[Southpaw]

Does anyone have the formulas for calculating the ballistic coefficient of a bullet or the Thorniley Stopping Power to calculate the stopping power of a round? If you do, could you please post them for me? I need them to complete a table I'm building.

Thanks in advance.

 

[Jack Monteith]

Hi, southpaw:
  There's only two ways to calculate BC that I know of.  One is to fire a bullet over two chrongraphs a fair distance apart (50 yards plus) and do the math. The other is the Bugless-Coxe method, which you need Hatcher's notebook for. You compare the bullet shape to the table (page 571-572), determine the form factor "i" and divide the sectional density by it.  BC = Sd/i.  Hatcher's Notebook is still in print and you'll find it very useful.

  Sniff around on Brad Millard's site. IIRC, there's another method there. <a href="http://www.cybermesa.com/~jbm/index.html

Later:" target="_blank">http://www.cybermesa.com/~jbm/index.html

Later:</a>
Goto jbm, click on Ballistics, then Calculations, then Bullet Drag & Twist. It's set up for typical high power rifle bullets and won't work with Marshall's bullets because it won't accept a meplat diameter greater than half the bullet diameter. However, you can learn a lot at this site. Note that it gives a different BC for each velocity step. Only Sierra tells you that, and their manual is a good read for intermediate level ballistic theory.

   I've got about a dozen "killing power" formulas.  None are perfect, but most are useful. For a long discussion, try:
<a href="http://ulfhere.freeyellow.com/ballistics/wounding.html

Bye" target="_blank">http://ulfhere.freeyellow.com/ballistics/wounding.html

Bye</a> for now
Jack    

(Edited by Jack Monteith at 9:55 pm on May 16, 2001)

 

[Southpaw]

Jack, thanks a lot for your help.  I think BC may be something I have to live without, unless I can find a formula that can be used to calculate the 'i' value.

The ballistics discussion you pointed me to, 'Shooting Holes in Wounding Theories', I've read.  I thought it was pretty good.  I use his penetration and cavitation formulas in my table.

Though these calculations are imprecise predictions of what one can expect in reality, I think they might be fare as a comparison of effectiveness between two bullet when the only variables are caliber, weight, meplat, velocity and sectional density.  All other variables, such as barrel length and gun weight, being constant.

If you see this, I'd be interested in your opinion, as well as anyone else's.

Thanks again.

God bless