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Nephrology
05-17-11, 18:27
This is more of an expository thread as I do not have any questions about a specific cartridge.

I noticed when looking at the winchester self defense ammunition ballistics chart that some bullets performed very differently at different velocities. For example, the T-series bullets seemed to diminish in penetration as they were sent at increasing velocities - while this is undoubtedly partially a function of weight (the lower velocity ranger T series are 147gr while the hotter stuff is 127gr) I was wondering how velocity affects bullet performance across different calibers, bullet designs and ballistic media.

I also noticed that the same Ranger T loading for .357 SIG - 125gr @1350FPS - exhibited underpenetration, if anything, on the bare gelatin (10.9") compared to a nearly identical 9mm +P+ T loading (12.3" , 127gr @ 1250FPS)

For those who have done extensive gel testing, what sort of relationship do you typically see for the velocities and the expansion/performance of different bullets? I ask because principally because there seems to be an interesting nonlinear correlation between performance and velocity, which flies in the face of the "foot-lb" junkies.

wrinkles
05-18-11, 09:10
While I don't have time or the book handy right now this will answer your questions.


Bullet Penetration: Modeling the Dynamics and the Incapacitation Resulting from Wound Trauma
By. Duncan MacPherson

#ISBN: 0964357704

Nephrology
05-18-11, 11:10
Great! thanks. I will see if I can't order it through the University library.

Shawn Dodson
05-18-11, 11:24
A bullet may "over expand".

If the bullet remains intact then:

its increased surface area increases penetration resistance, and
its sectional density (the bullet's weight distributed over the surface area presented to the medium being penetrated) decreases, which decreases its penetration potential

If the bullet fragments then:
it loses both mass and momentum, which decreases penetration potential, and
its sectional density may also decrease


Sectional density - heavier bullets of the same caliber possess greater sectional density because the greater mass (weight) is distributed within the same surface area.