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chronograph question

Discussion in 'Reloading' started by bdhawk, Aug 5, 2012.

  1. bdhawk


    Mar 18, 2000
    a friend was coming over to run a few rounds through my PACT chronograph.

    i thought i would set it up before he arrived. i thought, since i have it set up anyway, i would see how much difference in speed i would get between my G20sf, and my S&W nightguard 310. i, of course, was using the same load of
    700x under a 180 grain XTP.
    i started out with the 310, all five were pretty dern close. but when i shot the G20.... four of the rounds were within 20-30fps from each other. but one round was 'bout 100fps faster than the rest. the recoil did not feel different. the instructions said that at times, the smoke would beat the bullet there, causing a false reading. this does not seem possible. granted these were somewhat light loads, with four in the 1050 fps range. oh, yeah, if this makes a difference, the wind was to my back, and i was shooting 'bout 8-10 ft. from the screens.

    no big deal, just wondering if any of you guys have any insight on this.
  2. fredj338


    Dec 22, 2004
    There is no way smoke travels faster than the bullet. If too close, the blast may trip the screens, but it's almost always an error, not 100fps diff. It's not unusual for a 100fps diff in mixed brass reloads w/ thrown charges. It just depends on the powder.:dunno:

  3. ron59

    ron59 Bustin Caps

    Jan 3, 2009
    Smyrna, GA
    When I shot 8-10 feet away, I had wild swings in my readings.

    I now shoot at closer to 20 feet away, much more consistent results.

    I think it's the blast that's affecting your reading, not the smoke.