Mark III barrels cracking.

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tomiswho

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The indication in that post was that approximately 60k rounds had been fired thru those rental guns. I did a little math, figuring $22/500rds and that means an expenditure of over $2,600 on ammo.

I'd think it would be prudent to think "preventive maintenance" and replace the guns prior to this point....

I'd be happy if my investment in a sub $300 Ruger .22 auto lasted half that long..... more than a lifetime of use for me!
 

raw6464

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tomiswho":tangf280 said:
The indication in that post was that approximately 60k rounds had been fired thru those rental guns. I did a little math, figuring $22/500rds and that means an expenditure of over $2,600 on ammo.

I'd think it would be prudent to think "preventive maintenance" and replace the guns prior to this point....

I'd be happy if my investment in a sub $300 Ruger .22 auto lasted half that long..... more than a lifetime of use for me!

A throw away gun is never a good thing? A gun should NEVER crack and if this gets any traction Ruger will never sell another one and your $300 one will be worth $2.... maybe.

But maybe your "preventive maintenance" will get some traction on those who never field strip theirs.
 

Hobie

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I've seen some MK Is used in military training that had far in excess of that number of rounds put through them. I'd like to know what's up, too.
 

wwb

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tomiswho":14lgpzo1 said:
The indication in that post was that approximately 60k rounds had been fired thru those rental guns......

From an engineering standpoint, 60,000 cycles to failure (and the failure actually started some time before that; the crack simply grew larger and more apparent in the ensuing cycles) is considered LOW cycle fatigue failure. It is a clear indication of inadequate material (too notch sensitive) or a poorly placed stress riser (the situation we have here). Low cycle fatigue is governed primarily by material ductility, and the typical firearm steels are high strength, but not very ductile. 2,000,000 cycles to failure or more is considered high-cycle fatigue. Less than 2,000,000 cycles to failure is mixed behavior..... governed partly by ductility and partly by strength.
 

Geezer

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I have been following this story. No one knows when the cracks happened. One was discovered and the other two were checked and the cracks were found in them, too.

At how many rounds would most people be OK with the crack? 10,000? 25,000? 60,000? I would think that most of us would say that any cracks would be unacceptable. Would anyone have bought one of these MK III's if Ruger said that the receiver would crack after X number of rounds? I doubt it.
 

tomiswho

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60,000 rounds..... What are the comparable specs for weapons submitted to our military for comparison? How long are they expected to last? For example, from Beretta: "The average durability of M9 frames is over 30,000 rounds. The average durability of M9 locking blocks is 22,000 rounds. "

wwb - I think you should list a disclaimer with your engineering data... talk about the fact that "cycles to failure" MTTF, and other factors depend greatly on what is being tested and primarily the expectations of the designing engineer. The 1,000,000 you used is arbitrarily used to establish a "rate":

Mean Time To Failure (MTTF)

MTTF is a basic measure of reliability for non-repairable systems. It is the mean time expected until the first failure of a piece of equipment. MTTF is a statistical value and is meant to be the mean over a long period of time and large number of units. For constant failure rate systems, MTTF is the inverse of the failure rate. If failure rate is in failures/million hours, MTTF = 1,000,000 / Failure Rate for components with exponential distributions.

Technically MTBF should be used only in reference to repairable items, while MTTF should be used for non-repairable items. However, MTBF is commonly used for both repairable and non-repairable items.
 

wwb

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MTTF (Mean Time To Failure) is irrelevant in theis case... a .22 rimfire round will add the same cumulative fatigue damage regardless of the time span.... cycles to failure is the only concern. For a minor, repairable/replaceable part, a low number of cycles to failure may be acceptible.

I'm not sure where you got the figures for the M9, but they sound awfully low. I'm not certain of the requirements that it had to meet, but in Vietnam, we had pre-WWII 1911s that had to have seen 100,000 rounds or more... they saw service in WWII, Korea, and Vietnam, as well as having been issued for training stateside in the interim. I recently sold a Ruger Red Label shotgun that had over 75,000 rounds through it, and bought an SKB 85 TSS, as it is a more serious competition gun. A shooting buddy has an 85 TSS with over 100,000 rounds through it, with no failures yet.

And, yes, cycles to failure is a statistical figure. In the engineering profession, unless otherwise stated, it is generally assumed to be a B-10 life... in other words, out of a large sample, 10% would be expected to have failed by the given number of cycles, while 90% would live past this point. In an extremely critical application, a B-2 life or even a B-1 life may be specified. As a side note, for ferrous materials, fatigue failure is generally a log-normal distribution... if I had my notes handy, I could give you the Weibull slope of a typical fatigue failure distribution for ferrous materials.

MTBF is, in this case, irrelevant. It applies only to recurring failures in a repairable system, and is generally associated with MTTR (Mean Time To Repair). MTBF and MTTR are used to calculate probability of mission success within a given time window.

If you feel like learning a whole bunch about metal fatigue (both ferrous and non-ferrous), get a copy of SAE standard J-1099. I was on the committee that originally wrote 1099 back in 1975... and, until I retired, I was an ASQC (American Society for Quality Control) CRE (Certified Reliability Engineer), so I'm not just blowing smoke up your skirt.
 

tomiswho

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As a mathematician, I bow to your engineering experience, yet don't try any statistical funny business.... :lol: :lol:

My whole point in this thread is that the expectation of a low priced Ruger firearm lasting 60,000 rounds as a rental without failure is unreasonable, and neither we, nor Ruger should be overly concerned. I doubt if the pistol was designed to last that long, and if it were it would cost much more.

Sure, if I worked at Ruger, I would want to take a look and see why the failure occured, but I would feel no guilt if I were the production supervisor for these guns.

Now I'm thinking I should be able to drive my car 500,000 miles without any trouble..... or else the manufacturer should be liable....

It was a LONG time ago I studied metallurgical engineering and belonged to SAE, but that was a different lifetime.
 

wwb

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No statistical funny business....an "acceptable" product life should be part of a design spec. The original Standard Auto and the Mark II never had this problem. You add a stress riser to an existing design without making any compensating design changes, and you no longer have an acceptable product life. Lots of springs, pins, and other widgets may fail and be replaced in the course of a pistol's life, but the receiver should still be intact when the pistol is retired. Bad engineering - or, maybe, NO engineering.
 

Redm2

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I wouldn't put too much stock into the number of the said rounds these guns have cycled....

A few things:

"These were bought about 2 years ago and see a lot of use."

"I would guess these guns are have somewhere between 60K and 80K rounds through them."

Based on the fact he is saying "about, guess, and somewhere between" there is no way to tell how much use these guns have.

In 3-4 times shooting mine over a 2 week span (1/2hr min and 2hr max) I have put between 800 and 1000 rounds through my Mark iii. It doesn't take long to burn through 1k rds. These guns could have easily seen more than 100k.
 

tomiswho

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wwb,
I think you may have hit upon the cause...
"NO engineering."

My guess is that the "receiver" has always been made as BR drew it.... turned? milled? And there were never any tests or analysis' made.... My Standard from 1968 hasn't cracked.....
Tom
 

raw6464

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At the end of the day the receiver should never crack under normal operating conditions... but they did. MTBF/MTTF are all good product stats for washing machines, not for guns that can blow up in your face and kill you.

The number one question is this a safety hazard to the user? Considering all the variable conditions and ammo used is an answer Ruger needs to get their arms around and come up a response, both short and long term. Ignoring it is not an option.
 

meanc

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Prime example of user neglect.

Definitely not something more responsible owners/shooters will have to worry about.

I'm more than certain a simple recoil spring change would have prevented the problem.


Ruger will probably do something, but don't think they are at all responsible.

I guess Will Rogers said it best...

"Common sense ain't so common"
 

chet15

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Sounds like a heat treating issue with a "batch" of pistols. Doesn't mean all three million + of Ruger's .22 pistols are bad.
Chet15
 

raw6464

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meanc":3vlcblby said:
Prime example of user neglect.

Definitely not something more responsible owners/shooters will have to worry about.

I'm more than certain a simple recoil spring change would have prevented the problem.


Ruger will probably do something, but don't think they are at all responsible.

I guess Will Rogers said it best...

"Common sense ain't so common"

Three receivers cracked at the point Ruger drilled extra holes for an LCI and you are "more than certain" they cracked because they had weak recoil springs?

If weak recoil springs can causes the receivers to crack... this gun is a piece of crap.

Your right common sense ain't so common.
 

raw6464

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chet15":3ifnjznm said:
Sounds like a heat treating issue with a "batch" of pistols. Doesn't mean all three million + of Ruger's .22 pistols are bad.
Chet15

The guns where made a year apart.
 

Geezer

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I'll bet these folks wouldn't be so understanding and defend Ruger if it was their Mk III that cracked. I know that I wouldn't.
 

wwb

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meanc":3c9976jz said:
......Ruger will probably do something, but don't think they are at all responsible.......

Over the course of my engineering career, I served as an expert witness in about a dozen product liability cases (always on the company's side, of course). We had to defend our product against people who misused it, killed or injured somebody, and claimed it was the defective product that caused the death or injury.

I would take one quick look at this, and my advice to the company would be to recall 'em all and fix 'em all...... this is an obvious design flaw, and no way could it be defended if an injury resulted. Fortunately, even if the receiver cracked completely in half, it doesn't appear to have the potential for injury; the pistol would most likely fail to fire and/or separate into two pieces.
 

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