Odds please

[RetiredUSNChief]

Was this the first time you reached for my drill index, opened it, and the second to largest bit in a standard index fell out, which then struck a primer on its way to the floor, setting it off and making you jump out of your skin?

If so, then the odds are 1 in 1.


Now, if you were to repeat the sequence, only this time the bit does NOT strike a primer and set it off, then the odds would be 1 in 2...

 

[mr wack]

I don't know, too early in the morning to be thinking about such things.
Now ask me the odds of finding my fav coffee cup after the good woman put it up last night and I would say about 1 in 0 chance,,,,

 

[230RN]

A fun little thought-experiment, ain't it?

Bobson figured,

Mathematical odds? Depends on the open floor space. Average garage is about 22' x 22' (or 484 sq ft). A primer is, what, a quarter-inch across? Lets say 0.25 sq in. There are 144 sq inches per sq foot, multiplied by 4 since we're dealing with quarter-inches, multiplied by the 484 sq ft from before, equals 278,784 primer-sized units in one average garage. How much floor space was actually available, though? Then again, you dropped the bit near the toolbox (and were mathematically likely to), which means much of the open garage space is irrelevant.

Area of a small primer (0.175" diameter) is 0.024 square inches, not 0.25 square inches.

Area of a large primer (0.210" diameter) is 0.035 square inches.

Oh, well. What's an order of magnitude between friends?

But it's a conceptual start on the "problem," which is what I think OP was getting at and putting it in the form of a survey.

Don't know what effect there is on a drill point hitting a primer with the cup up versus the flat side up, but I guess you can assume 50% of them are cup up and the other half cup down.

And there are other variables, such as hitting the primer off-center so it won't go off, and whether they're hard primers or soft ones, the chances of the drill landing with one end hitting the primer. And what the primer mix is. I guess you can assume a drop height of three feet, but I didn't bother to weigh "the second largest bit" in my kit.

Hatcher has a table of primer sensitivities in terms of inch-oz of energy in Hatcher's Notebook page 394 for a starting point for guesstimation of numbers for sensitivity. I would guess around 20 in-oz for a starting point in order to reliably fire a primer. He has another detailed table somewhere regarding this, but I don't feel like digging around in the book that much right now. I need to make some coffee.

But the real problem here is in assessing all the variables and then subjecting the problem to experimental test to refine, eliminate, or add variables. Insurance actuaries have the luxury of having data ready-to-hand for car accident likelihood which includes such variables as age of driver, driver ed classes, etc etc etc.

We don't, so have at it.

I'm no fun at parties, either.

My best off the wall guess is 1 in 100,000, so I voted with Bobson anyhow.

Now the real go-no-go question is, should the OP go out and buy a lotto ticket since he was "lucky" enough to set off a primer with a drill point? Or should he not go out and buy a lotto ticket because he was unlucky enough to set off a primer with a drill point?

O, Fortuna, velut Luna...

Terry, 230RN

 

[Zaydok Allen]

I think a better question is what are the odds that there will be a major accident at your reloading bench that causes you sever and debilitating injuries, and/or possibly burns down whatever structure you choose to reload in?

If loose primers on the floor do not warrant immediate action on your part, and are indicative of your overall handling of explosive material, I'd say pretty high. If you were unaware that the loose primers were on the floor, then a trip to the eye doctor is a good idea.

Glad you weren't hurt. Sorry to be a bit of a jerk, but this is a scary thread to me that screams "SAFETY!". And I tend to be rather lax about safety, sooooo there ya go.

 

[Bush Pilot]

I think a better question is what are the odds that there will be a major accident at your reloading bench that causes you sever and debilitating injuries, and/or possibly burns down whatever structure you choose to reload in?

If loose primers on the floor do not warrant immediate action on your part, and are indicative of your overall handling of explosive material, I'd say pretty high. If you were unaware that the loose primers were on the floor, then a trip to the eye doctor is a good idea.

Glad you weren't hurt. Sorry to be a bit of a jerk, but this is a scary thread to me that screams "SAFETY!". And I tend to be rather lax about safety, sooooo there ya go.

You do realize that a primer going off under this situation isn't going to have the same affect that a 500 lb bomb dropped from a B17 would have? I've dropped live primers I couldn't find and was mad at myself because I had to open up another package of primers to finish my project.

 

[JFtheGR8]

Every time I drop a hammer a primer goes off.

I am fun at parties. [emoji6]


Sent from my iPhone using Tapatalk

 

[Zaydok Allen]

You do realize that a primer going off under this situation isn't going to have the same affect that a 500 lb bomb dropped from a B17 would have? I've dropped live primers I couldn't find and was mad at myself because I had to open up another package of primers to finish my project.

Thanks for clearing that up. If you don't think it's a safety concern that's fine. The point is that in the wrong circumstance, it could cause a bigger accident.

For instance, my reloading area is carpeted, and I have two cats. If I were to allow stray primers to lay around on the floor, and the cat decides to knock something over, which they do, and it detonates a stray primer, there is a possibility, however small, that my carpet could light on fire. If I'm at work, my house could be gone before the fire department gets there. I am extremely cautious with anything that burns, detonates, or sparks, because the potential ramifications could be extreme.

 

[Rule3]

Now lets say that in this scenario the primer did not go off. Then you could write a thread in the Reloading section about how XYZ primers sux and are no good and have a failure to ignite,

Then everyone would boycott that brand! and the thread would go for ever!

 

[ny32182]

The mathematical odds of it happening does not equal 100/(the number of possible outcomes).

I wouldn't make a habit of leaving loose primers rolling around on the floor, myself. Even one has some punch to it if you detonate it in exactly the wrong circumstance.