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Thread: Why?

  1. #1
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    Default Why?

    Maybe someone can explain.
    My HW100 .20 likes JSB Exact...a lot. I have it zeroed at 35m and the grouping is limited only by the nut behind the trigger.

    With H&N FTT and H&N Baracuda the groups look as if a shotgun was used but, at 35m, the groups also print significantly off to the left with centres about 2 to 4 cm left of the bull. I'm curious. I can understand the different weights could result in slightly different elevations and that a poor fit in the bore or bad pellet quality causes groups to scatter but can anyone explain this horizontal shift?

    The weather was totally calm with no wind and yes, I am holding the rifle up straight. Targets are taped to a cardboard box sitting on level ground so it is easy to align crosshairs vertically and horizontally.
    Last edited by JXV; 22-05-17 at 09:13.
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  2. #2
    Sharp Shooter

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    I don't really know , but here is my theory.

    Pellets of different weight and manufacture probably have a different centre of gravity causing them to be stabilized in different ways in different barrels.

    I do not believe that barrels can be manufactured in order to be exactly similar across a range or batch.

    But I could be completely wrong and off course here.



    Cheers.
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  3. #3
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    I have also noticed this trend with the S400, haven't tried many different pellets in the R10 yet, so I cant comment there. But for some reason the H&N's group low and right in the S400.
    Once zeroed though the groups are similar to the JSB's and AA's, just not quite as tight though. I've written the horizontal movement of groups from different pellets off to basically what my barrel likes or doesn't like.

    The H&N's may have different Gyroscopic characteristics, causing the groups to shift either left, or in your case from your barrel, right.
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  4. #4
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    I worked out .... 1 in 12 inch rifling twist, mv of around 860 fps translates to a pellet rotational speed of about 60 000 rpm which seems helluva quick. Any imbalance on that pellet is gonna make it fly all over....but why mostly to one side

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  5. #5
    Sharp Shooter

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    Try measuring the H&N versus the JSB Exact. Maybe that's where the difference in performance comes in.
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  6. #6
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    I find this difficult to understand. According to me if there is any horizontal or vertical force acting on the pallet you will never be able to zero the scope. Because it will only continue on the path and get wider.

    Why then is possible to zero a scope with different types of pellets at different distances ?
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  7. #7
    Sharp Shooter

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    As long as the scope is vertically in line above the barrel, as long as you hold the rifle upright then there should only be vertical rise and fall of the pellet with distance (due to gravity) and any horizontal deflection should only be due to wind .....or so the theory goes. But the H&N pellets ALWAYS shoot to the left in my rifle. Barrel harmonics?
    Last edited by JXV; 23-05-17 at 13:48.
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  8. #8
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    Quote Originally Posted by jonratter View Post
    Try measuring the H&N versus the JSB Exact. Maybe that's where the difference in performance comes in.
    Yes I get the impression the Baracudas are smaller. They are a loose fit in the magazine compared to JSB. The FTT is another issue.... lightest pellets but they chrony the slowest.....so they might be a bit tight in the barrel.

    The standard .20 barrel in the FAC HW100 rifles like mine is 600mm long and likely to be choked. Could the choke cause this issue?

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  9. #9
    Sharp Shooter

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    I will just except it, because I can't wrap my head around it.
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  10. #10
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  11. #11
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    Great link...Thanks. Explains a lot.

    My rifle shoots pretty straight from 20m to 80m with JSB. Only elevation adjustments needed 1 so I think the scope alignment is Ok.

    Learned two things I need to do though...
    1. Season the barrel with a few mags worth of each particular pellet type before shooting test groups
    2. Shoot those H&Ns at various ranges to see if they are spiralling as I suspect

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  12. #12
    Sharp Shooter

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    You can see the spiral of the pellets in this video.
    Weihrauch HW100 T Accuracy Review - Teds HoldOver (F.S.B. FAC .177) - YouTube

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  13. #13
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    And here's more reading. It may sound like an anal overkill approach but there's a bit more pellet info to glue to your memory.
    Pellet preparation guide ~ Air Rifle SA Forums
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  14. #14
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    And from the late guru Mze........
    Quote Originally Posted by mze View Post
    The H&N Medium Sniper pellet seems to be available in 4.50mm only.
    I would test these pellets thoroughly before committing to their use.

    My experience has shown that most H&N pellets sizes ending in 0 are not accurate due to loose fit.

    I recall that in 2009 at NC Blud tested 4.50mm 8.49gr H&N Field Target pellets out of two tins that he had been given.
    He fired about 10 shots and then gave the two tins to me saying, "You can have them and if you also find them to be crap, throw them in the bin".

    At one time I was advising everyone never to buy H&N FTT 5mm pellets because they were 5.00mm and delivered very poor accuracy.
    Then along came the Webley ValueMax and the Hatsan 125 both in 5mm.
    Neither the JSB 5.02 nor the .20 Webley (Crosman Premier) pellets would fit these rifles.
    The breech had to be tapered to chamber these pellets but then they would shoot at low velocity due to friction caused by tight fit.
    This where the 5.00 H&N FTT pellet became needed.
    I now stock these pellets for these two rifles.
    Last edited by jonratter; 24-05-17 at 09:10.
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  15. #15
    Sharp Shooter
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    Quote Originally Posted by McJack View Post
    I will just except it, because I can't wrap my head around it.
    Agree! Just use what works best and don't lose sleep about the rest, you need to be well rested to shoot good groups...
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