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Author Topic: The influence of bad ammo on shooting distance determination  (Read 4568 times)

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Offline afss

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The influence of bad ammo on shooting distance determination
« on: March 16, 2011, 12:19:31 PM »
Hi all,

I have a case were a bad ammunition (damp with moisture or oil) was used. Muzzle velocity was down by 50-60%. Unburned gunpowder residues were showen in the weapon and inside the cartridges, indicating a not-full burnning.
The test, to determine the shooting distance, was conducted with standard ammunition.
My question is:
Did any of you had expirience with comparing bad ammo to good one and the influence (if there was one) on shooting distance?
Thank you,
Lior
Talk softly and cary a big gun!

Offline Axel Manthei

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Re: The influence of bad ammo on shooting distance determination
« Reply #1 on: March 16, 2011, 12:51:33 PM »
Lior,

they may be a world apart.
... and you do not know how far apart they are.

In my opinion a general questions as your can not been answered without seeing the evidence personally.

Axel

Offline afss

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Re: The influence of bad ammo on shooting distance determination
« Reply #2 on: March 17, 2011, 06:52:55 AM »
Hi Axel,

The NIJ site instruct to use the suspect's weapon & ammunition. The expert did not use either! She said that using the defected ammo "could produce un reliable results". There for, I am looking for a paper which describes a comparison test between standard ammo and a "bad" one.

Lior
Talk softly and cary a big gun!

Offline Justine Kreso

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Re: The influence of bad ammo on shooting distance determination
« Reply #3 on: March 17, 2011, 02:46:23 PM »
Well, I think paper after paper supports that you should be using the suspect weapon and as close to the ammo as you can get and that anything else can produce unreliable results in itself. 

Not using either?  ???  What kind of opinion was formed?
Justine Kreso
Onondaga County Center for Forensic Sciences
Syracuse, NY

Offline Jeff Foggy

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Re: The influence of bad ammo on shooting distance determination
« Reply #4 on: March 17, 2011, 03:55:18 PM »
I am with Justine on this, you should be using the suspected gun and as similar ammo as possible.  In my lab, I would shoot Lab ammo that was very similar in style, make, etc.. to establish a baseline result and then do confirmatory tests with any submitted ammunition.  If I have enough submitted ammunition to conduct all my tests, I would use it and forego the Lab ammo portion. 

I think I understand the thought behind not using the ammo because it "could produce unreliable results" may be from not knowing how each round was affected by the moisture or oil, or to what extent it was/was not affected.  But I sure would use a few in testing to check it out.  I would rather use some submitted ammuntion and say it was unreliable based on testing than just assume it was unreliable and not use any of it. imho

Offline Tori Kujala

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Re: The influence of bad ammo on shooting distance determination
« Reply #5 on: March 17, 2011, 04:14:07 PM »
Justine & Jeff, that's the way I was trained also.  Use the weapon and evidence ammo.  If there is not enough evidence ammo, use lab ammo to get close and then confirm the distance with the evidence ammo. 
I can understand the hesitancy about using the 'bad" ammo, but it should be tried and compared to "good" ammo.

TK
Tori Kujala
Senior Forensic Scientist
Firearms & Toolmark Unit
Fort Worth PD Crime Laboratory
3616 East Lancaster Avenue
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Offline afss

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Re: The influence of bad ammo on shooting distance determination
« Reply #6 on: March 19, 2011, 08:28:41 AM »
Thank you all for your replies. I also thought that the weapon in question and some of the "defected" ammo should have been tested, and then compared to "standard" ones.
Due to erosion in the barrel, the fact that some of the gunpowder did not burned and muzzle velocity was reduced from 330 m/s to 140 m/s (!), I thought it will have some effect on shooting distance determination, however, the expert, by the state, insists it would'nt change her results.
That is why I am looking for results of an experiment which tested these points.
I will keep on looking,
Lior
Talk softly and cary a big gun!

Offline Charlie DeArmond

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Re: The influence of bad ammo on shooting distance determination
« Reply #7 on: July 17, 2012, 06:30:04 PM »
Lior,

I'm not an FTE, but I will corroborate what the FTEs are telling you here. Unless the exact same ammunition and weapon are used in testing, you have no reasonable hope of determining the performance of defective or damaged ammunition. In theory, you could use a lot of sophisticated chemistry and math to make a reasoned and compelling argument as to this, but the expense of doing this would be considerable, would have to be repeated for any / all instances, and still would lack the credibility of simply firing the gun and ammunition in evidence. Even from shot to shot, defective or damaged ammunition can vary widely in actual performance. If you test the actual ammunition, you will at least know the averages and extremes of performance exhibited by the sample.

Offline winterh

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Re: The influence of bad ammo on shooting distance determination
« Reply #8 on: November 30, 2012, 09:20:21 AM »
No mention is made as to caliber or firearm type, todays ammo is very reliable and consistant. If said ammo was military surplus or imported from a foreign source, then what you see is what you get and your initial event (duplicating the results of bad ammo) can  be impossible to duplicate...HW

Offline Eric Warren

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Re: The influence of bad ammo on shooting distance determination
« Reply #9 on: November 30, 2012, 10:21:19 AM »
IMHO, the best way to reproduce (you are correct HW that it is impossible to duplicate) the results is to compare "apples to apples" and that means, regardless of the caliber or type firearm, using the actual firearm itself and the ammunition submitted with it.  I agree with Jeff and Justine and perform my examinations the same way: I test fire the actual firearm with reference ammunition to obtain a good estimate and then test fire the submitted ammunition to confirm that bracket.


I can't think of a scenario where test firing a reference gun with reference ammunition would give you a more accurate result than test firing the evidence firearm and ammunition, unless the submitted gun was unsafe to fire and you had to fire a reference gun of the same make and model.




Offline winterh

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Re: The influence of bad ammo on shooting distance determination
« Reply #10 on: November 30, 2012, 04:49:19 PM »
I once tested a lot of 7.5 French military ammo with an arabic headstamp, made in the 50's is was as unstable as any I had previously tested. One round would fire correctly and the next would hangfire, the next would fail to fire. I destroyed the batch as being unsafe. It would be nice to know the caliber and origin of this bad ammo....HW

 

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