Author Topic: Exploding ammunition  (Read 1970 times)

Offline BlueHound

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Exploding ammunition
« on: July 21, 2013, 11:24:46 AM »
Someone told me that they believed ammunition was just as dangerous outside of a gun as it would be if it were loaded in a gun.  I asked him why he believed that and he said that children could take that ammo and hit it with a hammer, which could make it "go off".  I did not explain how the ammo would need something to hold the brass together and a barrel to go down before it would shoot like it were coming from a gun.  But now I wonder about how much harm would come to nearby people from shrapnel and hot powder.

Has anyone seen ammo explode for any reason, other than when it was inside of a gun? 

If you struck the primer-end of a typical 40 cal round with a hammer, would it explode?  I would think that you would need something smaller than a hammer face to ignite the primer. 

Assuming that it would explode, would it create shrapnel from the brass and bullet, or would the brass just turn inside out and the bullet move with little force behind it? 

Would the hot powder burn someone who was nearby?  I would guess that it would, but they would have to be fairly close.

What do you think?  I don't want to try it to find out and I've never seen or heard of any of this happening.

Offline Steve Cover

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Re: Exploding ammunition
« Reply #1 on: July 21, 2013, 12:44:37 PM »
The only part of a smokeless powder cartridge that detonates is the primer.
The powder itself burns to produce the pressure to push the bullet down the barrel.
Smokeless powder will not ignite from impact.
The primer raises the temperature in the case high enough to ignite the powder.

How fast the powder burns is dependent on pressure and temperature.
Confined in a firearm with very little volume to fill, the gas temperature and pressure rises rapidly.
When the pressure is high enough (say in the 10,000+ range) the bullet is driven down the barrel.
The higher the pressure, the greater the bullet acceleration and final velocity at the muzzle.

However, if you light a small pile of smokeless powder sitting out in the open, it will just burn.
With no restriction to the area the gas can expand to, pressure and temperature stay relatively low, and the burn with take a couple of seconds,
Where in a firearm, where pressure and temperature are very much higher, it burns completely in a small fraction of a second.

In the case of a cartridge outside of a firearm, striking the primer to set it off will start the firing sequence just like when it is in a firearm.
The powder will start to burn raising pressure enough to push the bullet out of the case. 
(The bullet only accelerates to about 20 FPS because there is no chamber to restrain the expansion of the case, nor Barrel friction to overcome, so it just pops out of the case like a cork.
In fact due to the "Action/Reaction" law of physics, the cartridge case would be propelled in the opposite direction.)
But, once the bullet is clear of the case the powder now has an infinite volume to fill and what pressure that was developed to push the bullet clear of the case drops off radically.
This great, sudden loss of pressure also takes away the temperature the powder needs to maintain burning.

The danger in such a circumstance, would be the primer shooting itself back out of the cartridge.
But this is no bullet, primers set off this way can attain the speed of an air rifle pellet.

SAAMI has two very good short videos of the dangers involved in smokeless powder and cartridges in a fire.
These are designed to train firemen how to fight fires where there is a large amount of gun powder and ammunition. (Fire at a gun shop, etc.)
The ones I bought about 15 years ago were about $15.00 a piece.
I highly recommend them to anyone who reloads ammunition.

In the case of a black powder cartridge, things are different.
Black powder is a low explosive. And, it can be set off by a violent impact.
Even though the infinite volume to fill scenario would still be in effect, the escape of the gas would be much more violent.

I hope this answers your question


Offline BlueHound

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Re: Exploding ammunition
« Reply #2 on: July 21, 2013, 01:36:52 PM »
Thanks Steve!  That was a better explanation than I expected.  I looked up the SAAMI info you mentioned and found a PDF document and a YouTube video.  The video did not work in Chrome, but did in IE.

Facts about Sporting Ammunition Fires


Here is a YouTube video of what happened when a man hit a round with a hammer.  Read the comments.  Some are pretty funny :)

Offline TexDaddy

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Re: Exploding ammunition
« Reply #3 on: July 21, 2013, 03:29:00 PM »
I am so jealous! I never find ammo in my yard.  :'(

Offline AlanB

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Re: Exploding ammunition
« Reply #4 on: July 21, 2013, 07:03:50 PM »
Yes, it can be tragic.  I have seen the pictures of the remains of a young soldiers hand when the rock he was using as a hammer was not working well and he decided that a 50 round would work better.  Suffice it to say, there was not much left, not sure what the final results were, but from the pictures I saw, I would imagine he is now wearing a prosthetic.

While I realize a 50 is not what is common,  the potential for bad things to happen with any round is out there.