Ballistics question

[thunderball]

Perhaps some of you ballistically-gifted gents can help settle small debate. We were camping a few weeks back and while we sitting round our campfire two tipsy boar hunters came out of the woods and invited themselves to sit down at our fire. No problem thought we and we offered them some whiskey. They were surprised we all spoke Japanese and were eager to show us their guns (we were equally interested as they are a fairly rare sight in Japan). One guy (as I said they'd obviously been drinking) pulls the clip out of his rifle and is holding it directly over the fire and shakily taking rounds out to show us. Luckily none actually dropped into the fire and we oohed and aahed over the cartridges and handed them back. They finished their whiskeys and left into the darkness.

Now begins our own tipsy conversation. "Those things could have gone off if held them over the fire any longer", says one friend. "Not in a million years", says I. "Well if one had dropped into the fire I was ready to bolt", says a third friend. "They would have just gone 'poof' and wouldn't have actually gone anywhere", says a fourth. We continued on like this for some time and never really came to any agreement over the matter.

My questions are:

1) Would a cartridge ever go off by being exposed to a small amount of heat?
2) Should one have fallen into the fire would it have just gone 'pop' or would it have actually 'shot out'?

I remember in elementary school this kid telling us that he put a bullet in his dad's vice and hit the primer with a hammer and pin and shot a hole in the workshop...and I also remember our teacher calling 'bulls%&t' and saying that in order to actually travel a bullet needs an enclosed space like a rifle barrel to propel it forward. A cartridge out in the open might explode but the casing would just blow out and the bullet wouldn't go anywhere.

I know, who cares right? Well me and my mates do naturally!

Any experts out there?

 

[SRock]

1) Would a cartridge ever go off by being exposed to a small amount of heat?
2) Should one have fallen into the fire would it have just gone 'pop' or would it have actually 'shot out'?

1) Define small amount of heat. Hanging over a fire momentarily, no. Dropped in a fire, yes a cartridge can and will go off if left in a fire. It will cook off the same way if left in the chamber of a very hot gun.

2) Could go either way. The casing could rupture without "shooting out" the projectile. However, the more likely scenario would have the projectile blown out of the casing. It could be life threatening at a close distance, but at a greater distance it would not. Part of the lethality of a bullet is the immense pressure with which it is forced down the barrel of a gun. This is what gives it range and stability. When Gun powder fails to deflagrate properly and generate the pressure within the case needed to launch the bullet the powder burn eradically and the force that the bullet exits the casing could/wold vary greatly.

Tried to keep it short and sweet. Hope this helps.

 

[thunderball]

1) Define small amount of heat. Hanging over a fire momentarily, no. Dropped in a fire, yes a cartridge can and will go off if left in a fire. It will cook off the same way if left in the chamber of a very hot gun.

2) Could go either way. The casing could rupture without "shooting out" the projectile. However, the more likely scenario would have the projectile blown out of the casing. It could be life threatening at a close distance, but at a greater distance it would not. Part of the lethality of a bullet is the immense pressure with which it is forced down the barrel of a gun. This is what gives it range and stability. When Gun powder fails to deflagrate properly and generate the pressure within the case needed to launch the bullet the powder burn eradically and the force that the bullet exits the casing could/wold vary greatly.

A most thorough and scholarly answer sir! Thank you! I shall report at once back to the boys.

 

[michael.scheller]

Good explanation by Slagle.

Everytime I hear someone mentioning fooling around with rifle or pistols cartridges I always think of Johnny Unitas in my mind one of the greatest quarterbacks of all time. I read his autobiography when I was in 1st grade, shortly after it hit our school library shelves. When he was five, his brother had the bright idea that if you took a 38 pistol cartridge and hit the primer with a nail.... the casing from the cartridge ripped into Johnny's leg.

Now I find this, and discover Mr. Unitas did not write the autobiography I read and that there were numerous errors.
http://www.baltimoresun.com/sports/football/bal-sp.maese20oct20,0,6622775.column

 

[Roman414]

A bigger question...why you guys were sitting around the fire with whiskey in one hand and loaded weapons in the other! Not the best of combinations, mate.

 

[Joshua Da Silva]

This reminds me of the scene from Shoot em' Up when he puts the bullets between his fingers, holds his hand up to the fire and they all shoot out and kill the bad guy

 

[MrGuy]

The Mythbusters did a few myths on this subject. One was to place rounds in an oven, the other was to dump all types of ammo directly into a camp fire. Rounds discharged in both scenarios, but they weren't lethal. Some of the larger rounds (as in illegal in some states, according to them) could cause some big time damage, but not lethal. The idea is that a round just sitting on a surface will discharge energy both forwards and backwards, not just forward like when in a gun. Without focusing the energy one direction, out of a barrel, both the case and the bullet go flinging around with little real force behind them.
I hope this gives you a little bit of an answer, as I'm sure some of you have noticed I'm no expert, I'm just repeating words I heard on the TV
At any rate I'm sure it's safe to say, "Don't try this at home, ever"!

 

[chfair]

1) Define small amount of heat. Hanging over a fire momentarily, no. Dropped in a fire, yes a cartridge can and will go off if left in a fire. It will cook off the same way if left in the chamber of a very hot gun.

2) Could go either way. The casing could rupture without "shooting out" the projectile. However, the more likely scenario would have the projectile blown out of the casing. It could be life threatening at a close distance, but at a greater distance it would not. Part of the lethality of a bullet is the immense pressure with which it is forced down the barrel of a gun. This is what gives it range and stability. When Gun powder fails to deflagrate properly and generate the pressure within the case needed to launch the bullet the powder burn eradically and the force that the bullet exits the casing could/wold vary greatly.

Tried to keep it short and sweet. Hope this helps.

+1 to this answer


in a related story the guys i hunted with as a kid (father and his friends and their sons) had a very drunk friend stop by the ranch one night and at some point in the evening he thought throwing a whole box of .22 rounds in the fire would be a good idea. when all the soberish people realized what had just happened they all scattered and ran for cover. in fact the rounds did start going off and projectiles came shooting out of the fire. though a good amount of what shot out were the bullet casings and from what i understand the danger was not really that high given the low caliber bullets and the casings for the most part splitting apart when they went off. dangerous yes, life threatening? i would say mainly depends on the caliber round and where the projectiles managed to hit a person.

all in all i will say leave it to someone else to "test" this kind of thing if it must be tested.

 

[crankymoose]

1) Define small amount of heat. Hanging over a fire momentarily, no. Dropped in a fire, yes a cartridge can and will go off if left in a fire. It will cook off the same way if left in the chamber of a very hot gun.

2) Could go either way. The casing could rupture without "shooting out" the projectile. However, the more likely scenario would have the projectile blown out of the casing. It could be life threatening at a close distance, but at a greater distance it would not. Part of the lethality of a bullet is the immense pressure with which it is forced down the barrel of a gun. This is what gives it range and stability. When Gun powder fails to deflagrate properly and generate the pressure within the case needed to launch the bullet the powder burn eradically and the force that the bullet exits the casing could/wold vary greatly.

Tried to keep it short and sweet. Hope this helps.

A bigger question...why you guys were sitting around the fire with whiskey in one hand and loaded weapons in the other! Not the best of combinations, mate.[/QUOTE]

+1

 

[thunderball]

A bigger question...why you guys were sitting around the fire with whiskey in one hand and loaded weapons in the other! Not the best of combinations, mate.

Of course you're right but it wasn't exactly like that. The four of us didn't have any weapons at all until these two intrepid hunters sat down. After holding them up for us to see, both of them actually propped their rifles against a huge rock beside where we were sitting with muzzles skyward (chambers hopefully empty)...but then of course one of them reached over, pulled the clip out as I mentioned and started pulling out cartridges over the fire (our only light source) as though we'd never seen one before. The whole thing just sort of 'happened' and was thankfully over in minutes and they just walked off.

Having said that though, your advice is of course very wise!

 

[stobes21]

Basic physics tells us that if the powder in the cartridge ignites, it will exert pressure in all directions. In a proper firearm chamber that pressure is only allowed out one way, and in the process sends the bullet down the barrel.

Outside of a chamber though the gas will escape via the weakest point in the cartridge. It is possible that would be by rupturing the case wall. It is also possible, especially with reloaded ammunition, that it would push out the primer and escape through the primer hole. However, it would more likely be by separating the bullet from the case and escaping out the neck. Given that bullets almost always have more mass than the brass case they are attached to, this would result in a small movement by the bullet and a larger movement of the case. Of course this may change based on the position of the cartridge in the fire, the speed of the powder burn, etc.

The results may also be different depending on whether we are talking about black powder or smokeless. Black powder explodes and in doing so generates pressure. Smokeless powder, on the other hand, burns and the expanding gasses create pressure in the confined space of a firearm chamber. Thus, absent a firearm chamber the smokeless round will generate far less pressure and thus present relatively little danger when compared to the black powder round, which will still explode. It's kind of like the difference between burning kerosene and unleaded gasoline.

 

[thunderball]

Basic physics tells us that if the powder in the cartridge ignites, it will exert pressure in all directions. In a proper firearm chamber that pressure is only allowed out one way, and in the process sends the bullet down the barrel.

Outside of a chamber though the gas will escape via the weakest point in the cartridge. It is possible that would be by rupturing the case wall. It is also possible, especially with reloaded ammunition, that it would push out the primer and escape through the primer hole. However, it would more likely be by separating the bullet from the case and escaping out the neck. Given that bullets almost always have more mass than the brass case they are attached to, this would result in a small movement by the bullet and a larger movement of the case. Of course this may change based on the position of the cartridge in the fire, the speed of the powder burn, etc.

This makes good sense to my mind...excellent explanation sir!

 

[Roman414]

Sounds like the most likely danger would be getting hit in the eye by a fragment of hot brass...can you say, "Itai!"

 

[Bertilak]

Basic physics tells us that if the powder in the cartridge ignites, it will exert pressure in all directions. In a proper firearm chamber that pressure is only allowed out one way, and in the process sends the bullet down the barrel.

True, but a hand grenade is not constricted to one direction and even so it would be a "bad thing" if it went off in your camp fire. Now a bullet has less powder so will be less dramatic, but if just one piece of shrapnel from the casing goes in just the right (wrong?) direction it could be pretty bad.

 

[thunderball]

...can you say, "Itai!"

 

[stobes21]

True, but a hand grenade is not constricted to one direction and even so it would be a "bad thing" if it went off in your camp fire. Now a bullet has less powder so will be less dramatic, but if just one piece of shrapnel from the casing goes in just the right (wrong?) direction it could be pretty bad.

See the distinction between powder that explodes and powder that burns in my post. They don't use smokeless gunpowder in hand grenades for a reason. A black powder cartridge would be much more akin to the hand grenade example. As you pointed out though, even there the scale is far different.

Nonetheless, I was not suggesting that nothing bad would happen. Throwing live ammo in a fire or hitting the primer with a nail is stupid, reckless, and may well cause injury to bystanders. But a bullet flying out at velocities like those coming out of a gun barrel is clearly impossible.

 

[Bertilak]

Nonetheless, I was not suggesting that nothing bad would happen. Throwing live ammo in a fire or hitting the primer with a nail is stupid, reckless, and may well cause injury to bystanders. But a bullet flying out at velocities like those coming out of a gun barrel is clearly impossible.

Big coincidence! Shortly after my above post I spotted a Mythbusters repeat where they did just that -- throw a bunch of live ammo onto a fire. Lots of shrapnel put holes (more like dents) in some boards they had set up around the fire. There conclusion? Pain and blood but not lethal.

The lead didn't go anywhere but the casings did the damage.