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# Performance Criteria Based Caliber Design

Discussion in 'Caliber Corner' started by Burncycle, Jan 20, 2013.

1. ### Burncycle

260
12
Aug 31, 2004
If you had an arbitrary set of specifications, such as

"One inch expansion and a total of 13" Penetration through calibrated ballistics gel"

Is there a formula to calculate the ratios of diameters, masses, weights, and velocities that would work to achieve that performance, assuming the metallurgy knowledge was there to tune the HP to expand predictably and consistently?

Obviously the more the round expands the more it experiences drag (like a parachute) and the more quickly it loses velocity in tissue which can lead to less penetration... increasing overall velocity may compensate somewhat assuming the bullet doesn't over expand or tear itself apart, so maybe increased mass (and therefore momentum / inertia) would be superior in achieving the depth of penetration with that kind of expansion. The bullet would have to be designed and tuned to those tolerances and particular velocity ranges.

Basically if you were to come up with a novel cartridge design from a clean sheet (not just a wildcat unless that would meet your criteria) just as a thought exercise, how would one go about calculating it so that it's in the ballpark?

Last edited: Jan 20, 2013
2. ### RichardBSilver Member

1,746
128
Jul 29, 2007
NC
Since I don't do any math beyond simple algebra can't give you the magic formula. Many products are the result of test, evaluate test, modify product, and test again until the desired product is created.

Previously on this site a book by someone named McPherson was referenced as a scientific starting point. Since i don't do advanced math that book never made into my library but some others here can point you in it's direction. The M4 carbine site seems to have access to many folks with technical backgrounds who could assist you.

http://www.m4carbine.net/forumdisplay.php?f=91

3. ### SCmasterblasterMillennium Member

18,512
710
Sep 24, 1999
Hartford, Vermont

418
0
Jan 26, 2012
CG wisconsin
5. ### rustytxrx

Oct 17, 2012
Texas
I am sure there are those who could calculate all the relative data. Not sure it is us . We know from fluid dymanics that the drag is proportional to the density of the fluid and proportional to the square of the speed. I guess we would need the reynolds number of the projection before expansion......

Ah, better get your calculus book out

6. ### RichardBSilver Member

1,746
128
Jul 29, 2007
NC
Burncycle, I found the book. It may or may not be what you are seeking. Many other folks on this web site found it enlightening.

[ame="http://www.amazon.com/Bullet-Penetration-Modeling-Incapacitation-Resulting/dp/0964357704"]Bullet Penetration: Modeling the Dynamics & the Incapacitation Resulting from Wound Trauma: Duncan Macpherson: 9780964357709: Amazon.com: Books@@AMEPARAM@@http://ecx.images-amazon.com/images/I/51nDpcTt9NL.@@AMEPARAM@@51nDpcTt9NL[/ame]

7. ### 1canvas

3,150
111
Feb 17, 2008
The Great State of Ohio
after hunting large game for over 40 years one thing I have learned is that performance on paper and even gel often does not square with real life on flesh perfomance.

8. ### M 7

1,406
37
May 22, 2012
Here is another book

http://quantitativeammunitionselection.com/the_book

that contains the formulas (or formulae, if you like ) that would allow you to make calculations like those. I also found the presentation of the formulas to be much clearer and more usable than in Bullet Penetration where you must first find them and then put them into more usable form.

There are also lots of examples (two whole chapters worth) that will help you use the equations, too.

From the website:

There is also a couple of models near the end of the book that can be used to calculate penetration through clothing and sheet steel panels. (Very easy to use, too. )

Last edited: Jan 25, 2013
9. ### rustytxrx

Oct 17, 2012
Texas
M 7, got the book for Kindle from amazom for \$3.98. Interesting read