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Question for the Engineers & Scientists ?

4K views 47 replies 33 participants last post by  C hawk Glock 
#1 ·
There are frequent posts about the "break-in period" for new semi-automatic handguns. Most wonder about how many fired rounds predict reliability. A worthwhile question, since one's life may be involved.

From a PURELY STATISTICAL STANDPOINT (and I barely passed my college statistics course several decades ago) is there an answer?

If a brand new semi-automatic handgun, properly cleaned and lubricated, using fresh quality ammunition, fired the first 15 shots without any malfunction, what is the statistical probability it will fire the next 15 shots without malfunction?

Does that probability increase significantly if it fires the first 100 shots without malfunction. If so, how much?

If it isn't too complex, please show us the formula....

THANKS.

JERRY
 
#2 ·
Simplistic probability dictates that the probability of the first 15 rounds fired is 1 (P(fire) = 15/15 = 1). Given there are no other factors influencing the outcome then the probability of the next fifteen rounds firing would also be one (P(fire) = 30/30 = 1)

At this point your probability can't increase, it can only go down. If your first 100 shots are fired without incident, they you're still at 1. If however, you have a misfire somewhere in the next 100 rounds, then your probability is now P(fire) = 199/200 = .995 Now from here it can go up. For example if you fire the last 800 rounds without incident they your final probability for 1000 rounds is P(fire) = 999/1000 = .999
 
#5 · (Edited)
Voltage & Wattage are different <g>

Simplistic probability dictates that the probability of the first 15 rounds fired is 1 (P(fire) = 15/15 = 1). Given there are no other factors influencing the outcome then the probability of the next fifteen rounds firing would also be one (P(fire) = 30/30 = 1)
Have to disagree with your application of the formula.

A gun that's 95% reliable (i.e. misfires on one out of 20 shots, average) has a 46% chance of firing fifteen consecutive rounds without a malfunction. The 15/15 that you stated in the first equation is NOT "P(fire)" (a probability) - it is an outcome.

You could, after your first 15 shots, conclude that the probability of a misfire is something less than 1/15 (0.0667), so the probability of the next 15 shots being successful is .9933^15 (= 35.5%) or better.

If you've fired 100 consecutive good shots, then the probability of a misfire has been established at less than 1/100 (0.01). So, the probability of the next 15 shots being successful is 0.99^15 (= 86%) or better. The chance of the next 100 shots being flawless, on a purely statistical basis, can only be determined to be around 36% (0.99^100) or better. No matter how many times you fire a gun, you can never prove that it has a 100% chance of firing on the next shot, 'cause it just ain't so.

Hope this helps.

Regards,
Jim
 
#3 ·
I like simple.
The next logical step would be to break this down by ammunition type and individual magazine.
 
#6 ·
Really not a question that can be answered simply. There are too many variables involved. Caliber, material the gun is made out of, and the manufacturing tolerances used are all going to play into it.
 
#7 ·
As I like to say, every break in shot puts you one closer to the first failure.

For a group of people as safety obsessed as to fear an empty gun shooting us, it's a paradox how much we fear a loaded one going "click".
 
#8 ·
I am not a scientist nor do I play one on TV, but my answer is very simple. Everytime you pull the trigger there is a 50% chance it will work and another 50% it will not. It does not matter if it is a Glock, HiPoint, etc. I hope this helps. God Bless :smile:
 
#26 ·
Actually, the "average" handgun will NOT fail to fire 50% of time. If you have one like that = get it fixed ASAP!
The other variable in this is the cleanliness of the gun. If you were to actually run this reliability test, I would think you would want to clean it after each shot to remove the variable or powder residue build-up so that you are truly taking a measure of the mechanical component failure rate, not the rate at which the firearm becomes too dirty to be reliable.
 
#9 ·
Missed in all of the above to some extent, the science of statistics involves conducting an experiment, collecting results, collating and analyzing the results, and drawing inferences, usually in the form of probability, from the results of the experiment.

What can be gleaned from an experiment depends on whether or not the experiment is adequate to the task of arriving at an answer.


Firing 15 shots and collecting a single percentage of results really gets you nowhere. Similarly, firing a single series of 100 consecutive shots and trying to extrapolate to the future from what is really only one result, won't get you anything.

Finally, nothing but experiments with lots of shots fired can incorporate the effects of wear, tear, accumulated dirt, on long term performance, which common sense tells us will degrade over time. In short, no matter what the results are with the first 100 to 1000 rounds, mechanical devices degrade with time and the results for the second 1000 rounds will possibly be a bit (or perhaps a great deal) worse.

Ever notice how the auto- dealers like to tout the numbers for "initial reliability" or "initial customer satisfaction." These say nothing about what the car will be like after 3 years. Even a piece of junk might hold together for 10,000 miles.
 
#11 ·
Oh, you met my Algebra teacher.
 
#13 ·
Thing is, it isn't always "linear" like that. Some guns are super reliable up to a few hundred rounds, then have some part break that renders it inoperable. Your statistical projections would be useless in such an instance.

It's also why it's always worth waiting, with new guns, for someone to test it out for several hundred to thousands of rounds to see if something breaks. It's easy to watch a video or text review where the author fired maybe 100-200 shots and had no failures, but it's going to suck when you buy it thinking it is reliable, only to have a trigger bar, recoil spring, or something else fail after 300 shots.
 
#14 ·
Thing is, it isn't always "linear" like that. Some guns are super reliable up to a few hundred rounds, then have some part break that renders it inoperable. Your statistical projections would be useless in such an instance.

It's also why it's always worth waiting, with new guns, for someone to test it out for several hundred to thousands of rounds to see if something breaks. It's easy to watch a video or text review where the author fired maybe 100-200 shots and had no failures, but it's going to suck when you buy it thinking it is reliable, only to have a trigger bar, recoil spring, or something else fail after 300 shots.
This really raises an interesting question, I think. I've had one gun in which the recoil spring and guide rod failed dramatically after about 3 K rounds. I have another where I had to replace a manufacturer's original recoil spring with a Wolf spring, maybe with only about 1 K through it.

These experiences have made me think twice and three times about doing a lot of shooting with an SD gun. It is sort of like keep two guns handy, just in case. Or, go the revolver route. (And neither gun was a "poor quality" el-cheapo.)

My experience would lead me to advise keeping 2 handy or sticking with a revolver. I do neither though, and I can't say that I really am all that comfortable relying on my two auto loaders.
 
#15 ·
If a brand new semi-automatic handgun, properly cleaned and lubricated, using fresh quality ammunition, fired the first 15 shots without any malfunction, what is the statistical probability it will fire the next 15 shots without malfunction?
If the gun in question is a "High Point", there is an excellent probability that something will break in the next 15 rounds.

Does that probability increase significantly if it fires the first 100 shots without malfunction. If so, how much?
Practical application and experience with various "High Point" pistols, would seem make that fact a near impossibility. While the math may seem to make it possible that it could in fact happen that the High Point could shoot 100 rounds without malfunction, it would be about as possible as walking both coasts and finding an ancient gold coin washed up on the beach. Sure it happens, but not often enough to be of any real concern.
 
#16 ·
If it malfunctions, it will be right when you need it the most; ie Murphy's Law.
 
#39 ·
There ya go!

Actually, in the world of manufacturing they also use some vodoo magic called SPC, which stands for Statistical Process Control. They think that they can predict a point at when a failure occurs by measuring the trend toward a failure.
Example, if I fire 1000 rounds out of my glock, and measure the dimple made by the firing pin on the primer, I can determine the rate at which the pin is wearing out, and if I know at what dimension it will fail to cause a primer ignite, I can use SPC to predict how many more rounds before this happens. The same could be done fro gunk buildup on the slide. At some point it will build up to the point that the gun does not cycle properly and fails to feed. All I need to know is how much gunk each round deposits on the slide and at what poiint the slide will not move freely enough.


Simple, huh?
 
#19 ·
The MIM Factor.
You need to also factor in MIM parts which historically have catastrophically failed at a much higher rate than investment cast or forged/machined steel.
On the plus side - Usually when MIM (Metal Injection Molded) fails it fails rather quickly and dramatically AKA it's either a good MIM "part" (that will be serviceable) or there is a QC problem & it will fail in a big hurry.
 
#20 ·
ammunition type and individual magazine
Don't forget powder brand, FMJ versus HP, primers.....................I think Hopyard is correct anyway, since he answered the Train question............and studied the use of statistics in consumer advocacy. :image035:
 
#21 ·
Or you can just forget all the math...and carry two guns. IMHO you are better off with two smaller guns, than one big blaster. The probability of both guns failing during the same incident are virtually zero. And no reload is quicker than a "NY reload."

Just sayin'...
 
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#22 ·
This is a lot like trying to 100% test fuses. Instead of looking for a "pass" result, you want to test till "fail", which leaves the test article useless. Look for makers that use good materials and reliable processes. The internet has made it easier to gather accounts of a model repeatedly failing. Buy the proper tool, I won't buy a race or target gun for carry. And for the most part, you're gonna have to chip loose of a little money.
 
#23 ·
I generally adhere to a break in period of 300 or so rounds. If the gun performs well for that round count I consider it reliable. I make sure to fire as many rounds of the type of ammo I will carry int he gun as i can afford.

I consider the gun reliable if it fires those 300 rounds with out jamming or failing to fire in any way. If it does, then I contact the manufacturer and give them the chance to make it run correctly. If this can't be done, I get rid of the gun and get one that will run. I don't get emotionally attached to guns until they prove to me that they can be trusted with my life and the lives of my family.
 
#24 ·
My local Game Warden carries a Glock and the local LEO's I know all carry Glocks. They turn them into their armor about every 6 months for a check up.
They say the armor replaces every spring or small part that is prone to failure. (If this is the practice around the country, no wonder Glocks have a good service record.)

But as they say, even if the basketball shooter has a 90% record at the free-throw line; it's still 50-50 everytime he goes to the line.
 
#25 ·
...But as they say, even if the basketball shooter has a 90% record at the free-throw line; it's still 50-50 everytime he goes to the line.
"They" are mathematically challenged. :yup:

Regards,
Jim
 
#27 ·
SO, back to the original post/question.....

If the first 15 rounds from a properly cleaned brand new handgun fire without malfunction, does firing another 100 or 200 rounds for a so-called "break-in peiod" actually increase (or decrease?) the likelihood of the the next 15 rounds firing without malfunction -- from a mathematical/statistical standpoint? Or is that break-in concept just a "FEEL GOOD" consideration?

It would mathematically seem that the more rounds fired, the higher the probabability of some other part breaking or wearing out (spring, extractor, firing pin, etc.).

JERRY
 
#40 ·
SO, back to the original post/question.....

If the first 15 rounds from a properly cleaned brand new handgun fire without malfunction, does firing another 100 or 200 rounds for a so-called "break-in peiod" actually increase (or decrease?) the likelihood of the the next 15 rounds firing without malfunction -- from a mathematical/statistical standpoint? Or is that break-in concept just a "FEEL GOOD" consideration?

It would mathematically seem that the more rounds fired, the higher the probabability of some other part breaking or wearing out (spring, extractor, firing pin, etc.).
JERRY
To some extent I agree with this. Lets say that a certain brand of gun is known to need a spring replaced about every 500 rounds. Would those that advocate firing 500 rounds to certify the gun think that it's wise to run the 500 rounds though and figure the gun is good to go? I mean it worked the last 500 rounds right? So it's good to go.
To some extent every shot you fire move you one shot closer to a failure because nothing last forever, (except maybe twinkies).
 
#29 ·
And then after all is said and done and a scientific determination is made that the handgun is completely reliable....the homicidal maniac bad guy is running at you at top speed ready to hack your head off with a machete and you get a squib round due to a bad lot of ammunition. :dead:

:biggrin2:
 
#31 ·
I am NOT a engineer, but I did stay in a Holiday Inn Express last night and I can conclude that you people have to much time on your hands. Buy a Glock and carry a small BUG and dont worry about it.
 
#34 ·
This really is not a good question for engineers or scientists.
Engineers and scientists will solve the problem by adding thousands of variables to the equation and just end up complicating the answer.
It is a good question for applied mathematicians (stay away from the theoretical math people though because they typically don't have real world experience and will also complicate the answer, too).

Kilowatt3 provided the best answer to the original question using simple linear regression method statistics.

On a side note, if your firearm fired successfully 1000 times without any malfunctions right out of the box, I want to purchase it. :smile: (Just kidding)
 
#42 ·
This really is not a good question for engineers or scientists. Engineers and scientists will solve the problem by adding thousands of variables to the equation and just end up complicating the answer.
.......
Really? I take exception to that statement. Reliability and probability are intrinsically linked and reliability is the study of failure mechanisms and the prediction of failure. Reliability is a key component of any engineering discipline. Although the exact instant an item will fail can never be determined, an approximate idea of failure can be predicted.
 
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