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Thread: JSB Exact heavy - 10.34gr compared to the normal 8.44gr

  1. #1
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    Default JSB Exact heavy - 10.34gr compared to the normal 8.44gr

    All,

    I have read a number of threads on some of the UK sites where guys claim better accuracy with the JSB heavy's (at 10.34gr) compared to the 8.44's. Others have said that the 8.44 can not be beaten in a 12fpe rifle...

    I am new to PCP's and are still playing around with my S400, so the application will be specifically for PCP's. Does anyone have a view on these pellets in a 12fpe PCP specifically. I have procured a tin of the heavy's, and will experiment this weekend, but was wondering if somebody else have a view? And what drop in speed can I expect (the S400 is running at 795fps with the 8.44's).

    I have experimeted a bit with pellets in my HW97k (mostly with lighter pellets as people has warned that I should not put the heavy stuff in a springer), but in the end the 8.44's were always the most accurate and my go-to pellet.
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  2. #2
    Sharp Shooter

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    I predict around 720 pfs
    All, my rifles are more accurate with them.
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  3. #3
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    Do you reckon i should also try a heavier pellet in my S500 FAC .177 will this make it more accurate ?
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  4. #4
    Sharp Shooter

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    I can only talk aout what it did in my rifles. Your S500 might not even like them.
    Only a test can confirm.
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  5. #5
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    Ok then i think i must give it a try as i know that my FPS is very high and though that a heavier pellet could make it more stable.
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  6. #6
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    what i found on my S410 the 8.44 grain jsb pellets are a lot less accurate than the AA Fields. jsb is not as predictable and there are a lot of fliers up to a inch from aim. that is why i dont use them for bench. i still have a few more tins at home to test but this was with 4 tins from different batches over the last year.
    have not had a tin of jsb 10.34 through my hands so i cant really comment on them at the moment. maybe my S410 just has a funny barrel playing tricks on me
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  7. #7
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    My S400 only likes the 8.44 JSB's. Heavies and Monsters are ok but groups are double the size from what I get with the 8.44's
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  8. #8
    Marksman

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    straightshooters.com has some quantitative data for .177 JSB Exact pellets running through a 12 ft/lb ~ 16 J HW97K

    I've captured the raw data
    @ Our Take - Beeman HW97 Air Rifle
    into a google sheet
    @ https://docs.google.com/spreadsheets...it?usp=sharing

    I'm not sure how they calculate the BC value they report, but I've graphed the data below - if you can't see a data point or series for the Express, its because its value is exactly the same as for the Predator, and so the Predator series overlays the Express series.

    Energy

    Velocity

    Ballistic Co-Efficient
    Last edited by saito; 02-10-17 at 16:16.
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  9. #9
    Sharp Shooter

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    This makes for interesting reading, but can anybody shed some light on the following question.
    How important is a good BC in FT? From what I have read, BC becomes important when hunting, as you want as much retained energy as possible on impact.
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  10. #10
    Protea Benchrest (Air) Team '15/'17

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    The pellet wind deflection is a function of your BC - the higher BC pellet you can get the less wind deflection your will have.
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  11. #11
    Sharp Shooter

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    I shoot 8.44 grain JSB exact with my S400 shooting at 743fps get a tight group at 40m (my best was 5 shots 10mm centre to centre- windy)
    This weekend I pushed the speed up and still managed to get a tight 15mm group at 40m shooting at just under 795fps. (also windy)
    I also found that JSB Exact and Air Arms Field shoot pretty much the same, but the POI @ 40m was 10mm lower with JSB than with the Air Arms Field 8.44

    I have not tried the heavies yet.

    Have a look at the pellet test I did at the range 3 weeks ago. Might give you some interesting things to think about regarding accuracy of an pellet.

    My conclusion is pretty much that it does not matter too much, if the wind is blowing, accuracy depends mainly on the shooters ability to use his knowledge to hit the target at 40m.

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  12. #12
    Protea FT Team '18
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    I have been using heavies for a while now.. in FT and occasional HFT and lots of PC and plinking ..

    I have found them to be successful and extremely accurate if you find the correct batch , out of my S400 MPR FT they group very well at 718 fps and slightly worse at 709 fps.

    In regards to wind, considerably less, at 50m in moderate wind I generally go edge of kill zone to slightly out and this has only failed twice in 8 tins of shooting.

    just a side note, your ranging has to be 110% in FT with heavies, these things fall out of the sky past 42m. In HFT i don't have any data to compare or elaborate on.

    They do have some more down range punch compared to the 8,44 grn .
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  13. #13
    Protea Benchrest (Air) Team '15/'17

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    Quote Originally Posted by Lejaun79 View Post
    My conclusion is pretty much that it does not matter too much, if the wind is blowing, accuracy depends mainly on the shooters ability to use his knowledge to hit the target at 40m.
    I agree 100% with you.

    But 4,5mm JSB Heavies and Monsters (BC about 0.03) deflect about 2/3 the amount of that of a JSB Exact (BC about 0.02). So if you do miss judge your wind - your error with a Heavy or Monster pellet will be +/- 1/3 less than what it would have been if you used a JSB exact. All of them will still have plenty of energy to punch through lost of sheets of paper
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  14. #14
    RIP Oom Hein 9/08/19

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    Quote Originally Posted by Juniork View Post
    I agree 100% with you.

    But 4,5mm JSB Heavies and Monsters (BC about 0.03) deflect about 2/3 the amount of that of a JSB Exact (BC about 0.02). So if you do miss judge your wind - your error with a Heavy or Monster pellet will be +/- 1/3 less than what it would have been if you used a JSB exact. All of them will still have plenty of energy to punch through lost of sheets of paper
    Agree 100%

    Hein
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  15. #15
    Sharp Shooter

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    Heavies are really popular over in the UK. So much so that they're very hard to find most of the time as guys buy them in block quantities.
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