Pellt BC and velocity. - .177 Baracuda

[Kragman1]

Today I found out that my R9 shoots 10.65 Baracudas (I didn't weigh them) at 790 fps.
I understand that BC is a sliding scale impacted by velocity, but I'm not really more sophisticated than that.

Can anyone help me out, to understand the BC of that pellet at that starting velocity?
I'd like to drop the info into a calculator to see how it holds velocity and get a good estimate of drop & energy out to 50 yards or so.

Thanks!

[splitbeing]

Go to the H&N website, find the .177 baracuda pellet, then scroll down to the chart generator. With the info you have, the site will provide the info you're asking for.

[Kragman1]

Thank you.

I saw that Rion, and it is helpful.
But it seems to be a generic BC, and I'm not sure if the calculator modifies the BC value based on velocity or just uses .024 as a constant.
To be honest, it probably doesnt matter much for what I'm doing anyway.  Just using this as an example to learn a little more.

Thanks again!

[Jshooter71]

You can find out what your actual BC is by measuring velocity at 2 known distances and using the BC calculator here:
https://www.airgunsofarizona.com/Calcs.html
I usually use 30 meters as my zero. So I check my velocity at the bench (1 meter from the muzzle) and then move the chrony in front of my 30 meter zero target. As long as my zero is good, I’ve never shot my chronograph. 

[ballisticboy]

Today I found out that my R9 shoots 10.65 Baracudas (I didn't weigh them) at 790 fps.
I understand that BC is a sliding scale impacted by velocity, but I'm not really more sophisticated than that.

Can anyone help me out, to understand the BC of that pellet at that starting velocity?
I'd like to drop the info into a calculator to see how it holds velocity and get a good estimate of drop & energy out to 50 yards or so.

Thanks!

Be very careful using manufacturers or any other BC values measured by anyone else, particularly if they do not make it clear what reference drag law they are using and under what conditions and by what method the BC was calculated. BC should not change by very much with velocity if the appropriate reference drag law has been chosen and the atmospheric conditions have been measured at the time of testing. The myth of BC having large changes with velocity is due to the use of a constant drag coefficient being used to obtain the BC or, in the case of at least some pellet manufacturers, the use of completely inappropriate drag laws such as the G1. Any calculator which churns out a BC without telling you what it is basing the BC on is a waste of time.

The nearest reference drag laws for round head diabolos are the GA or the GA2. Neither will be an exact fit for the Baracuda pellet, but they should not be that far out either. For 790ft/sec the value given in Chairgun should be close if used with either of the two drag laws mentioned, but it will only work with the two drag laws above. You can find a lot of free calculators which use the drag laws mentioned here. https://gpc.fotosoft.co.uk/Home.html

[Kragman1]

 Thank you Miles.

I can easily imagine that the combination of starting velocity/velocity window and the changing effect of drag as velocity decreases will be different with different pellet shapes.

And I'm sure that the best combinations of pellets and velocity windows are well known to the shooters here.  I'm kinda hoping that the 10.65 Baracudas are in the "sweet spot" when started at 800... 😁

I will definitely bone up on some combinations, likely using chairgun as you suggest.

Sometimes there is nothing better than fun learning! 

[Mrblonde40]

Hard air magazine has a list of BCs on their site.  There's only one true way to tell what it's doing at 50 yards, chrono it at 50 yards.  Just protect your chrono well.