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Acceptable Fps Spread

Discussion in 'Technical' started by hughlle, Mar 6, 2019.

  1. hughlle

    hughlle Very Active

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    Still poking my impact.

    Over 30 shots, the min and max were 763 and 782, so a spread of 19fps with a standard deviation of 5.3fps

    I've also found the paperwork from airfective, and they reported a min and max of 767 to 779, so 12 fps spread with a standard deviation of 3.8.

    How much of an impact on accuracy would those differences have? And anyone know what I should poke next to try and reduce the FPS spread?
     
    Rubio likes this.
  2. gasman

    gasman don't try this at home,,,,,,

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    I’d say that’s about right, pcp?
     
  3. hughlle

    hughlle Very Active

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    fx impact.
     
  4. gasman

    gasman don't try this at home,,,,,,

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    Do a ten shot string then see
     
  5. hughlle

    hughlle Very Active

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    Broken down into 3x10 shot strings, it's as follows

    Spread 13
    SD 4.57

    Spread 20
    SD 5.89

    Spread 10
    SD 4.32
     
  6. gasman

    gasman don't try this at home,,,,,,

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    I’d say that’s ok
     
  7. jesim1

    jesim1 Keyboard Hero

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    Weigh and size your pellets, then you will know exactly how consistent your gun actually is ;):thumb:
     
    josh9465 likes this.
  8. hmangphilly

    hmangphilly Busy Member

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    How does it group chum ?
     
  9. mikey

    mikey Pro Poster

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    From my .177 unregulated bsa ultra se using unweighed pellets I got 60 shots with a fps of 17.i was happy with these figures.
     
  10. hughlle

    hughlle Very Active

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    That's next on my list, but it's bucketing down right now. Prior to the recent poke, it was odd, would result in 3 different pellet on pellet groups from the same aimpoint.
     
  11. mikeyhall1

    mikeyhall1 2018 Forum Nice Guy

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    The Impact is regulated isn’t it?
     
  12. hughlle

    hughlle Very Active

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    Yes. Why I was wondiering if 20fps might be cause for concern.
     
  13. mikeyhall1

    mikeyhall1 2018 Forum Nice Guy

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    I’d bloody say it’s a concern buddy!
     
    Blackmax, metalman and hughlle like this.
  14. hughlle

    hughlle Very Active

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    As I say, when airfective tuned the rifle, they had a 12fps spread in 177 but only 7 in 22. Although as Jesim states, it could also be down to my pellets, and i know my current batch of exacts are fishy. Think I'll go run some magnums through and see what happens.
     
  15. Tim_B

    Tim_B Big Poster

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    I usually approach things with anything under 20fps is nothing to worry about at 50 yards/poi. I think that regulated top end rifles should be single figures when tuned or up to 15fps out the box. From your strings above, if its grouping well then you have nothing to worry about.

    Weighing the pellets may give different results, as well as the way the you do the shot strings i.e. if you wait 20 seconds between shots, is it different? 1 minute between shots, is it different?

    I fell into this when I got my crown and wanted as low as number as I could get. I settles on around 10 fps and am happy with that. For my Tuned HW it is single figures. Ultimately I then went back to group sizes....if the group size is good out to 50 yards then I tend to worry less about the FPS.
     
    audi swift and hughlle like this.
  16. Tricky13

    Tricky13 Keyboard Hero

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    I have been a bit preoccupied with pellet velocity recently and after a lot of testing i have come to the conclusion that in reality it make very little perceivable difference....my R 10 was running at around 770fps and now its at 730fps and its made no difference to my aim points at all its still exactly the same even at 60 to 100+ yards.
     
    Last edited: Mar 6, 2019
    David M, Jemsbro and Tim_B like this.
  17. mikeyhall1

    mikeyhall1 2018 Forum Nice Guy

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    Clean the barrel first mate, then re-lead with around 50 or so pellets. I’d still expect better even with unsorted pellets.
     
  18. hughlle

    hughlle Very Active

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    Just tried with some magnums, and both groups were a 10fps spread.
     
    mikeyhall1 likes this.
  19. mikey

    mikey Pro Poster

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    Is shot to shot in single figure fps..if they are then I would say the overall spread of the 19 you got would be nothing to worry abou
     
  20. Readie

    Readie Proud Member

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    Well. last year I fitted a Huma Reg to my BSA R10 Mk2 FAC due to inconsistency problems.
    Below is the shot string measured with a Combro
    I'm well pleased with this bearing in mind I do not do any pellet sorting, just pick them out the tin and load, obviously if there are any squashed ones, they get binned, but I dont study the skirts of the Bisley Magnums.

    Also there will be a tolerance/accuracy of the Combro here too

    Seems to come off the regulator at 40 shots or so

    First 2 shots a little interesting .

    FPS Ft/Lb
    1 815 23.6
    2 880 27.5
    3 927 30.5
    4 928 30.6
    5 929 30.7
    6 928 30.6
    7 928 30.6
    8 926 30.5
    9 928 30.6
    10 927 30.5
    11 922 30.2
    12 926 30.5
    13 927 30.5
    14 927 30.5
    15 927 30.5
    16 929 30.7
    17 931 30.8
    18 926 30.5
    19 926 30.5
    20 928 30.6
    21 926 30.5
    22 928 30.6
    23 929 30.7
    24 926 30.5
    25 928 30.6
    26 929 30.7
    27 928 30.6
    28 929 30.7
    29 920 30.1
    30 928 30.6
    31 924 30.3
    32 927 30.5
    33 928 30.6
    34 928 30.6
    35 928 30.6
    36 926 30.5
    37 927 30.5
    38 929 30.7
    39 926 30.5
    40 922 30.2
    41 920 30.1
    42 919 30.0
    43 914 29.7
    44 914 29.7
    45 909 29.4
    46 905 29.1
    47 904 29.0
    48 900 28.8
    49 894 28.4
     
    metalman likes this.

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