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Old February 6, 2019, 01:48 PM   #1
Pond, James Pond
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What’s happening here?

I’ve seen enough ballistic gel videos in slo-mo to know that this is not normal.

What is the explosion after the bullets exist.

Any thoughts as to the cause?
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Old February 6, 2019, 05:40 PM   #2
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Old February 6, 2019, 05:50 PM   #3
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OK. I'll try but basically it's a 7 sec slo mo vid of a HV bullet hit what looks to be 18" of ballistic gel.

It does a straight pass-through length-wise and as the bullet tumbles out of the other end, there is a flash in the temporary cavity which is clearly a small explosion to the point that when the cavity collapses again, grey smoke is expelled from the entry point!
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Old February 7, 2019, 12:50 AM   #4
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I've seen that in a few gel videos.

When the gelatin collapses, the air inside the cavity is compressed extremely rapidly. When you very rapidly compress air in the presence of anything that is remotely flammable, the heat generated can rise to the point of causing the air/fuel mixture to burn.

Here's a good example of it:

https://www.youtube.com/watch?v=fX4ODh1g4eM
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Old February 16, 2019, 01:57 PM   #5
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Quote:
When you very rapidly compress air in the presence of anything that is remotely flammable,
Things have changed, there was a time when atmosphere was compressed moisture became visible. Some of the most interesting effects I have seen came off the end of propellers in what looked like a screw effect on humid days.

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Old February 16, 2019, 02:00 PM   #6
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And then there was one of the most interesting pictures ever taken; it took years to be appreciated in the gun world but it won a prize in the world of art.

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Old February 20, 2019, 11:29 AM   #7
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Since Clear Ballistics Gelatin has a large percentage of paraffinic oil (which is quite flammable) within its composition this sort of thing is hardly remarkable. Rapidly compress a volatile, flammable vapor and you get adiabatic compression ignition (aka: dieseling). Pretty cool to watch though...
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Old February 20, 2019, 11:57 AM   #8
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If this is caused by the diesel effect, yhen why hasn't it been seen, over the years, before in other slo- mo vids? What is the particular "fuel mixture" cause with this bullet caliber / rifle, hel composition, weather condition that would cause that? Surely, one of the bullet / powder mfgrs could find out.
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Old February 20, 2019, 01:32 PM   #9
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Originally Posted by pwc View Post
If this is caused by the diesel effect, yhen why hasn't it been seen, over the years, before in other slo- mo vids? What is the particular "fuel mixture" cause with this bullet caliber / rifle, hel composition, weather condition that would cause that? Surely, one of the bullet / powder mfgrs could find out.
It has been documented for quite some time, numerous videos exist dating back 5, 6, 7 or more years. A little google-fu turns up lots of videos like this one:

https://www.youtube.com/watch?time_c...&v=LhBBCOIjkiM

The fuel mixture is the paraffinic oil vapor that arises under the reduced vapor pressure and atmospheric O2 produced by the bullet's entry into the test medium, compression (thanks to the ideal gas law) increases pressure as the temporary cavity collapses and by extension of that law temperature increases proportionally causing auto-ignition to occur.
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Last edited by 481; February 21, 2019 at 06:24 PM.
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Old February 20, 2019, 02:55 PM   #10
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And here I thought it was the mini nuke effect of the 10mm I keep hearing about.
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