HFT 500 Chrono strings last 2 for now

Discussion in 'Hunter (HFT) & Field Target (FT)' started by Waldo, Nov 3, 2014.

  1. Waldo

    Waldo Active Member

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    Ran these last,pressure at the end was showing 150bar, Chrono was F1 Chrony .
    1. 8.42--762--10.86 5th string
    2. 8.36--766--10.89
    3. 8.40--763--10.86
    4. 8.48--761--10.91
    5. 8.50--749--10.59
    6. 8.42--759--10.77
    7. 8.44--763--10.91
    8. 8.46--766--11.03
    9. 8.38--776--11.21
    10. 8.42--775--11.23
    11. 6th string
    12. 8.34--766--10.87
    13. 8.48--763--10.96
    14. 8.40--764--10.92
    15. 8.50--762--10.96
    16. 8.44--764--11.02
    17. 8.44--765--10.97
    18. 8.36--762--10.78
    19. 8.46--762--10.91
    20. 8.42--761--10.83
    21. 8.36--762--10.78 That was all as it started hissing down :D:D
     
  2. rich

    rich Active Member

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    Interesting data; a x-y scatter plot shows quite strong inverse correlation between pellet weight and velocity, which is of course what you might expect, but is useful in confirming how pellet weight really needs to be taken into account for every chrono reading.
     
  3. skires

    skires Well-Known Member

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    752-776 ( 24fps spread ) over those 60 shots at 190 bar with out of the tin AA 4.52.

    I use AA 4.52 in a few rifles and I always struggle to get a better spread ( even with the reg guns ) than @ 20 - 25fps.
     
    Last edited: Nov 4, 2014
  4. Artfull-Bodger

    Artfull-Bodger Member

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    Is 60 shots the maximum you will get with that spread?

    For such a large cylinder I was expecting more?
     
  5. sven

    sven Member

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    Interesting data Waldo. But I have to disagree with rich.

    Looking deeper into the data of all 60 shots shows that the "strong" correlation between weight and velocity is due to only THREE shots (no.'s 45, 49 and 50). And even then the correlation is not very strong: R squared of only 0.01. I'd say that is a very low correlation.
    (a 100 percent correlation would give an R-squared of 1.00, at 0.60 it begins to mean something)
    The correlation without those three shots (that may be called outliers) is even poorer: R squared of 0.0007.

    And that is a strange thing. Because, as Rich says, you would certainly expect a correlation between pellet weight and velocity. And it is not apparent from these figures.
    My guess is that either there is something wrong with this dataset (weighing scale or chrono being not accurate enough, or the data of weight and velocity is mixed up) OR this 0.20 grain difference in pellet weight has no effect on velocity. Maybe it is this last fact: I have seen larger variation in weight in a tin of JSB Exact pellets. Between 8.2 and 8.7 grain in a tin. The variation here was only 0.2 grain. Probalby sorted pellets were used for this test.

    The HFT 500 performs very well: a spread of 27 fps over 60 shots. And from the chart it looks like there are many more shots in a charge:
    [​IMG]
     

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    Last edited: Nov 4, 2014
  6. Yorkshiretea

    Yorkshiretea B Grade Bandit

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    Classic outliers screwing the data, I hate Mean averages. :)
     
  7. RobF

    RobF Administrator Staff Member

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    We like graphs :D
     
  8. rich

    rich Active Member

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    Funny how we see things differently Sven. Admittedly the R squared values aren't much to write home about, but if you plot each batch separately then three of them clearly show velocity falling as pellet weight increases, and one batch is far more random and gives a trend line that is almost horizontal, if anything rising rather than falling. And that is only due to one particular reading, 759 fps and 8.48 grains, and that might even be due to a small error in data transfer.

    I notice also that all of the pellet weights are given to the nearest 0.02 grain; perhaps the scales used had this as the resolution. As we are talking about a pretty small absolute range of pellet weight values, then a coarse resolution is bound to open up the precision.

    Maybe I should have used a less weighty adjective than strong; the result is certainly clear. Very crudely, pellet weight change from 8.3 to 8.4 drops the velocity by something like 2 fps.
     
  9. rich

    rich Active Member

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    Here you go, RobF, just for you. ;)

    [​IMG]
     
  10. Lee67

    Lee67 Dink ! ...****'

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    Not sure what all those graphs mean lol, but I picked up my hft500 yesterday from solware, quick zero today at club, and it was a joy to shoot..very accurate and was lovely to hold!!.. Did me proud on our hunter course too:D..couple of points to note, side lever felt a bit graunchy to start but became lovely and smooth , and the trigger which has had a £70 solware tune free:lev..was nice and crisp, not 100% sure I like the button! but there is a few options to change to, all in all I can see it been a great rifle
     
  11. poth

    poth Whafta old Gits world champion

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    Stripped and polished my trigger myself .half hour 1dremel and autosolve .think I will start charging £140 an hour dentist wages
     
  12. Waldo

    Waldo Active Member

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    I found the side lever to spot on, certainly the trigger needs sorting, mine has quite abit of side to side movement and you can feel the ridges on the sears so a bit of a polish is required :D
     
  13. Waldo

    Waldo Active Member

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    Thanks for the replies re- Chrono strings, i only had time to run 60 shots through it on the day from a 190 bar fill it was down to 150bar . I wanted to chrono past the 100 bar mark , but inclement weather curtailed the session, :) don`t want to get it wet yet :D:D. Spent a couple of hours at the range this morning, slight x wind, hitting 10mm re-settable`s out to 60 yds was bench rested though.
     
  14. Waldo

    Waldo Active Member

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    i only had time to shoot 60, pressure was down to 150bar so plenty more shots i would have thought, going to shoot a few more strings this weekend i hope !.
     
  15. Waldo

    Waldo Active Member

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    No they were out of the tin, i weighed 10 individually wrote down each individual weight, the 10 pellets were placed in a 10m match pellet case , shot no 1 noted chrono reading and so on. Then weighed another ten, so i`m pretty sure the data for each shot is as near as damn it correct. I weighed the pellets indoors and most of them several times to make sure the reading on the scales was accurate. The scales i used were Dalman Dia 50 154.32gn x0.01gn I realise scale and chrono will have +/- variations, i was interested to see how the rifle shot. Many thanks for the graphs very interesting . Gordon.
     
  16. Waldo

    Waldo Active Member

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    I`m beginning to like graphs Rich :D:cool:
     
  17. Artfull-Bodger

    Artfull-Bodger Member

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    Aaah that explains it, I am getting 60 out of an MPR so expected considerably more from that cylinder!
     
  18. Waldo

    Waldo Active Member

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    Just had a look on BARs site, says.... Shot count - Approx 90 - .177 (4.5mm ) so going off that i may get 40 or more off the remaining 40bar, if i shoot it down to 100 bar i`ll see how far it goes before dropping off the edge. Another chrono session looming :).. Gordon.
     
    Last edited: Nov 5, 2014

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