# Long Range Shooters, I need your help!

Boberama

December 17, 2009, 03:01 PM

I want to know how to calculate the downrange velocity of a projectilce from the muzzle velocity and ballistic coefficient. I found a formula at www.garandshooter.com but it only works for high velocity cartridges, and I want to calculate this for both high and low velocity cartridges. When I tried that formula for a Civil War rifle firing a Minie ball it didn't work (gave me a number higher than the muzzle velocity!).

I went online and put the same values into Hornady and JMB's ballistic calculators and it worked there. So here's what I'm thinking:

1. Hornady's online calculator takes the BC and the muzzle velocity and gives me numbers out to 1000 yards.

2. There is obviously a formula used by the program to do this.

3. So I should be able to do it with a few sheets of paper and a scientific calculator.

Do any long range competition shooters here have a formula for retained velocity, out to at least 1000 yards, that works with a Minie ball with BC .135, and at a muzzle velocity of 1,350 fps?

I hate having to go online to calculate this and if an online calculator can do it, so can I.

Maybe somebody could look at the source code for one of these online calculators and find the formula?

Again, I don't want to go online to do this, or buy a ballistic program, etc.

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Robert

December 17, 2009, 04:48 PM

The fella you are looking for is Zak Smith. He is a member on here and one of the smartest long range shooters I have ever seen. Guy does math in his head that I would have to send out to NASA.

http://demigodllc.com/

That is his site.

Jim Watson

December 17, 2009, 05:22 PM

You could get one of Dr Pejsa's books with the straight scoop and do manual ballistics calculations.

http://www.pejsa.com/

You could get Hatcher's Notebook and do it the old fashioned way with Ingalls' Tables.

I don't think I want to crack somebody's copyrighted program for you.

Boberama

December 17, 2009, 05:50 PM

Pesja's books? How accurate are the calculations?

adobewalls

December 17, 2009, 06:49 PM

What you are trying to do requires some pretty tedious math.

Here is a primer for you:

http://www.amazon.com/s/ref=nb_ss_1_15?url=search-alias%3Dstripbooks&field-keywords=modern+exterior+ballistics+the+launch+and+flight+dynamics+of+symmetric+projectiles&sprefix=modern+exterior

Boberama

December 18, 2009, 12:44 PM

I contacted Smith and this is what he had to say:

Boberama: I'm looking for a way to calculate the retained velocity at a point downrange without having to resort to a ballistics program or an online calculator, only with a scientific calculator and paper. Someone on this site said that you might know how to do this.

Thanks.

Smith: No way to do it accurately "the first time" without a ballistics calculator or measuring it in real life. You can't do it because it is computed iteratively from a set of differential equations.

Once you have some data from either method, you can of course build a model of the complexity and application you want that is easier to compute. IE, you could regular curve fitting and get a result that applies to bullets with "about a 0.3 BC" and "about 2800 fps" muzzle velocity. The more you stray, the more error your approximation would have.

-z

627PCFan

December 18, 2009, 02:24 PM

"1000 yards, that works with a Minie ball with BC .135, and at a muzzle velocity of 1,350 fps? "

Is this a theortical application, or application for a real life shot? Thats a hell of a combination

Boberama

January 17, 2010, 09:31 PM

I finally found a way that is as accurate as Hornady's online ballistic calculator.

Search "G1 Table" on google, and go to scribd and search "hatcher's notebook" and right near the end of the notebook it will tell you how to use it.

By the way, the G1 is superior to the one in hatcher's notebook and the G1 agrees very closely with Federal's data.

But you need the G1 Tables for this. So no, there is no way to do it without these. But at least I don't need a computer!:D

Boberama

January 17, 2010, 10:40 PM

I have attached a complete G1 Table to this post. Included are instructions on how to use it. It works very well within reason. Don't try finding out the velocity of a slug at 2000 yards, for example. It doesn't work so well for very low drag bullets either, but it works just as well as the Hornady Ballistics Calculator for every bullet, and is usually within 1 to 5 fps of Federal Data.

The maximum velocity is 4400 fps and the lowest it goes is 121 fps.

Here is a link to the complete table, and instructions:

http://sites.google.com/site/remainingvelocity/

Cheers!

redneck2

January 18, 2010, 07:51 AM

There is an article in the newest issue of Handloader about ballistics of BP rounds. They used extremely accurate equipment with real world shooting. What they determined is that you're basically out of luck trying to figure it out without actual numbers. Theoretical and calculated numbers were way off.

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