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Author Topic: BC by Labradar  (Read 116 times)

Nvreloader

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BC by Labradar
« on: January 12, 2018, 08:40:09 AM »
Guys
Here is info on BC's when checked via Lab Radar,

http://hardairmagazine.com/ballistic-coefficients/

I know Bob might be interested.  ;)

Tia,
Don


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It is time to restore the American precept, that each individual is accountable for their actions"
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Alan

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Re: BC by Labradar
« Reply #1 on: January 12, 2018, 09:22:21 AM »
The results shown are only valid for the clime at the time the measurements were taken. What is interesting about owning a Labradar, is seeing the difference in measured BC with nothing more than a humidity and temperature change. This overlooks the altitude differences we all know exists.
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Alan

I have an Omega compressor. If you're a fellow Guild member, and you pass through Roswell, NM, I'll fill your portable tank as a courtesy.

Nvreloader

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Re: BC by Labradar
« Reply #2 on: January 12, 2018, 09:36:52 AM »
Alan

+1, plus several other factors also.

Tia,
Don
  • Western NV
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"We must reject the idea that every time a law's broken, society is guilty rather than the lawbreaker.
It is time to restore the American precept, that each individual is accountable for their actions"
Ronald Reagan

"Speeds fine, but Accuracy is final"

rsterne

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Re: BC by Labradar
« Reply #3 on: January 12, 2018, 06:05:51 PM »
I would think that the BCs listed have been corrected to standard atmospheric conditions (NTP or ICAO) as that is the normal procedure.... and the only way that you can "compare BCs" between different pellets, as they state in their preamble.... Otherwise, measurements made on different days could vary a bit, even if all the testing was done at the same altitude.... I'm pretty sure the guys running the tests know that and have made the correction, but I didn't see that mentioned (could have missed it)....

The biggest variable between their published numbers and what you might experience is likely to be if you are shooting the pellet in question at a widely different velocity.... They must be using a standard drag model from somewhere, likely either G1 or GA, and it is well known that both models are a bit out of whack, particularly in the Transonic range (Mach 0.8 - 1.2) ie over 900 fps, when used for pellets.... Notice how much lower the BCs are for the .177s, which are being shot at quite a bit higher velocity (which hurts the BC because the model is a poor one).... It's a shame they don't specify what drag model they are using, and if the BCs are corrected to ICAO (or NTP) conditions.... That would have helped tremendously....

Bob

« Last Edit: January 12, 2018, 06:13:42 PM by rsterne »
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Alan

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Re: BC by Labradar
« Reply #4 on: January 13, 2018, 03:38:05 AM »
Of course you're correct Bob, but even when I recalculate the figures for STP, they're always a bit off—say .037 vs .035. While that appears small, in the pellet world, it could be a miss.

You're also correct that drag models and other pertinent data is missing in most cases. I suspect the testers assumed we'd all know what was used, but they're not alone. If you look at the published data for bullets, you have to dig really deep sometimes to find even the drag model used. Sort of reminds me of the old beer alcohol content argument when weight vs volume isn't defined!
  • Roswell, New Mexico
Alan

I have an Omega compressor. If you're a fellow Guild member, and you pass through Roswell, NM, I'll fill your portable tank as a courtesy.