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Falling Casing Setting Off Round On The Bench


Mathew

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I've heard one story like this, but then witnessed it recently. I'm kind of curious if this is a one in a million thing, or if other people have seen this.

Guy next to me at the range is shooting with an open box of .40 on the table. Casing exits the pistol, bounces off the wall of the booth, off the ceiling, lands on the primer of one of the rounds in the box on the table.

Round indents the table and comes to rest on the floor about a foot away. Styrofoam box gets blasted in half with pieces all over the table. Casing ruptures and fires straight up into the ceiling breaking through the plastic cover around the light and breaks the florescent bulb. Nobody was hurt, but wow was the look on his face priceless.

I keep my ammo covered when I shoot now. ;)

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Last summer a tray with several loaded rounds fell off my bench.

One of the rounds detonated when it hit the floor.

At first I thought the bullet must have landed base down allowing the primer to strike some debris.

However, closer examination revealed that the bullet landed nose first.

It appears that the primer fired from the inertia of a short fall onto a plywood floor.

I had never seen ammo detonate outside a gun before and I would not have thought it possible in the scenario I just described.

However, judging by the number of reports I have seen, it happens more often that you would think.

Sometimes they go off by accident.

Sometimes they fail to go off when you want them to.

Manufacturing primers is a difficult proposition.

It is a fine line between making them too sensitive or not sensitive enough.

I think manufacturers err in both directions.

Tls

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I heard a shot that didn't sound like normal gunfire and looked over and saw the aftermath, then played CSI from there. I was in the booth next to him and they are clear plastic. The other story I heard was a close friend of mine that watched the same thing durring a match but he actually saw it happen.

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Brian did it, I've done it, it happens. Tlshores, the one that fell nose-down? Probably powder compression rather than primer inertia. Bullet sets back into case until it compresses powder, setting it off.

Look, primers are designed to detonate. If we use or abuse them too far out of their design parameters, they're going to protest.

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I've seen it happen at an ICORE match when the shooter was reloading and when he ejected a moon with at least one live round it struck the ground,(probably a stone) and went off. No one was hurt and it does not happen very often but it does happen. :ph34r:

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Inadvertant hits to primers happens more than you would think.

The range where I used to go to had it happen to one of the counter people. He chucked a live round and it just happened to land wrong and the round went off.

About 2-3 years ago when I worked at a police academy a round discharged (IIRC) when it fell on the gravel/rocky ground of our range. One of the cops was (very) slightly injured. Our CSI-type people (SID) came in and had to investigate the whole thing.

I think it's more of a couple thousand to one chance that it will happen. :D

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I saw it happen one time when I had a guy unload and show clear. Scared the crap out of both of us. Niether of us knew what happened at first. I had him show me the chamber again and the gun was completely empty. Then we noticed one of his socks had powder burns. I suspect his shorts may have had powder burns too. (Or was that my shorts) :lol:

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You guys are all describing scenarios where there is at least some notable weight/mass/momentum/energy transfer involved. This post is about an empty casing supposedly setting off a round in an ammo box sitting on the bench.

Sure sounds like a million to one situation to me. I'd be willing to bet a guy could stand there for a week and never manage to replicate it as described.

What if we were talking about an oak leaf drifting into the box? A rubber ear plug falling onto the ammo? A falling cotton ball bumping the primer and setting off a loose round? That would be almost impossible, right?

My point is, there's gotta be a threshold where there just simply isn't enough energy transmitted to light off the primer. A falling piece of empty brass doesn't transmit much energy.

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No, but if the primer being struck was the most sensitive one of the production batch, AND the falling case had the rim strike it so that all the force of the fall was transmitted directly to the primer, AND and round was securely held so it could not move, we'd have as close to 100% transmission of the case's force delivered to the primer. Weird? Yes. Possible? Obviously. Likely to happen again? Can you say "lotto odds?"

S**t happens. That's why we keep the muzzle pointed in a safe direction. And a lot of other things we do.

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When my youngest son was shooting he ejected a round at "unload, etc" and the live round from his chamber hit something on the ground ( a piece of brass, as stone?) and detonated. Since there was nothing to hold the pressure the brass blew out and the bullet traveled straight up a fell back down.

Its true, stuff happens.

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My point is, there's gotta be a threshold where there just simply isn't enough energy transmitted to light off the primer. A falling piece of empty brass doesn't transmit much energy.

Hmmm...... a small very light piece of metal moving at a pretty fast clip that hits a primer and detonates it.... sounds like a firing pin. ;)

(remember, the empty case was EJECTED, not just falling; it was probably bounced off the wall at a pretty good velocity)

Improbable? Yes. But certainly possible.

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I have all of the peices of such a detonation. I was reading this thread and explaining to a new shooter on thursday. We went shooting on Friday and boom off went a case in the box. I gathered all of the pieces and brass. Here are some of the incriminating pictures.

We where shooting from a covered area of the range, the case bounced off the cover and hit the box about 10 ft away. Yes the bullet tray was out of the box with the bullets exposed.

Lesson learned, Always wear your safety glasses when you are on or near a shooting range.

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If you've been hit by flying brass (and who hasn't... except for you wheelie gun only guys :) ), you know those suckers carry some energy. Pretty amazing stuff, though, I have to admit :) In Tactical 1's example, I'm a little suprised the case didn't rupture - which is what I've been lead to believe should happen on an out-of-gun detonation - in fact, this was an often discussed topic on rec.guns a long time ago - what happens if you throw a live round into a fire, etc... Hmmm.....

I guess we all switch to CCI primers, now, eh?? :lol:

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drift on...

what happens if you throw a live round into a fire....

If cold or wet, we'll occasionally burn trashed targets and target sticks out at our range, using a 55 gallon drum with the ends cut off. Nobody deliberately tosses live ammo into the fire, but the gravel surfacing our range is full of old rounds. Detonations are so common that the old hands don't even flinch as they warm their hands. No shrapnel injuries. I can't say if that is because the cooked off rounds are buried aready or because the metal of the barrel holds them.

drift off...

edited to add that I also don't know if there aren't shrapnel injuries because there isn't any shrapnel...

Edited by kevin c
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Another note is that just fired brass has a lot of thermal energy (i.e. very hot) many people have been burned by hot brass. (I personally got a 3rd degree burn when one stuck on my shirt collar when I was ROing another shooter.)

Could the heat of the brass set another round off if the brass lands and stays in contact with the primer? Seems it would be possible.

I would say an additional lesson learned don't leave open boxes of cartridges on the bench when you are shooting...

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I would truly doubt the cookoff scenario. Even firing full auto and then leaving a round in the chamber behind a closed bolt doesn't always cause cookoffs. I'd have to see the Mythbusters test this one before I'd believe it.

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Cook Off??

Let us look at the conditions of my previous post with examples.

1) Locaton, Michigan in December. Tempatures slightly above normal on the day in question, low to mid 30's.

2) Mass of case and tempature of case. I agree that the ejected case is hot to very hot. But to transfer enough heat to cook off a live primer in the instant it contacts the live case. I don't think it is that hot.

All of these conditions, I feel, do not indicate cook off. I believe force was the determining factor. I would not believe that an ejected case had that much force to detonate a live round after traveling 10 ft. I believe it now. I will always cover my live rounds from now on.

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I would truly doubt the cookoff scenario. Even firing full auto and then leaving a round in the chamber behind a closed bolt doesn't always cause cookoffs. I'd have to see the Mythbusters test this one before I'd believe it.

I'm not saying it did or could, just wondering about it. I know the hot case would have to sit in contact with the primer for at least a few seconds. (The burn I got contact was only about 3 seconds and the case was trapped by my shirt collar, so it just maded me curious.)

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