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Author Topic: Published BCs of the various pellets  (Read 56 times)

Alan

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Published BCs of the various pellets
« on: November 10, 2017, 04:57:16 AM »
I was unaware of this "chart", http://www.chronoconnect.com/pellet-list.html, but it does bring up an interesting fact or two. H.A.M. publishes a similar chart, and a few manufacturers publish their own data. However, about half the time the values do not agree with one another. This could be due to variations in the ambient and altitude, obviously. What I'd like to see, is the methodology used to calculate them. Labradar makes it a bit easier (and less costly) for the layman, but doesn't answer how JBS or RWS gets their data?? Anyone know?


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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.

rsterne

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Re: Published BCs of the various pellets
« Reply #1 on: November 10, 2017, 08:19:53 AM »
Unless the Standard is given that the BC is calculated with, such as G1 or GA, the number is questionable.... When the BC is calculated, it SHOULD be corrected to standard atmospheric conditions, but I'm betting most don't bother.... Notice that anyone can submit data to that list, there is a submission form at the bottom....

The Standards used to calculate the BC with, using the Cd which is the important thing, doesn't accurately reflect pellet drag in the Transonic range (MACH 0.8-1.2).... This leads to differing BC values depending on the velocity.... The GA model is an improvement over the G1 model for pellets, but until we get a better standard the test velocity should be specified as well.... You can bet that some of the incorrect data in that chart is because widely differing methods, or velocities, were used to do the calculations.... For example, the .22 cal Exact Heavy is shown with a lower BC than the Exact, and anybody who has tested those two pellet, on the same day under the same conditions, can tell you that is a crock....

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Alan

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Re: Published BCs of the various pellets
« Reply #2 on: November 10, 2017, 12:24:10 PM »
Yes it is. As I alluded to, some pellet makers publish their BCs, but those I have seen don't list the velocity much less the ambient. As you say, there needs to be a standard, however, I suspect some pellets wouldn't pass muster so to speak.
  • 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.