Bullet setback

So the idea that someone said that someone reported that a setback of such and such distance will always cause the gun to blow up is just not true.
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It's a good bit more complicated than that. It depends on the caliber and the bullet weight in the caliber. Some calibers, the .40S&W being one of them, are more sensitive to setback than others, and a general rule of thumb is that in a caliber that is sensitive to setback a heavy bullet loading will tend to cause the highest pressure rises for a given amount of bullet setback.
I have said that I have personally tested several brands of 9mm ammo and deliberately set the bullets back far more than any repeated chambering could do (to the point of case bulging) and there were no signs of severe pressure increases; the guns did not blow up and I, obviously, was not killed, or at least I don't think I was.
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Assuming that you tested a wide range of bullet weights in loadings that already were fairly near max, then your testing is probably good evidence that the 9mm is not very setback sensitive. That actually makes good sense because I can't recall ever hearing of a catastrophic incident involving 9mm where setback was implicated.

HOWEVER, it's a serious mistake to assume that the test results derived exclusively from testing 9mm ammunition relates in any significant way to setback sensitivity in other pistol calibers.
 
Well, John, I surely won't argue that if a cartridge developed 138k psi, the gun would be toast and perhaps the shooter wouldn't do so well, either.

But again, we have a table from an unknown or uncited source, showing that deeply seated bullets of a certain weight in a certain caliber might run up pressures. I haven't run any firing tests with .40 S&W, but I did try to attain those short COALs, and was not successful with any kind of normal loading, at least with the cases and 180 grain bullets I used.

There is no mention of the type and weight of the powder charge used, or of how a round with a COAL of only 1" would go unnoticed when replaced in the magazine or would feed without jamming or of how a bullet seated that deep would not bulge the case enough to prevent chambering.

If the experimenter deliberately set out to use the right (or wrong) powder, with a maximum charge, with the bullet deeply seated by force, I suppose he could run up some serious pressures. But I simply don't believe that the amount of setback that would occur from chambering a round, even repeatedly, could force the bullet in deeply enough to get into those high pressure ranges. (Assuming that the pressure data is valid.)

Jim
 
But again, we have a table from an unknown or uncited source...
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http://www.thegunzone.com/glock/kb-notes.html
"“This was first confirmed via a European cartridge maker (Hirtenberger in Austria) from information given to me by a high level Glock representative. 1/10" set back can cause pressures to double from 35,000 psi to 70,000 psi." (The "me" in the quote refers to Walt Rauch.)

So now we're working with a known and cited source.
There is no mention of the type and weight of the powder charge used...
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Todd Louis Green's data (Todd has worked for at least two major gun manufacturers that I am aware of and is a certified armorer for at least 5 brands) indicates that the pressure rise can by a factor of 2.76 from 0.1" of setback.
http://greent.com/40Page/ammo/40/180gr.htm

The point is that IF a standard pressure round is set back 0.1" during feeding the pressure can rise to a dangerous level in some loadings of some calibers.
..., or of how a round with a COAL of only 1" would go unnoticed when replaced in the magazine or would feed without jamming... or of how a bullet seated that deep would not bulge the case enough to prevent chambering.
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1. It doesn't matter what powder was used or how much, the fact remains that setting back the bullet 0.1" CAN cause the pressure to double. There's a critical difference between "can" and "will". As you determined, it does not ALWAYS cause the pressure to rise dangerously--whether it does or not is dependent on the caliber and upon the loading.

2. Detecting the setback while loading the magazine assumes that the round is unchambered. If the setback occurs during the process of feeding the round into the chamber the shooter will not be able to detect it.

3. It may not feed if the setback is severe. However, that's certainly not a given. I have guns that will feed empty cases from the magazine.

4. It probably won't feed if the cases are bulged in the process of setting back the bullets. However, a few of the rounds from the picture in the OP have at least 0.1" of setback and don't exhibit any bulging or deformation.

Your testing in 9mm is very interesting and the results may be valuable in terms of assessing the risks of setback in 9mm--at least within the parameters of the testing you performed. However given that the testing was narrowly focused, the conclusion should be similarly narrow in scope. If that wasn't immediately obvious, it certainly is now that we have data from an ammunition manufacturer demonstrating that setback can certainly be dangerous in at least one caliber and loading.

By the way, here's at least one source that indicates that setback may even be an issue in some 9mm loadings.

http://www.thegunzone.com/glock/setback.html

"...the truncated cone hollowpoint bullet would ram the feed ramp with enough force to set the bullet back in the case reducing the powder chamber and resulting in much higher chamber pressure for the given load powder.

Some years ago (circa '93-'94) my Agency took Federal Hydra-Shok ammo out of the field for just this sort of problem in our 9 X 19mm S&W and Glock autos. They were blowing out the bottom over the feed ramp.

...I measured each round after it had been hand-cycled, and every single round was shorter. ... When I had fired 25 rounds I took the 25 round left over that had been chambered by the firing cycle and measured them. They were all also shorter, drastically shorter than the hand-cycled rounds."​

And here's another indicating that as little as 1mm (0.04") of setback in 9mm can result in a pressure increase of approximately 6KPsi--or approximately 15KPsi per 0.1" of setback. Given that ammunition that is most often rechambered is self-defense ammunition which is typically loaded near max, or potentially over max in the case of +P or +P+ , a 15KPsi increase in pressure could certainly be significant.

http://www.thehighroad.org/showthread.php?t=663075
 
Lets get on point....

Discussing how much setback in what caliber raises pressures to dangerous levels is fine. But its not the point in this case.

The OP's pic does not show rounds with "setback". It shows DEFECTIVE ammunition. Setback happens, (it should not happen), and it is a bad thing.

The OP shows rounds that came out of the box that way. That is NOT setback.

The maker has been contacted, (email) and the OP is waiting a reply.

The issue of setback is a real one, and it happens because the ammo is made "just good enough" and not "as good as it could possibly be". Over 40 years or loading and reloading auto pistol ammo has taught me that setback is not a necessary condition. Rounds that are manufactured correctly do not setback under ordinary conditions. A round that is made "right" doesn't set back, even after dozens of chamberings.

And, please, don't tell me its the gun. Its not.
 
I've spoken with both Todd and Dean about these types of topics in the past, and yes, bullet set-back is an issue and does cause higher pressures. In extreme cases, enough to cause case head ruptures. However, some that have been termed "set-back" related failures, I am highly skeptical of.

44 AMP is right, based on the info from the OP, this is an issue related to the ammo, not set-back. However, based on QC procedures, I have some serious questions as to "why" the pictured ammo is "short."
 
The maker has been contacted, (email) and the OP is waiting a reply.
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I did receive this reply on Tuesday of last week.
I am sorry for this issue, it is not a common issue and there are couple things that can cause this. What can we do to help make this right.


Adam Steffes
Quality Manager
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I responded right away with what would make me happy. A discount on the purchase of a case of their NEW ammo when it is back in stock. I've yet to get a reply so I emailed again this morning but they might be closed for Veterans day. I guess I'll give them another day then may have to give Adam a call. He did have his cell phone number in his signature.
 
I think I'd worry about their lack of quality control.... if they can't set the bullets right, why should I assume they do any better measuring out the powder, etc.
 
One question I would like to present is what is the manufacture of the cases and how much wear and tear is there on the rim of the cases with the setback.
Also if you have a set of calipers measure the outside of the case at the top and the one that is set back far enough measure the thickness of the case.
 
From the article:
"Armed with the common knowledge that .40 S&W cartridges are especially susceptible to pressure issues from bullet setback, and that the Glock 22 would blow up if you looked at it wrong..."​
Of course that's not correct but I guess the author thinks it sounds good and probably realizes that it paints those who might disagree with him in a negative light.

The truth is that although the .40S&W does tend to be more setback sensitive than some other calibers, the specific loading is a very important factor in how sensitive to setback the cartridge is. It's entirely possible that lighter bullet .40S&W loadings, especially if they employ a bulky powder, may not even allow the bullet to set back enough to be dangerous.

On the other hand, a heavy bullet .40S&W loading with room in the case to allow setback can achieve truly impressive pressures from just a little bit of setback.

So the author was fortunate enough to test some loadings that didn't blow his gun. That doesn't change the fact that SOME loadings can be dangerous if set back.

From the article:
"My experimentation and testing has shown to me that a lot of the common knowledge related to this topic is entirely wrong."​

No, that's what he THINKS his testing has shown him. The author made the critical mistake of taking some limited testing results and using them to form broadly sweeping conclusions.
 
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