chrony setup

Discussion in 'Reloading' started by jimbothepunk, Oct 21, 2010.

  1. jimbothepunk

    jimbothepunk Well-Known Member

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    ive got a chrony for the weekend and im just wondering how far away from the rifle i should set it up


    thanks

    lucas
     
  2. garfield

    garfield Active Member

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    for me, with muzzlebreak and the blast, 15f. it's ok
     

  3. Russ Hatch

    Russ Hatch Well-Known Member

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    No muzzlebrake but I still use 15 feet.:D
     
  4. jimbothepunk

    jimbothepunk Well-Known Member

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    cool than ks guys just got wait for the weather to clear up
     
  5. J E Custom

    J E Custom Well-Known Member

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    I like to set up in increments that equal the screen spacing so I can back up to the muzzle for
    an actual MV because even at 15 feet there is a loss of velocity.

    Example: screen spacing is 4 feet I will set the screens at 8 Feet, 12 feet or 16 feet depending
    on the size of the rifle and calculate backwards from the front screen the loss from the front
    to the back screen. If I have a drop of 10 ft/sec between the front screen and the back and I'm at 8 foot from the muzzle I just add 20 ft/sec to the velocity and I am very close to the
    actual muzzle velocity.

    I hope that makes sense the way I explained it .

    J E CUSTOM
     
  6. kiwi3006

    kiwi3006 Well-Known Member

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    If you have never used a chrono before be real careful with your setup so you don't shoot it.

    I set the chrono up with my scope on low power and aim at a target 100 yds away, that way I can see the diffuser supports and how high above the chrono I am. Then I switch to high power and shoot at the target with no concerns.

    Stu.
     
  7. Russ Hatch

    Russ Hatch Well-Known Member

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    +1 on set up. I do the same at 15 ft.
     
  8. jimbothepunk

    jimbothepunk Well-Known Member

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    yeh thats something i had thought of knowing my luck id blow it to bits first shot lol
     
  9. garfield

    garfield Active Member

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    for @J E CUSTOM

    15f or 16 f. or more

    why so important?

    ok, the blast d'ont touch my screen but....

    when I use my soft from ipod touch, I must input the distance from my gun

    so he (soft!!) can compute the real(?) speed to exit of the barrel?

    no?

    thank you
     
  10. J E Custom

    J E Custom Well-Known Member

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    Yes !

    The reason is that when figuring drops at long distances the actual muzzle velocity is important
    and the chronograph ed velocity is slower because of the distance the bullet travels before it
    enters the first screen. the reason I measure the way I do is because I dont use anything but
    simple math to obtain the true velocity, so I have to be close to the distance i described.

    So if a person doesn't have or use a pocket computer he can get true velocities this way.

    J E CUSTOM
     
  11. Bravo 4

    Bravo 4 Well-Known Member

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    Not bad advise...however this is what I was doing with my new CED M2 I got for my birthday last month and still ended up shooting it! Long story...and embarrising so I will save the details. I baught a laser bore light to set everything up and help correct the problem.
     
  12. jimbothepunk

    jimbothepunk Well-Known Member

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    j.e. is there a calculation you have to do before you get your final result i thought it was just get some numbers and average it and there ya go? im new to all of this so excuse my stupid questions

    lucas
     
  13. Varminator 911

    Varminator 911 Well-Known Member

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    JE:

    I didn't realize a chrony gave two speeds, one at front screen and one at back. Is that really true? I thought you got the speed from front to back??
     
  14. J E Custom

    J E Custom Well-Known Member

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    Lucas.
    most chronographs sum up all of the velocities and give you- Max velocity, Minimum velocity,
    Extreme Spread, Standard deviation and average velocity.

    If yours doesn't then yes you add all of the velocities and divide by the number of shots
    and you will get the average velocity and other numbers if you look at highs and lows.

    But the velocities you get will be slightly slower than the actual muzzle velocities because of
    the loss of velocity between the barrel and the chrony.

    This loss is not important at short ranges for drop charts but at long distances it can mean
    the difference in a hit or a miss.

    Varminator.

    The Oehler 35p has Three screens and it gives you the velocity of two separate sets of
    screens that compare velocities (A proof screen against the other set of screens) to verify
    the velocities and if the two velocities are to far apart it gives you an error message so you
    can delete that round and not skew/contaminate the other shots with a bad number.

    And yes it uses the first two screens for the proof channel and the first and last screen for
    the actual velocity that is why the first set of numbers on the print out are always a little
    slower than the actual velocities because of the screen spacing on the proof is 2' and the
    actual velocity screens are 4 feet (If set at 4 feet spacing).

    This is one of the reasons I really like the Oehler 35p. It checks it's self for accuracy.

    That's why I set my chrony at 4 feet intervals . my screens are set at 4 feet and I can
    get the velocity drop from 2 feet to 4 feet and add that to the estamated velocity drop
    from the muzzle for an "estamated" muzzle velocity.

    J E CUSTOM