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Need help with chrony testing

Discussion in 'Shooting Related Threads' started by okiefarmer, Sep 8, 2010.

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  1. okiefarmer

    okiefarmer Member

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    I don't always trust my reloading manuals and decided to purchase a chronograph.
    I got my new "Chrony F1" set up yesterday and went to the range. I took several samples of my loads and was shocked at the speeds. All were 50-75 fps faster than
    manuals say they should be. I was about to panic when I decided to test some new Nitor 27's. I tested five of them and they all tested 1310-1335 fps when right on the box, it states 1235 fps. My questions are: Is my chrony faulty, is fps rated at x amount of yards instead of five feet from muzzle, is my 34" barrel making the difference, etc? Give me your input on this, please.
     
  2. rocko

    rocko Member

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    There are several things that can effect the velocity of your reloads.
    1) Back bored barrels and long forcing cones.
    2) Weight of shot charge.
    3) Wad pressure.
    4) Hull quality.
    5) Crimp depth.

    Most shot bars throw a light shot charge. Weigh the shot charge and adjust as needed.

    Nitro's run faster than published, around 1290 so 1335 out of a big bore gun should be about right. I would suggest you get together with someone who has a chronograph and compare.
     
  3. willing

    willing Member

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    I always shoot 5 factory loads, average and determine a correction factor. then I shoot my loads and apply the correction factor. It seems to work for me.

    Bill
     
  4. AveragEd

    AveragEd Well-Known Member

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    My chronograph manufacturer told me to deduct 35fps from the readings I get when clocking shotshell loads. "Hobby" chronographs like most of us use clock the leading object, not the mass of the shot charge like the ones used in ballistics laboratories.

    Ed
     
  5. okiefarmer

    okiefarmer Member

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    Thank you very much. This is the kind of input I was looking for. I will check mine against someone elses. I am concerned about breaking rules. One of you stated that factory nitros were 1290 and up, thus making these illegal for ATA. Speaking of fps rules, if one were questioned and checked, would he be checked with powder scales and factory reloading manuals or would he be checked with a chronograph? I am not too concerned when I see that the factory loads are also running fast.
     
  6. phirel

    phirel TS Member

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    Ed gave the correct answer.

    Pat Ireland
     
  7. Gun Dog

    Gun Dog TS Member

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    That 34" barrel will make a slight difference. At Least in my chrono experience which isn't much. I can tell a difference in average speeds when going from 28" to 32". Like say 30 or 40 fps more.
     
  8. Quack Shot

    Quack Shot Active Member

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    In order to get the most realistic readings with a light screen chronograph, it is usually recommended to use the most open choke possible. If you are using a full choke, then your readings will read higher as a rule. Even with an open choke, the readings will still not be the same as you would get from the professional induction screen setups.
     
  9. BDodd

    BDodd TS Member

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    I went through all of that over the years with the Oehler 35P. I finally concluded that barrel length makes a difference, temperature makes a difference, which choke makes a difference, and the simple fact that the homeowner chronos read the first pellet across the screens, not the swarm that follows, will make a difference. And, Pat is right that Ed is right! My final conclusion with the chrono data was to always compare a factory load that I wanted to match (or be less or more than) to my reloads through my barrel, on my gun, with my chosen choke, and at similar temps and not worry too much about the readings over the chronograph. I was lucky to find my 28" Krieghoff barrel with skeet chokes was quite close to what the manufacturers said how their shells would perform......breakemall....Bob Dodd
     
  10. gdbabin

    gdbabin TS Member

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    So it sounds to me that I'll scratch a chronograph off of my list of things I "need".



    Guy B.
     
  11. halfmile

    halfmile Well-Known Member

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    Yes, BDodd is right that pat is right that Ed is right.

    You should chronograph some other shells with the velocity stated on the box.

    30-35 FPS is about right.

    HM
     
  12. himark

    himark Well-Known Member

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    Like stated I just use a factory load and check several and then use this for my correction. I also found it to be 40 FPS strong also.
     
  13. AveragEd

    AveragEd Well-Known Member

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    Guy, I wouldn't take one off your list just yet. If you do any metallic cartridge handloading, a chronograph will tell you a lot more than just how fast your bullets are leaving the muzzle.

    For example, you fire five rounds of a test load and it shoots into a lot larger group than you'd like. Without a chronograph, you naturally assume the gun doesn't like that load. But with a chronograph, you will know the shot-to-shot deviation of those five rounds. If the deviation is small - say, 30fps or less - it's safe to assume that the gun doesn't like the bullet or powder or the amount of it. But if the deviation is large - say, 100fps - your loading technique is at fault and you need to make your powder drops more consistent.

    Even with a shotgun, knowing if those soft-shooting loads really do pack less recoil or are so slow that they can't develop much recoil is important info.

    Ed
     
  14. gdbabin

    gdbabin TS Member

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    noted Ed.. i'm just starting the .45 acp .38, 357 brass thing...
     
  15. Quack Shot

    Quack Shot Active Member

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    Guy,

    I use two chronographs in tandem. That way I have a reality check if a single load does not register what I thought it should. Making a list and checking it twice........... :)
     
  16. Dr.Longshot

    Dr.Longshot Banned Banned

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    My 34.5 Grains of Longshot, w/1 1/8th oz of #6s chronoed at 1610Fps -35fps=1575
    which is what manual says they should be.

    I just won an 80yd shoot off with them tonite, and was told #6s wouldn't break that target theat far, I said you just witnessed it. I was 3rd shot in 3-man
    and it was 3 feet off the ground. Broke it hard not a piece.


    Gary Bryant
    Dr.longshot
     
  17. zzt

    zzt Well-Known Member

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    okiefarmer, in addition to what has already been said, 5' is too close to the screen. I've found that 6' is the absolute minimum, and 8' to 10' is considerably better. You don't want any muzzle blast, etc. to interfere with the reading.

    I use my chrono to check SDs. I started 6' away, because that was what I was told was best. I got very consistent results with my standard loads, (single digit SDs). However, with some of the loads I was developing (mostly faster handicap and bunker loads) I was getting really bad SDs. The loads worked perfewctly well on targets, and there did not seem to be a "real" discrepancy in speed, so I experimented. A manufacturer of a different brand on chrono I was considering buying suggested moving back to 8' or 10'. I did and the "bad" loads suddenly became much better. In reality, they were always "better". Standing too close to the first screen was the problem.
     
  18. chikeneyes

    chikeneyes TS Member

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    All of these treads are accurate. a crony is a tool and will give you great info do not over Analise this it is not rocket science a good shell will be consistent in velocity Within 25-45 ft per second and a good pattern. go with the other shooters they all have good recipes do not try to over-power your shells it will mess up your shooting. trap shooting, skeet shooting, and sporting clays does not require a mega shell. lighter will pattern better but new shell will not be perfect either. you will find more consistency in watching your hulls and reload count than anything else
     
  19. Neil Winston

    Neil Winston Well-Known Member

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    Okie, if you are still having trouble, the link above may help.

    Neil
     
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