BC (ballistic coeffieient) data on the Predator pellet
Anyone know where to find the BC (ballistic coeffieient) data on the Predator pellet .220 I’ve looked all over the internet and can’t find the data.
Thanks,
Larry
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I agree, could be wrong, but everything I’ve read states the BC is the pellet not the gun.
Mr. Lama and AV8TR Jerry has explained it better than I could. It also seems that when I compare my BC calculations to others it is always slightly different even when the velocity is the same. The difference could be caused by using a different chrony or maybe a difference in the barrels like Jerry said.
That could lead back to the different chrony numbers that someone was talking about a short while back….
Correct me if I’m wrong, but the BC has nothing to do with the gun, it’s all about the pellet/bullet isn’t it? Velocity and such will obviously be different, but things like weight and BC stay the same.
I agree, could be wrong, but everything I’ve read states the BC is the pellet not the gun.
Mr. Lama and AV8TR Jerry has explained it better than I could. It also seems that when I compare my BC calculations to others it is always slightly different even when the velocity is the same. The difference could be caused by using a different chrony or maybe a difference in the barrels like Jerry said.
You are very welcome!
The BC on the box of .223s uses a model for the velocity that round shoots at out of the test barrel. If you have information on the length of the barrel the manufacturer used, you can equate that to your gun.
Some of the bullet makers have websites that discuss how they measure BC and which model they use for which rounds. There is a lot of great information out there for those interested. Unfortunately, 99% of it regards supersonic rounds.
For most shooting, powder or air, a single BC value is plenty good enough to use tables and ballistic reticles effectively. You just want to start with a good value if your going to make scope tapes or click charts.
For a powderburner, if your gun shoots at 2500 fps instead of the 2575 fps that the manufacturer was getting, it’s not a big deal unless you shoot at ranges so far out that the round has slowed to trans or sub sonic. For an airgun, if you shoot a pellet at 1050 fps and the guy that measured the BC was shooting at 800 fps, there could be a pretty good difference in BC.
is it diff for powderburning bullets
What I think jerry is saying in his weasel words 😉 is that the BC that is advertised is somewhat of an “average” for that bullet/pellet.
If the BC differs with velocity, that means it would be different not only with every gun, but slightly different from shot to shot because it’s not 100% consistant. So you use and average BC. If you wanted a more precise BC you would measure it with your own rifle, but I’d have to imagine unless you are shooting competition it wouldn’t matter, and I’m willing to bet 90% of those guys don’t get the BC for that bullet for their personal rifle, they just use a bullet that is known to have a high average BC.
Thanks for making it complicated jerry. 😆
ok then on regular bullets say for my .223 when i buy them they have the bc stated on the box?
is it diff for powderburning bullets
You would think the gun had nothing to do with the BC but you’d be semi-wrong. How’s that for weasel words? 😆
The fact is that BC is an odd made up dimensionless number that does a fairly good job in trajectory calculations but is not without inherent limitations. For one thing, BC varies with velocity and not always linearly. That’s why there are several different models used by ballistic calculators to determine trajectory and retained energy etc. Airgun projectiles are best modeled with the model that assumes sub-sonic velocities but even that model (G1 I think) assumes a constant BC in the velocity range.
The most accurate BC calculations will start with a specific muzzle velocity and that is probably where the biggest gun to gun variation comes in. I don’t know if rifleing marks have a significant affect on BC for sub-sonic pellets but if they do, than that would introduce variation as well. How stable the pellet is i.e. wobble due to crown or twist rate vs. the balance of the pellet can also affect BC.
All these variations sometimes add up to significant differences in BC for the same pellet from different guns and sometimes they don’t. Only way to know is to measure.
Correct me if I’m wrong, but the BC has nothing to do with the gun, it’s all about the pellet/bullet isn’t it? Velocity and such will obviously be different, but things like weight and BC stay the same.
I agree, could be wrong, but everything I’ve read states the BC is the pellet not the gun.
Correct me if I’m wrong, but the BC has nothing to do with the gun, it’s all about the pellet/bullet isn’t it? Velocity and such will obviously be different, but things like weight and BC stay the same.
Here you can find BC for most pellets:
http://www.photosbykev.com/wordpress/userfiles/pelletdata.htm
http://www.photosbykev.com/wordpress/2009/01/20/air-rifle-pellet-database/
.025 sounds about right for the predator. They are not the best long range pellets but for hunting they probably are. I do know 15.8g exacts have a bc of .039 and 18.1g exacts .05 in my rifle though.
If you have a chrony, it’s easy to get average velocities at two ranges and use an online calculator to get the BC for any pellet out of your gun. I’ve done this for a number of slugs out of my big bores and the information has allowed me to make some drop charts that allowed me to get on target at distance with only a shot or two for fine adjustment.
Thanks, I did just find this report, good reading and good data, let me know what you guys think.
Don’t know, but judging by the drop, It’s Good! 😀
It will vary with almost every gun and will probably be low because of the tip. I will see if I can find the results from when I tested them and post later.
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Right, you absolutely want to get the near and far readings with the same chrony or two that read the same.