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FACTORY VELOCITY

Discussion in 'Shooting Related Threads' started by jamie65, Oct 24, 2011.

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  1. jamie65

    jamie65 Member

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    Does anyone know what the distance is that factory velocity values are taken at? ( end of shotgun barrel to chronograph screens )thanks.
     
  2. BigM-Perazzi

    BigM-Perazzi Well-Known Member

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    pm Neil Winston..
     
  3. Neil Winston

    Neil Winston Well-Known Member

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    sammie, the factories in the US use a system supplied, in various models, by Oehler Industries. The setup varies a bit manufacturer to manufacturer, but generally two (electronic) screens are set up (often) three feet apart with the mid-point between them being set at three feet from the muzzle.

    However, if I get the import of your question, does that mean that a home chronograph should be set to the same three feet (and so get the same readings) and the answer is emphatically no.

    The two are different systems, measure different things, and can only be roughly compared. Three feet will be no good for most 2 3/4 DE shells since the blast/sound will get to the home chrono at about the same time as the shot and you won't know which you are measuring.

    The best chance you have for (artificially) mimicking the speeds the factories would get if they used your equipment is to get back six or seven feet from the chronograph and use a cylinder choke, or, failing that, as open a choke as you have.

    With a cylinder choke you have a chance at estimating the quality of your reloading skills in terms of shot-to-shot variation; with a full choke you don't.

    Neil
     
  4. Paladin

    Paladin Well-Known Member

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    They don't use a light triggered Chronograph.

    According to Ken Oehler's article in the October 2006 issue of Shooting Times, they use an inductive chronograph with the first coil 18 inches from the muzzle, triggering on the trailing edge of the major clump of shot.
    The Oehler Model 71 with Inductance Sensors.

    They also use the Oehler System 84 that measures the speed of the center of mass. The system also measures chamber pressure as indicated by a conformal transducer.
     
  5. jamie65

    jamie65 Member

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    thanks much for the comments. it looks like i can get a fairly good idea of what my load to load variability is but i am quite a ways away from obtaining factory FPS values due to my equiptment and technique limitations.
     
  6. wayneo

    wayneo Active Member

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    Why is using a cylinder choke better than a full choke? Is it the way the screens can read the shot?

    Wayne
     
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