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Originally Posted by ClapperZapper
Drew, the most common cause of detonation that I have documented is old cartridges that have had a lot of vibration during their life. Rifle cartridges that ride on the dash of a truck or in the glove box for many years, or shotgun shells that were in a case in a dog trailer for many years, the powder grinds itself down into a state that when you touch it off it detonates instead of burns.

I don't understand this. It suggests to me that because the powder is ground finer the burning properties of the powder have changed? ClapperZapper perhaps you might explain this in more detail. As I understand powders come in many, many different flake sizes. If one powder is very fine to start with then is it close to detonating rather than burning such that a little more grinding might be all that is required?


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Nitrah #673729 04/09/26 04:04 PM
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Finely ground black & smokeless powder burns faster
Very light loads of fast burning smokeless powders in large capacity cases MAY create very high pressure.
Secondary Explosive Effect may occur with very light loads of slow burning smokeless powders in large capacity cases.
Detonation of smokeless powder has NOT been demonstrated in a shotgun shell.
Interesting reading, but one could read opinions for weeks, and the ballistic science is way beyond me
http://www.trapshooters.com/threads/smokeless-powder-ddt.245629/

https://www.osti.gov/servlets/purl/1498491

https://reloadammo.com/light-loads-can-explode/

Tamid #673734 04/09/26 04:44 PM
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Originally Posted by Tamid
Originally Posted by ClapperZapper
Drew, the most common cause of detonation that I have documented is old cartridges that have had a lot of vibration during their life. Rifle cartridges that ride on the dash of a truck or in the glove box for many years, or shotgun shells that were in a case in a dog trailer for many years, the powder grinds itself down into a state that when you touch it off it detonates instead of burns.

I don't understand this. It suggests to me that because the powder is ground finer the burning properties of the powder have changed? ClapperZapper perhaps you might explain this in more detail. As I understand powders come in many, many different flake sizes. If one powder is very fine to start with then is it close to detonating rather than burning such that a little more grinding might be all that is required?

Tamid, do yourself a big favor and Google Search "what governs smokeless powder burning rate". You will quickly get a pretty good explanation about powder compositions, coatings, granule shapes and sizes, etc.

Then remember that the phenomena where a cartridge is vibrated for an extended period, such as by rolling around the dashboard of a pickup truck traveling over rough roads, and thus removing the deterrent coatings on smokeless powder or pulverizing it into dust is not very common. It can happen, but is rare. Remember that Police vehicles carry various pistol, rifle, and shotgun cartridges many more miles than the average shooter, and they aren't routinely experiencing detonations. It also typically happens in cartridges that have loose powder charges that are not compressed by a wad or bullet, so the powder is free to shift and vibrate. So much less likely to happen with compressed loads in shot shells. That said, it's probably fortunate that Deputy Barney Fife never fired the single revolver cartridge he was issued by Andy, and carried for years.

I'm not sure how that became conflated with the Darwin Award candidates who supposedly experiment with reduced loads of military surplus rifle powder in shotgun shells.


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Nitrah #673748 04/10/26 04:59 AM
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Sorry Drew but your above text does not substantiate why finely ground smokeless powder will detonate rather then burn. From my research I have not found any source to say finely ground smokeless powder will detonate. Actually it is just the opposite the sources say finely ground smokeless powder does not change the burn/explosive properties of the powder. What can happen if the vibration of the shell is enough to cause the powder the grind smaller is what you (Drew) have explained. Now there are void spots in the shell which may cause pressure variations BUT it does not change the chemical or physical properties of the powder causing it to detonate rather than burn.

Drew I have gone back to what you wrote and I am uncertain what "secondary Explosive Effect" actually means. As I understand 'Effect" it may be similar to an explosion and cause the same result but it is still not an explosion.


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Nitrah #673749 04/10/26 07:36 AM
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"From my research I have not found any source to say finely ground smokeless powder will detonate."
I haven't either, but didn't look very hard. I said "Very light loads of fast burning smokeless powders in large capacity cases MAY create very high pressure."

re: SEE. Google Dr. Lloyd Brownell Secondary Explosive Effect and you'll find pages of light reading, with no definitive answers. There are impressive images of blown up handguns and rifles however.

And shotguns, the cause of which has not been explained

[Linked Image from photos.smugmug.com]

You might google Grain Elevator Explosions too. I'm sure you've seen some in Alberta. There was a major explosion in Wichita in 98' and Atchison in 2011

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