481
Member
- Joined
- Feb 22, 2009
- Messages
- 2,420
Because water cannot be compressed it can never be a legitimate medium for bullet testing, nor can it be compared to gelatin tests or to predict performance in living tissue.
k,
Actually water has already been long proven to be an acceptable ballistic test medium.
The FBI uses it as a screening medium as described in, "Applied Wound Ballistics: What’s New and What’s True":
Water can be used as a tissue simulant and causes just slightly more bullet deformation than gelatin or soap; the Firearms Training Unit of the U.S. Federal Bureau of Investigation uses it as a screening mechanism to decide which bullets expand well enough to merit further scrutiny.
In Chapter 2 of Quantitative Ammunition Selection, Schwartz describes the physics (re: bulk modulus, internal speed of sound, density) that show water to be a dynamically equivalent ballistic test medium to ordnance gelatin-
From the website:
Chapter 2 addresses the principles of mechanics, fluid dynamics, and thermodynamics underlying the quantitative model and establishes the dynamic equivalence of water and calibrated ordnance gelatin as ballistic test mediums.
- and MacPherson discusses the issue at length devoting the whole of Chapter 7 of Bullet Penetration and also specifies an optional test method using water in Chapter 10.
Both models (in QAS and BP) can be, and have been, used to predict successfully and accurately the ballistic performance of bullets in ordnance gelatin using water as a test medium.
According to the QAS website, that specific model was developed using data from over 700 gelatin tests and is as accurate as one could expect-
Based upon a modified fluid dynamics equation that correlates highly (r = +0.94) to more than 700 points of manufacturer- and laboratory-test data, the quantitative model allows the use of water to generate terminal ballistic test results equivalent to those obtained in calibrated ten percent ordnance gelatin. Besides including a variable for the density of soft tissue, the quantitative model employs a material strength variable within its governing expression that allows for the computational evaluation of any type of soft tissue. Within a confidence interval of 95%, the quantitative model predicts the terminal penetration depth of projectiles in calibrated ordnance gelatin with a margin of error of one centimeter. The quantitative model accurately predicts the permanent wound cavity volume and mass, terminal penetration depth, and exit velocity of handgun projectiles as these phenomena would occur in calibrated ten percent ordnance gelatin and soft tissue.