A ballistics software that works w/o a known velocity?


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MinnMooney
March 6, 2010, 12:53 AM
Does anyone know of a software program that will calculate and print external ballistics if the exact velocity or precise B.C. isn't known?

I want to get more "real life" drop figures than what I'm getting from the Federal, Winchester & Sierra's "Infinity I6" softwares.

The bullet manufactures like to inflate their bullets' ballistic coefficient values by using the G1 value rather than it's more realistic G7 value. Those values do me little good as the real drop does not match the program's drop figure. There is a lot of talk, also, about how most chronographs really don't give accurate velocity data but I have no idea of how to prove/disprove those statements. All I know is that the velocities that I get from my Shooting Chrony Gamma Master almost always seem to be under what my reloading manuals say they should be.... & "Yes" I am using the longer barrels (26" & 28") like they test their loads with.

I want to zero @ 100 yds, then shoot at 200, 300 & 400 yards and measure my drop at each and plug those drops into a software program to find the computed B.C. and have the software fill in and extend the drops to other distances.

Do any of you have such a software program? Where can I get it?

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JimKirk
March 6, 2010, 07:01 AM
JBM Ballistics May give you that... but your asking any software to do magic. There have to be some "knowns". You may could guess at the velocity and compare that to the results given by the JBM, then change the velocity until it matches the drop you're getting. That would then be close to the "real velocity and BC"

The simple solution would be to get a "good" Chronograph and measure the velocity, correct the velocity to "muzzle velocity" then do the calculations.
Temperature, humidity, speed of sound and other components apply when getting down to the nitty gritty of ballistics.

There are many calculators in the JBM set.


Jimmy K

counterclockwise
March 6, 2010, 11:18 PM
Qukcktarget tools in the QuickLoad (TM) suite has back calculators for BC's from various data sources, like two velocities and distance, a series of drops and distances, etc. Gathering the data for the input, like atmospherics, and two velocities at distance, can be problematic.

MinnMooney
March 8, 2010, 06:56 AM
Hey, thanks for the software info. I should have remembered QuickLoad/QuickTarget from years ago when I was playing with various software. It was too expensive for what I was doing then but it will be worth the cost now.

The JBM Ballistics software looks promising, also. I'm going to call them on Monday to see if it will do what I'm asking it to do. I think it will after reading the various descriptions.

JimKirk
March 8, 2010, 07:10 AM
By working backwards in the JBM, you should be able to come close. BC changes with speed, humidity and temperature... so does velocity to a point.

By inputing the drop figures that you gather by shooting the bullets at various distances(the known), using the velocity that you found with the chrony, moving the velocity up or down(guessing) to match the drop figures and by using the BC list that is on the JBM site, you should be able to find what you need. JBM uses the G7 function derived from G1 numbers, I am fairly sure.

There is a lot of good reading on that JBM site, take time to read it....

Jimmy K

The Bushmaster
March 8, 2010, 09:18 AM
Check out www.huntingnut.com They have a ballistics program (Point Blank) that is pretty darn good...And it's FREE!!

kelbro
March 8, 2010, 09:49 AM
Measure your drops at three or more distances (100, 200, and 300 yds) and you can get a very close muzzle velocity estimation.

Usually these questions evolve from not having the resources for shooting those distances. The data 'out' of any ballistic program is only as good as the data 'in'. There is no substitute for shooting your rifle at the distances that you need to know the drops for.

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