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Can you answer the forensic ballistics questions? (Photos.)

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November 10, 2019, 10:39 AM
sigfreund
Can you answer the forensic ballistics questions? (Photos.)
The holes are in target paper and were caused by CCI Blazer Brass 124 grain 9mm Luger bullets fired from a SIG P320.


What are the small black spots around the holes? (No, they are not part of the paper; they were not there before the shots were fired.)

What caused the gray swirls that terminate in the holes?








I ask these questions of LE officers during range sessions. Most can figure out the answer to the spots question, but no one has gotten the gray swirls question correct.




“I can’t give you brains, but I can give you a diploma.”
— The Wizard of Oz
November 10, 2019, 06:33 PM
flashguy
My guess is that the gray swirls are caused by particles on the bullet flying out from centrifugal force and the rotation of the bullet (which I would say was rotating clockwise).

How close was the target? The spots could be unburned powder.

flashguy




Texan by choice, not accident of birth

When they ask me, "Paper or plastic?" I just say, "Doesn't matter to me. I am bi-sacksual."
November 10, 2019, 08:12 PM
armadill0
I have seen those lead swirls but only when shooting rifle bullets with exposed lead on the base at 3500+ fps.

I have also seen outside lubed cast lead pistol bullets put lube splatters on the target.


armadill0
November 10, 2019, 08:58 PM
229DAK
As flashguy stated, it would help to know the distance to the target.


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The afternoon knows what the morning never suspected.
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November 10, 2019, 09:05 PM
sigfreund
Okay, another bit of information.

The shots were from about 3-4 yards.




“I can’t give you brains, but I can give you a diploma.”
— The Wizard of Oz
November 10, 2019, 10:34 PM
BlackTalonJHP
AFAIK Blazer Brass used plated pullets and is the same as Federal Champion.
Looks like the gray swirl is lead, perhaps the plating is being scored by a burr in the crown or bore.
November 10, 2019, 11:11 PM
kkina
I'd agree it is lead from the bullet core, outgassing from temperature and pressure. Since you're shooting FMJ, it is either coming from a breach in the jacket, or from the unplated tail of the bullet.



ACCU-STRUT FOR MINI-14
"Pen & Sword as One"
November 11, 2019, 07:20 AM
sigfreund
Yes, the gray swirl is lead. As mentioned the Blazer Brass bullets are normally fully plated, including over the base, but I suspect a small pinhole allowed a fine stream of lead to be expelled through the plating and deposited on the target as the bullet approached. I have also seen the same phenomenon with commercially reloaded ammunition that I believe also used plated bullets.

And the black specks are unburned powder.




“I can’t give you brains, but I can give you a diploma.”
— The Wizard of Oz
November 11, 2019, 04:49 PM
kkina
Is all Blazer ammo supplied with full plating (i.e. Total Metal Jacket or TMJ), or just their Clean-fire line? I thought their regular handgun ammo is FMJ (which means the base is not plated).



ACCU-STRUT FOR MINI-14
"Pen & Sword as One"
November 11, 2019, 05:09 PM
sigfreund
I don’t know about any of the other Blazer Brass loads, but the 9mm 124 grain that was used for the above example has plating that covers the entire bullet. Not being sure, I pulled one to check. The box, however, does say “FMJ” rather than “TMJ” which I would expect for a plated bullet.




“I can’t give you brains, but I can give you a diploma.”
— The Wizard of Oz
November 13, 2019, 11:20 AM
egregore
quote:
And the black specks are unburned powder.

I shudder to think what the inside of the gun that fired them looks like.
January 19, 2020, 08:42 AM
smithnsig
I think it is where the lands of the pistol barrel are scoring through the thin plating e posing the lead. See if a Glock or HK barrel do the same.


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