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View Full Version : Investigative Sciences Journal: Semi-Auto Case Ejection Patterns (11/2010)



ST911
11-05-13, 10:32
Interesting paper on semi-automatic ejection patterns and the effects of different variables on case distance/direction. The data herein is useful to consider both for forensic reconstruction purposes, as well as its implications in handgun function, problem identification, and diagnostics.

Document is open source, from the Force Science Institute:
http://forcescience.org/articles/ShellCasingStudy.pdf

FIRED CARTRIDGE CASE EJECTION PATTERNS FROM SEMI-AUTOMATIC FIREARMS
William J. Lewinski, Ph.D.; William B. Hudson, Ph.D.; David Karwoski; Christa J. Redmann


Abstract

During testimony, “experts” often cite that spent cartridge case ejection locations from a semi-automatic firearm indicate the location of the shooter based on the assumption that most spent cartridge cases land to the right and rear of the shooter. The authors of this study investigated whether spent cartridge case ejection locations are an accurate indicator of a shooter’s location. Eight different semi-automatic weapons most frequently used by police officers were used to collect data from eleven different shooting positions. The results highlighted the significant inconsistency of the spent cartridge case ejection locations that occurred across test positions even when several factors including firearm type, firearm position, and ammunition were accounted for. Of 7,670 bullets fired, over 25 percent of the spent cartridge casings landed somewhere other than to the right and rear of the shooter where it is commonly accepted they should land. That pattern inconsistency is significant and demonstrates that determining shooter location from the spent cartridge case alone leads to only a tentative estimate of the shooter’s location.

williejc
11-15-13, 17:58
I wonder if the experts know that the P-38 throws brass out of the left side?

G19A3
12-11-13, 04:39
The Walther P5 too, I believe.

Voodoo_Man
12-11-13, 06:17
my gen4 g19 shot brass above and at my head, fixed now, but I'm sure that'll make em think.

jmoore
12-11-13, 08:49
Does this take into account firing with the classic "homeboy" grip while grabbing your crotch with the other hand???? Just wondering:)
BTW, thanks for the link - will use the paper in my Forensic Science class!
john

landrvrnut22
12-12-13, 10:11
They apparently didn't use a Beretta 96 in the study. Mine throws brass up, behind, to the left, and to the right. Sometimes cases end up 20'+ away. To say it has positive ejection would be an understatement.

I have talked with several other about the 96 ejection, and mine is not the only one.

I would hope the authors of this study have cleared their calenders as every good defense lawyer will be booking them to testify in court.

ST911
12-12-13, 12:13
I would hope the authors of this study have cleared their calenders as every good defense lawyer will be booking them to testify in court.

They are already active, and highly sought after, SMEs on this and various UoF topics. Check out their website for some truly outstanding reading.

ra2bach
12-12-13, 13:41
They apparently didn't use a Beretta 96 in the study. Mine throws brass up, behind, to the left, and to the right. Sometimes cases end up 20'+ away. To say it has positive ejection would be an understatement.

I have talked with several other about the 96 ejection, and mine is not the only one.

I would hope the authors of this study have cleared their calenders as every good defense lawyer will be booking them to testify in court.

may want to replace that recoil spring...

JHC
12-12-13, 18:39
Awesome OP Thanks!!!

aguila327
12-12-13, 18:53
Great post. The paper was very informative.

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