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JBM Update: Measured BCs added to bullet library

Bryan Litz Ballistics

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On behalf of 'JBM Small Arms Ballistics' and 'Applied Ballistics, LLC' I would like to announce the addition of measured BC data to the JBM bullet library.

For those who are not familiar with the free JBM online ballistics calculators, this is an excellent resource for making accurate trajectory predictions as well as calculations involving stability, recoil, max range, etc.

When calculating trajectories, users can either enter a numeric BC value manually, or select a bullet from the drop down menu. Until recently, the drop down menu would use the BC that's advertised by the manufacturer. Advertised BCs may or may not be accurate for any number of reasons.
Now, the bullet library includes the BCs measured by Applied Ballistics, LLC,Bryan Litz) which are referenced to the G7 standard, and are accurate within +/- 1%.

Click here
to read about G7 referenced BCs.

The bullets in the JBM library that use the measured BCs are designated 'Litz', as shown in the following graphic. When you select these bullets, the program automatically loads the measured BC for that bullet. Just take care in entering all the other inputs accurately, and the program will output a very precise trajectory.

JBM_Lib.png


The numeric BC values of the bullets in the library are not visible to the user. If you want to know the numeric BC values, they're published in the book: 'Applied Ballistics For Long Range Shooting' for over 175 long range bullets of all brands, from .22 thru .338 caliber.

Here are some links to the information on the JBM site which explains the new addition in greater detail:
Ballistic Coefficients
Bullet Library

The JBM bullet library also uses the doppler radar measured data for Lapua bullets.

This marriage of accurate data with accurate software will make it easier for shooters to calculate reliable trajectories. You no longer have to get the accurate BCs from one place, then go somewhere else to use them; it's now all tied together in one place.

Take care,
-Bryan
 
Call me dumb,the wife does all the time between correcting me on other things) but I cannot find the link to the BC's on my calulations program to work - here is the site I am using http://www.mega.nu/traj.html The link to the bullets does ntowork.

Can you give me a link to the free JBM program with a link to the BC's that works?

Thanks,

George
 
George,
Try this link:
http://www.eskimo.com/~jbm/cgi-bin/jbmtraj-5.0.cgi

I've never seen the site at your address. It looks like some kind of re-host of the JBM site.

The calculator I've linked to above is the real JBM site that has the updated library.

Good luck,
-Bryan
 
FYI,

I've found two small bugs with the updated JBM program. First, it doesn't work with my version of Opera browser. It does work fine with FireFox and Internet Explorer.

Second, you may want to dump your cache before generating numbers. With Firefox, my browser was retaining check-box selections and altitude values from previous calculations. Clear your cache to eliminate those, or be very careful about noting each of the variables that show up BEFORE you hit the 'Calculate' button.
 

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