark the turrets and when I want to shoot spin the turrets a few times then back to the mark and it will hold for about 20 shots. Then you have to spin again as they will all the sudden jump from 1 inch to 3 inches in any direction.

[Uncle J]

CaptZippy,

Don't know if this is the problem but seems to have helped with my whisper, used JB paste to clean my barrel, so far don't have to dry patch after every ten shots, time will tell. Check my before and after patches. Check the attached link for instructions on using JB Paste.

http://www.pyramydair.com/blog/2005/11/is-your-airgun-barrel-really-clean.html

[CaptZippy]

Those are some great groups Uncle J.  My goal is to get to where you are.  I cleaned the bore yesterday...it was pretty dirty.  The patches were really gray.  Eventually they came out clean.  Did some more shooting and it seems I can get the scope adjusted, then after several shots...it goes wild again.  Maybe I'm experiencing the same thing as DMikeM.  What ever it is, it's frustrating.  

I'm going to take the scope and mounts completely off today and put the original Gamo scope back on and see if it improves.  

Thanks for everyone's input...I get the feeling that many of you have gone through this before.  I appreciate you sharing your experience.

SF
Tom

[Uncle J]

CaptZippy,

Those weren't groups, those were patches I pulled though my whisper, I wanted you to see the first patch, it  clearly showed that there was something in the barrel, may be a burr or something that was collecting lead and deforming the pellets as they went by it. All I know is that it is gone now and my whisper shoots better, hope it stays that way.

Jeff