Re: Good news, Oehler 35P
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ryanjay11</div><div class="ubbcode-body">If someone who gets one of these would do a comparison test with several different brands of chronos, it would make for some good reading. I have heard these are the best you can get, but I would like to see some actual evidence before spending 3X some of the others are going for. I'm not skeptical that they don't work better. I think the 3 screen design would have to be more accurate than a cheap 2 screen chrono. The problem is that you don't have the ability to see the benefits until you buy one. With a $2500 scope, I can usually go to a store and compare it to others and come out with a pretty good idea what the benefits are.
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Funny you mention that.
CED (manufacturer of the M2 chrono) and Oehler both publish the frequency of the clocks in their chronos, as well as their screen distances. From this you can calculate the statistical average error rate. I'd always thought the Oehler was the holy grail of chronos but this evening I've crunched the numbers, and now I'm not so sure.
The 35P uses a 4MHz clock, which means the average timing error should be 1/8 millionths of a second. Its maximum screen distance is 15 feet (but it only comes with a mounting 4' rod). For the sake of argument, multiply 4 x 15 and we get a relative potential accuracy number of 60.
The CED M2 uses a 48MHz clock, which means the average timing error should be 1/96 millionths of a second. Its only screen distance is 2 feet. Two times 48 gives a relative potential accuracy number of 96. So the circuitry of the two indicates that the CED should have 1/3rd the average error rate from the Oehler. If you only use the OE 4' rod, the Oehler will have 6x the average error rate of the CED.
This ignores the benefit of the Oehler's third screen and its "proof channel," however, I fear the advance of IC technology has overtaken the Oehler's older technology.
So I did a little <span style="font-style: italic">more</span> figuring. Figuring a 3000 fps round, the average error rate of the 4' Oehler should be about 0.55 fps. A bit more than half a foot per second. Big whoop! Too small to notice unless your read-out displays in tenths of a fps. For the CED, the average error should be .09 fps, about 1.1 inches per second for a 3000 fps bullet. The change in error will change in inverse proportion to any change in velocity.
One thing you've got to give the Oehlers credit for, you don't find many people still using 10-year-old CEDs or Shooting Chronys. And there's plenty of Oehler users still happy with their 10-year-old chronos. But in terms of pure accuracy, I think IC technology has left it behind. Then again, do you have need an average error rate of less than .55 fps, which works out to about .00018%?
But to more directly (partially) answer your question, I do have a Shooting Chrony Beta Master and a CED M2. I have both because the Shooting Chrony breaks whenever I use it on a day that ends in a "Y", so I bought the CED and kept the other for a backup. But I tested them against each other and found that the CED is more accurate by 2.25 fps in ES per each 1000 fps of projectile velocity and by about 0.75 fps in SD per each 1000 fps.
YMMV.
