ballistic coefficient data

ballistic coefficient data

Joined: December 4th, 2009, 8:04 pm

December 24th, 2009, 8:46 pm #1

An earlier conversation got me thinking about this. I don't see pellet manufacturers listing the ballsitic coefficients for their pellets. There is lots of data out there concerning muzzle energies from various setups. With many guns capable of reaching out 100 yards, there could be huge differences in terminal energy depending on pellet design. While something like a Predator and a Silver Bear might seem comparable at the muzzle, what about at 50 yards? 100 yards? Maybe pellet choice makes more difference than you think.

Does anyone know of a database that contains BC values for common pellets?

Teryx
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Joined: May 12th, 2001, 1:29 pm

December 24th, 2009, 8:57 pm #2

...not only energy retention, (what's possibly even more important) but also real-world accuracy (e.g., resistance to wind drift). Pellet BC can vary from one type to another by a factor of 4 to 1.

This database complied by Patrick H. contains a few typos and blank spaces, but is still one of the best available: http://www.airgunexpo.com/airgundb/pellet.cfm

Meanwhile, the one and only pellet manufacturer that publishes velocity retention data (from which BC can be easily calculated) is poor old downtrodden and much-derided Gamo.

Nobody else - not even the much hyped brands.

Steve
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Joined: December 4th, 2009, 8:04 pm

December 24th, 2009, 9:12 pm #3

Or better depending on how you look at it. That's a great database. It really shows the folly of choosing a pellet based on how cool or wicked it looks. At 10 meters who cares, but at hunting distances you can lose much of your guns potential with the wrong choice of pellet. VERY interesting!

I'll admit, I'm guilty of Gamo deriding

Teryx
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Joined: December 7th, 2008, 3:50 am

December 24th, 2009, 9:49 pm #4

An earlier conversation got me thinking about this. I don't see pellet manufacturers listing the ballsitic coefficients for their pellets. There is lots of data out there concerning muzzle energies from various setups. With many guns capable of reaching out 100 yards, there could be huge differences in terminal energy depending on pellet design. While something like a Predator and a Silver Bear might seem comparable at the muzzle, what about at 50 yards? 100 yards? Maybe pellet choice makes more difference than you think.

Does anyone know of a database that contains BC values for common pellets?

Teryx
BC will vary many times between different rifles shooting the same pellets from the same tin. Even if you take 2 of the same model of rifle and grab pellets from the exact same tin and shoot them out of both of those rifles, often they will yield different BC data. So there is obviously more going on here to it, possibly due to slight differences in barrels, slight power plant differences, etc...
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Joined: November 17th, 2006, 3:51 am

December 24th, 2009, 11:31 pm #5

..it's just so easy to look it up on the chart and believe that's what you're going to get; why complicate it with reality?

Usually not all that far off, but on occasions will find that there is a whole lot more drop than the calculations indicate (and if you put a chronograph down range, may find it's a lot slower than predicted). One good indication of a pellet that's unhappy (and will give a lower than expected BC) seems to be to check vel. variations at the muzzle, then check again out at 20 or 25yards. IF you were getting 10 shot strings with 5 or 10fps variation at the muzzle, but find 20-25 fps variation at 20yards, then the pellet is adding some motions besides the predicted straight flight into the equation.

The good news is that when a rifle shoots way off the predicted BC of that pellet, the accuracy usually suxs and you'd not want to use that pellet anyway.
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Joined: April 25th, 2003, 11:44 pm

December 24th, 2009, 11:50 pm #6

...not only energy retention, (what's possibly even more important) but also real-world accuracy (e.g., resistance to wind drift). Pellet BC can vary from one type to another by a factor of 4 to 1.

This database complied by Patrick H. contains a few typos and blank spaces, but is still one of the best available: http://www.airgunexpo.com/airgundb/pellet.cfm

Meanwhile, the one and only pellet manufacturer that publishes velocity retention data (from which BC can be easily calculated) is poor old downtrodden and much-derided Gamo.

Nobody else - not even the much hyped brands.

Steve
then its value is extremely suspect to say the least:

Gamo Hunter 15.30 Pointed 0.220
Gamo Magnum 15.60 0.220
Gamo Master Point 16.20 0.220
Gamo Match 14.10 Wadcutter 0.220

Maybe the typewriter had the stutters?

Best wishes for The Season and Kind regards, Harry.
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Joined: November 17th, 2006, 3:51 am

December 24th, 2009, 11:55 pm #7

..but this seems more reasonable (and it's Gamo's data):
http://www.aceros-de-hispania.com/gamo- ... istics.htm
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Joined: December 7th, 2008, 3:50 am

December 25th, 2009, 2:24 am #8

..it's just so easy to look it up on the chart and believe that's what you're going to get; why complicate it with reality?

Usually not all that far off, but on occasions will find that there is a whole lot more drop than the calculations indicate (and if you put a chronograph down range, may find it's a lot slower than predicted). One good indication of a pellet that's unhappy (and will give a lower than expected BC) seems to be to check vel. variations at the muzzle, then check again out at 20 or 25yards. IF you were getting 10 shot strings with 5 or 10fps variation at the muzzle, but find 20-25 fps variation at 20yards, then the pellet is adding some motions besides the predicted straight flight into the equation.

The good news is that when a rifle shoots way off the predicted BC of that pellet, the accuracy usually suxs and you'd not want to use that pellet anyway.
I do the same with my rifles. Once I find its 'favorite' top 2 or 3 pellets, i'll chrony them at the muzzle, at 25 yrds and again at 50 yrds as well as shoot groups at various ranges. I'll let a combination of accuracy, BC, and smoothest shot cycle(least hold sensitivity) determine the numero uno.
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Joined: May 12th, 2001, 1:29 pm

December 25th, 2009, 3:36 am #9

..but this seems more reasonable (and it's Gamo's data):
http://www.aceros-de-hispania.com/gamo- ... istics.htm


Steve
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Joined: December 4th, 2009, 8:04 pm

December 25th, 2009, 4:01 am #10

..it's just so easy to look it up on the chart and believe that's what you're going to get; why complicate it with reality?

Usually not all that far off, but on occasions will find that there is a whole lot more drop than the calculations indicate (and if you put a chronograph down range, may find it's a lot slower than predicted). One good indication of a pellet that's unhappy (and will give a lower than expected BC) seems to be to check vel. variations at the muzzle, then check again out at 20 or 25yards. IF you were getting 10 shot strings with 5 or 10fps variation at the muzzle, but find 20-25 fps variation at 20yards, then the pellet is adding some motions besides the predicted straight flight into the equation.

The good news is that when a rifle shoots way off the predicted BC of that pellet, the accuracy usually suxs and you'd not want to use that pellet anyway.
That they were taking the numbers as gospel. Unless they are a pure fabrication they should serve as at least as a rough basis for comparison.
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