Well, I don't always trust ROF from a chrono, as you noticed, it can vary. When the BB travels down the tube, it passes between an IR transmitter and receiver, breaking the IR beam, This event is used a "start clock" and counts to the next event, which is when the BB meets the second IR beam. The time count between these 2 events is what chrono uses to determine velocity as well as ROF. If the counting misses a BB, for example it fails to break the IR beam, then it can mess up the count cycle and you get differing readings. Those readings may be more accurate with one chrono or another, and I don't use the ROF measurement as a 100% foolproof measurement anyways.
That's the same reason why sometimes a chrono won't pick up single shots either, it's because the BB doesn't brealk the IR beam to be counted, or it broke 1 beam but not the other.
Age verifier Northern Alberta
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