After about 100 shots the POI is shifting…

Forums PCP Airguns After about 100 shots the POI is shifting…

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    rcmark
    Participant
    Member

    Here is the Serrano: 

    New Cricket .25 bullpup.

     I shoot 36 shots between fills(filling to 210 bar shooting down to 130 bar).

    For the first 3 fills it a tack driver at 105 yards.
     
    Around the 4th fill the POI shifts randomly but usually right or left 2 to 3 inches.

    I sight it in AGAIN. 

    On the next fill the POI shifts randomly but usually right or left 2 to 3 inches AGAIN.

    I sight it in AGAIN(now it’s almost back to the original settings). 

    Now it starts all over again and again. 

    My thoughts: 

    1. Maybe it’s not ‘broken in’ yet (NOW 1200 pellets thru it).  UPDATED.

    1a. I shoot at daybreak only when the wind is down. 

    1c. I have tried cleaning the barrel(between fills) it changed thing a little but no real help. 

    2. I have tried 3 different ‘Known Good’ scopes all act the same, it’s not the scope. 

    3. Checked all the screws/bolts I could not find any loose – all tight. 

    4. Last thought – New Barrel? 

    5. Send it to a tuner. 

    Any ideas?

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    Kgb1024
    Participant
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    With action in the stock and AT at 180 bar, loosen all 4 hex bolts till loose, turn down all bolt to it bottoms out on it’s shoulders. Pull barrel off the action about 2″ and slowly insert back, a properly aligned barrel will have an even clearance entering the action with an even O-ring compression. If miss aligned the barrel will hit the lip of the action then you force the barrel in, now the barrel has more metal contact on one side and is more subject to POI change.

    Place alignment screw in place making sure it bottoms out into the shallow hole on the barrel.

    Back out the alignment screw by 3/4 turn CCW.

    Pull barrel forward and lightly tighten the hex bolt closest to the receiver first, this will give you that .5mm clearance needed.

    Remove alignment screw and apply a criss-cross tighten sequence to about 10-12 in-Lb.

    The even torqueing will minimize the horizontal shifting.

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    rcmark
    Participant
    Member

    “Kgb1024”With action in the stock and AT at 180 bar, loosen all 4 hex bolts till loose, turn down all bolt to it bottoms out on it’s shoulders. Pull barrel off the action about 2″ and slowly insert back, a properly aligned barrel will have an even clearance entering the action with an even O-ring compression. If miss aligned the barrel will hit the lip of the action then you force the barrel in, now the barrel has more metal contact on one side and is more subject to POI change.

    Place alignment screw in place making sure it bottoms out into the shallow hole on the barrel.

    Back out the alignment screw by 3/4 turn CCW.

    Pull barrel forward and lightly tighten the hex bolt closest to the receiver first, this will give you that .5mm clearance needed.

    Remove alignment screw and apply a criss-cross tighten sequence to about 10-12 in-Lb.

    The even torqueing will minimize the horizontal shifting.

    
Thanks for the info.
    Any pictures or video?

    Thanks,

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    17bullet
    Participant
    Member

    A 1 mph breeze/wind change could move the POI at 100 yards maybe an inch. So it could be possible that you are a victim of mother nature. A change of 2.5 mph could happen with out you even realizing it.

    I would try it again another day and if needed put up some little wind flags just to make sure. I hope it is just the wind playing some tricks on you.

    Also could be bedding problem/wiggle between stock and air tube? With refilling making a change.

    Sometimes I wish for a indoor range just for the fact of getting the scope dialed in perfect. Good luck and let us know how you make out!

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    rcmark
    Participant
    Member

    “Kgb1024”With action in the stock and AT at 180 bar, loosen all 4 hex bolts till loose, turn down all bolt to it bottoms out on it’s shoulders. Pull barrel off the action about 2″ and slowly insert back, a properly aligned barrel will have an even clearance entering the action with an even O-ring compression. If miss aligned the barrel will hit the lip of the action then you force the barrel in, now the barrel has more metal contact on one side and is more subject to POI change.

    Place alignment screw in place making sure it bottoms out into the shallow hole on the barrel.

    Back out the alignment screw by 3/4 turn CCW.

    Pull barrel forward and lightly tighten the hex bolt closest to the receiver first, this will give you that .5mm clearance needed.

    Remove alignment screw and apply a criss-cross tighten sequence to about 10-12 in-Lb.

    The even torqueing will minimize the horizontal shifting.

    
Did this – no help.

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    John_in_Ma
    Participant
    Member

    Have you checked the shroud/baffles for any clipping?  Look for rub marks on the inside of the baffles, shroud cap or any shavings in the end of the shroud.
    Is the lead in(breach) even?
    How does the crown look?
    If you take out the barrel again try pushing a few pellets through it and check them for inconsistent rifling/defects from the barrel itself.
    Have you run it over a chronograph to check for inconsistent velocity?

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    rcmark
    Participant
    Member

    No clipping.
    Yes.
    Good.
    Maybe at some point.
    Shot string:

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    Kgb1024
    Participant
    Member

    Is it possible it is just a super light variable wind? Sounds like you shoot and it’s hitting left, you refill and when you go back at it maybe the wind let up or change directions, is that possible? Do you have any obstacles around your shooting lane that could cause wind turbulence?
    You may contact a tuner and ask what else causes that problem.
    Have you checked the scope mount and scope ring screws to make sure they are tight. I don’t know if you have another scope to try to see if it does the same, you will at least eliminate the scope as the problem if problem still exists

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    rcmark
    Participant
    Member

    Check Item number 2. in the original post.

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    SteveS.
    Participant
    Member

    Where did you get the rifle, I have a cricket and absolutely love it, however it took me about 4 monthes of shooting it at all pressures and gone through ten types of pellets before going with a certain bar and shooting jsb’s. Earnest Rowe is the man, if you don’t want to fiddle with it. Personally that’s what I love to due as well. Fiddle with it till it breaks me or I fix it. Best Steve

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    17bullet
    Participant
    Member

    Well it seems maybe my first post was not on the mark as you have your shooting more in control then realized.

    So then my other idea is not all bull pups are built the same!

    The Cricket seems to have a scope mount that is attached to the barrel and then also touches/connects to the air tube.Not a good idea.

    While the F/X Bobcat has a scope mount that connects to the receiver and touches/connects to the shroud. And not touching the air tube. A much less problematic approach.

    I would look no farther than the scope mount on that bullpup.

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    NeilClague
    Spectator
    Spectator

    If what you say is the case wouldn’t all Crickets suffer from the same problem? I have a feeling that one of the other members may have the answer, slight wind change. I have seen how wind can change the POI even at 40 to 50 yards, so at 100 yards only a slight change in wind strength and direction could change the POI. It might just be something that simple, Neil.

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    cawleyd
    Participant
    Member

    The fact that your shots are variable left and right, and not up and down, is a strong indicator that wind is the problem. If you run your data through Chair Gun, you’ll find that even a 5 mph wind (barely noticeable) can account for several inches of lateral POI change at 100 yards.

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    17bullet
    Participant
    Member

    If what you say is the case wouldn’t all Crickets suffer from the same problem? I have a feeling that one of the other members may have the answer, slight wind change. I have seen how wind can change the POI even at 40 to 50 yards, so at 100 yards only a slight change in wind strength and direction could change the POI. It might just be something that simple, Neil.

    The op seems to display enough intelligence on shooting with his recorder keeping and other answers given.

    And also made zero comment on my first post that referred about the possible wind change, which by the way was the first reply referring to wind.

    That the only other conclusion that might be possible is alignment or stress with the air tube and scope mount. He only states this happens right after the filling process. It would only take the slightest movement. And yes this could be unique to just his rifle.

    Comparing the 2 different designs Cricket/Bobcat of scope mounts Bobcat is simply the better choice period.

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    NeilClague
    Spectator
    Spectator

    That is only a matter of opinion, I have absolutely no problems with accuracy with my Cricket and whether one method of mounting over another is superior is a matter of opinion and not a matter of fact. If the Crickets constantly had problems and you could say without a doubt that the problems were caused by the scope tower then I would agree with you, but the majority of Cricket owners remark on how accurate they are, Every gun maker out there sometimes has a problem with one of their products, as I well know being a maker myself.  But to say one method is better than another is just a personal opinion and one I would not want to put on paper, unless I had positive proof of it, Neil.

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    Bluestone
    Participant
    Member

    If you are sure it is not the wind then I’d look at POI shift due to barrel leading. Try: clean barrel choke with hard nylon brush; pellets with smaller head size; lubing; swap barrel.  

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    Cookie
    Participant
    Member

    Have you ensured that ALL screws on the mounts are tight?

    Have you tried a different scope?

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    rcmark
    Participant
    Member

    “Cookie”Have you ensured that ALL screws on the mounts are tight?

    Have you tried a different scope?

    Look at Item number 2 and 3. in the original post.


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    17bullet
    Participant
    Member

    “NeilClague”That is only a matter of opinion, I have absolutely no problems with accuracy with my Cricket and whether one method of mounting over another is superior is a matter of opinion and not a matter of fact. If the Crickets constantly had problems and you could say without a doubt that the problems were caused by the scope tower then I would agree with you, but the majority of Cricket owners remark on how accurate they are, Every gun maker out there sometimes has a problem with one of their products, as I well know being a maker myself.  But to say one method is better than another is just a personal opinion and one I would not want to put on paper, unless I had positive proof of it, Neil.

    
Neil, Neil, Neil, Let’s not get so melodramatic please. I am not saying anything about your rifle being wrong. Or about its accuracy. But please understand some people think accuracy is just shooting a tight group in one setting. While others feel accuracy is hanging a target today and firing one shot. And then repeating that one shot on the same target for 5 different weeks. That is more POI accuracy.

    In the ops original post he states he can fire 3 fills (over 100 shots) and it is a tack driver. While my original reply to his post stated wind conditions and possibly being a victim of that, it is hard to believe that he could fire over 100 shots without experiencing a wind problem if there was one to begin with.Rcmark states only after the 4th fill does the problem of POI starts to exist. And then on the next fill the POI shifts randomly again.

    Rcmark also states shooting when wind is down, Cleaned barrel but not really any better, Tried 3 different scopes and is satisfied it is not a scope problem. And checked all screws and bolts. And it appears he has had this problem on going as he states again and again. 

    What rcmark does not state is can he go out again and get tack driver accuracy again for the first few fills. Or if now it just changes POI randomly all the time? And at fills or in-between fills? 

    Yes I had a personal opinion about the scope mount as mentioned in my reply. After being a Journeyman Tool Maker most of my life yes I am required to not only to have and make opinions but also act upon them and come up with an improvement/fix and or product. The proof has always been what was presented to my boss at the end of the day.

    And that is why I can have an opinion on Cricket/Bobcat scope mounts. It may be nothing more than which is better Chevy or Ford. 

    I will readily admit that in trying to give a suggestion to someone it can be very difficult without all the facts. But at least I tried and the op can take it or leave it. What have you to suggest other then you agreed with my reply on the wind and disagreed about the scope mount?

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    NeilClague
    Spectator
    Spectator

    melodramatic, where do you get that from? You state something that is your opinion and act like it is a fact. We all have opinions, so please lets keep them as opinions and not state them as anything else. Facts are totally different to what one person feels is correct, facts are supported by data, not feelings, Neil.

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