The Case Failure FAQ

version 2.4, 21 April 98
by Peter Jordan
[the views expressed herein do not necessarily reflect those of .40something or The Glock Papers]


You Say kB! and I Say Case Failure

Dean Speir, well-known gun magazine writer, has coined this general phenomenon, "kB!", which stands for kaBoom! I'll just refer to it as a "case failure" in this article, since the case is initially ruptured, which in turn can cause damage to the pistol and the shooter.

The weakest part of a pistol is the cartridge case. When a case fails, the escaping ignited powder causes the pistol to have a catastrophic event in the form of possibly blowing out the magazine, and/or damaging the pistol. The shooter and those around him/her are also at risk from flying pieces.

Long before Glocks were created, case failures were occurring. One reason Glocks are in the limelight so much today is simply because there are so many of them out there.

All pistols are subject to the case failure problem, not just Glocks. Even Glock 9mm guns are subject to it. Any documented evidence regarding case failures is welcome. Just stating something on the "net" is not good enough. Nowadays, a lot of these so-called statements of catastrophic events are based on urban myths from third hand rumors, and just downright "brand name" bashing. Give a lie a 24-hour head start, and it becomes immortal. Just the documented facts please.

There are a number of reasons for a pistol to have a catastrophic failure, such as pulling the trigger when the barrel is clogged, over-charged cartridge, under-charged cartridge, weak brass, over-crimping, over-seating, poor pistol maintenance, using poor quality bullets and/or other components, etc. The one common ground of these problems is usually the case failure

One key link to this common ground of the case failure, is that in the vast majority of these catastrophic events, reloaded ammo was being used. Yes, a very small minority of case failures with factory ammo has also occurred. Factory employees are only human after all. The fact remains that Continuous Improvement Programs and Quality Control in companies is much more controllable and measurable than with private reloaders. I reload and believe the quality of my work is excellent; but my equipment and reloading style may be very different than others who may do better or worse than me.

About Lead

I have successfully used hard lead bullets (Oregon Trail) in a Glock, although I don't like to use lead. It's messy to work with and the bullet lube smokes a lot during shooting and raw lead is more toxic, especially at an indoor range. Coated Precision Lead Bullets don't smoke but can stain your barrel so cleaning it is more difficult.

The main reason I don't like to use lead is that it does not have that bounce-back quality, like jacketed bullets do. In other words, if you squeeze a lead bullet, it will stay squeezed as if it had no memory of what its previous shape was. Because of this, lead bullets have more of a chance of slipping into the case during the forceful feeding cycle stage of a semiauto, especially if there is a misfeed. Example:

I once had a feeding jam. The slide was moving forward at full force in an attempt to seat a lead bullet cartridge in the chamber. I did a tap and the round seated. The pistol went into full battery. I fired it. The perceived recoil was much stronger than normal. I picked up the brass right away to examine it. A caliper measurement showed that the case had expanded 2/1000" more than normal, AND, it actually had crease marks where it bulged in the unsupported chamber area. Thank goodness it was new strong brass and it held together. That means during the forceful feed and tap stage, the bullet had slipped into the case, causing an over-seating event. And this cartridge had passed the thumb pressure test before shooting it!!! --- the bullet was solidly in place.

Thus, using lead in autopistols is more dangerous In My Humble Opinion. If there is a feed jam, at least rack the slide so you don't use that particular bullet. Long winded, but that's what I believe unless someone can prove me wrong.

Regarding Out-Of-Battery

No one has proven that the standard factory Glock design has a problem of firing out-of-battery, period! Glock has made a number of important enhancements, especially beginning in 1992, to improve their design. In fact, the latest .40's coming off the production line have a stronger frame to take advantage of the Glock engineering effort which designed the new .357 Glocks (a 9mm Magnum cartridge). If Glocks had a glaring defect in the marketplace today, competing pistol manufacturers would bury Glock Incorporated in an instant, but they can't! Rumors, urban folklore, and theories don't count.

If the Glock design were defective, than ALL semi-auto pistols would be defective and we would ALL have to go back to using revolvers. Every auto pistol I've ever shot can fire slightly out of battery, but not enough to matter because it operates within known engineered tolerance specifications. As the Glock slide starts moving rearward, the barrel starts dropping almost immediately --- That's not very much folks. Guess what! Check out your favorite S&W, Colt, Beretta, Desert Eagle, etc. They will all fire just slightly out-of-battery. The amount of the out-of-battery condition depends on several factors: pistol design, condition of the pistol, and the kind of ammo being used, etc. And that's why the most accurate testing of the out-of-battery condition should be performed with live ammo in a qualified lab environment. Simulating the out-of-battery condition with an empty pistol by just pulling the slide back a little bit and pulling the trigger, does not bring all the necessary variables into play, although, it can give you a *rough* idea of how your pistol is functioning.

Glocks have gone through some of the most strenuous tests and still kept ticking afterwards. One of the more recent thorough tests was performed by the FBI, which was very well documented in the 1998 Autopistol magazine (Harris Publications) and the 1998 Glock Annual magazine. Believe me, if there was an out-of-battery problem and/or Glock design flaw during the 120,000 round torture test, the FBI would not have declared the Glock models 22 & 23 the overwhelming winners. As a result, the G22 and G23 are now authorized to be issued to FBI agents. This information is just a little teeny weenie bit more substantial than the urban myths that continue to be propagated from misinformed people who "spout off" about Glocks without anything to really back up their interpretations.

The simple fact of the matter is that most all of the Glock problems today are caused by case failures induced by reloaders, and by a very small amount of bad factory ammo, as well as by not maintaining the Glock pistols as originally designed.

There are a good many Glocks out there. So, you'll keep hearing a lot about them. You have a choice of staying with the hard facts, or, listening to the outrageous, Glock-bashing approach by the misinformed rumor mill.

I did see a very interesting situation at the shooting range, where a shooter racked the slide and let his hand ride the slide forward, which of course hampered it. The Glock 23 was slightly out-of-battery as a result. He pulled the trigger and heard a click. He waited for awhile and then looked at his Glock to confirm it was ever so slightly out-of-battery. He ejected the brass and it had an off center strike. The strike was not strong enough to ignite the primer --- that's very good. I put the round back in the pistol and it fired fine in full battery. I shot several other rounds to see if the G23 was functioning OK. It was.

As I watched this same shooter more closely, I noticed he also placed his right thumb high on the slide as he was racking it with the pinch (sling shot) method. This guy had really big hands. After he consciously started releasing the slide cleanly and kept his thumb out of the way, his G23 started working perfectly.

Later, I tried using the sling shot racking method (not recommended), with my right thumb pressing against the slide, to simulate what I had seen at the shooting range as mentioned above. I was only successful part of the time of inducing an out-of-battery state, and that's when I wasn't cleanly letting go of the slide during the racking cycle. I believe the thumb contributed to the problem, but was not the sole reason for the above shooter's out of battery experience.

I know of one seasoned firearms instructor who said that he recommends for most shooters, to place the thumb lightly against the slide. In class, he has seen the thumb interfere with the slide, but it is very uncommon, and usually occurs by those with large hands that naturally have a very strong grip.

I've heard some people state that build-up in a dirty chamber can cause a round to not seat completely, and therefore may cause an out-of-battery situation. I wouldn't know about this since I always keep my guns clean. Heads up: With the new .357 bottlenecked cartridge, you must be very careful to actually clean the INITIAL wide part of the chamber. One way to do it, is to use a .40 caliber bore brush to clean ONLY the wide part of the chamber. Then, use the 9mm bore brush to clean the rest. Just don't get carried away and ram the .40 caliber brush all the way through the bore!

After the new subcompact G26/27 models had been out for awhile, I happened to be perusing at a gun show. I decided to buy an aftermarket double recoil spring system for $45.00, to replace my standard Glock 23 guide rode and recoil system. At the time I was very excited about getting a double recoil spring that would emulate the excellent Glock 27 recoil system.

When I got home, I quickly assembled my new aftermarket double recoil system into my Glock 23. I racked the slide. It seemed to work fine. I then decided to dry fire it. As I started to pull the trigger to take up the initial slack, I noticed the ENTIRE slide moved back so it was just slightly out of battery. I blinked my eyes a couple times and then pulled the trigger again. Same thing.

Bottom line: I happened to buy an aftermarket double recoil system that was quite dangerous; it successfully put my G23 into a very slightly out-of-battery condition every time I pulled the trigger! All kinds of things about this product started entering my mind like, where's the Quality Control, and was it manufactured in somebody's garage during their spare time, etc? I humbly reinstalled my standard Glock recoil system and realized that Glock engineering was pretty darn good after all. Whenever you buy a part for your Glock, make sure it has been checked out and approved by a qualified Glock armorer.

I cannot help but wonder how many people may blame their Glock for not going into battery, for off center primer strikes, etc, when it is actually "User Induced Error". I'm of course not saying that Glock has never produced a lemon off of their production line either, although the above mentioned events hopefully makes one think a little.

On the other hand, The "unsupported chamber in the 6 o'clock position AND the loose chamber combination" such as in the Glock .40's, is a potential problem, but much more so for reloaders. This combination is more susceptible to case failures. Some people have also reported off center primer strikes, although a number of variables can cause this. Luckily, I believe there is a solution.

Set Up for Why a High Quality After-Market Barrel is a Good Idea

Since the Glock .40's demonstrate my point so well, I'll use them as an example. I'm not trying to pick on the .40. In fact, I like shooting the .40 Glocks best of all, even though the G30 is a close second. I'm very excited about getting my new medium longslide Glock 35, in both .357 and .40, in April '98.

I'm not saying Glocks are unsafe if you are shooting well tested factory ammo and you use the common sense to keep your Glock in good working order. I'm concerned about those who reload with Glock .40 barrels, for those that shoot hot factory ammo, and for those that shoot regular factory ammo who just want the "added insurance" of even greater safeguards.

Checking the Brass From Different Barrels as a Proof Point

Shoot a few factory rounds through a Glock .40 pistol using the Glock barrel. Save the brass. And then shoot a few rounds through the same Glock pistol using an aftermarket Jarvis barrel and then separate the Jarvis shot brass from the earlier Glock brass.

Next, use calipers to measure the diameter of the lower part of the .40 brass. What you will consistently find is that the brass from the Glock barrel expands the brass to a diameter of .432 or so. The brass from the Jarvis barrel expands the brass to .427. New factory brass measures about .422 or so. This means that the Glock .40 barrel expands the diameter of the brass twice as much as a Jarvis barrel. And that's the problem. And that's why you should not reload with brass fired from a Glock .40 barrel. And once again, that's why you so often hear the name Glock, because of an amazing high number of Glock .40's on the market in proportion to other companies, who can only dream of having the numbers that Glock has.

Interestingly enough, the new .357 Glock barrels do not over stress the brass at all. These new .357 Glock barrels expand the brass to a nice mellow .427 - .428, even with full power loads, which is good enough for reloaders to reuse the brass, and it adds an extra level of insurance to those who shoot factory ammo. As I recall from my Sig P229 experience, I believe its brass usually expanded to around .428 - .429. So Glock engineers really did it "right" with the help of a bottlenecked cartridge. Thank you!

I've never heard of a Glock blowing up using a high quality aftermarket barrel; To do it, you'd have to have a poorly maintained/abused Glock that is malfunctioning, and/or to create a huge overcharge and/or use weak brass, that would be a reloader/factory error, and a very painful one at that.

Regarding a Fully Supported Chamber:

A "tighter chamber with a fully supported chamber in the 6 o'clock position", like the new .357 Glocks, is the best combination of all. A "loose chamber AND unsupported chamber in the 6 o'clock position", like the current .40 Glocks, is the worst combination of all. A "slightly tighter chamber with an unsupported chamber in the 6 o'clock position" does work, as you'll see in the next paragraph. A "loose chamber with a fully supported chamber in the 6 o'clock position" seems to work OK for the HK USP40, although the brass is still over stressed. It's the combination of "loose chamber AND unsupported chamber" that is the least effective, especially for reloaders.

My Accumatch .40 barrel has an unsupported chamber that is basically the same as a Glock .40 barrel, exposing just as much brass casing in the 6 o'clock position. But, and very importantly, the chamber is slightly tighter, more in line with other companies like Sig-Sauer. As a result, the brass is not brutalized by being over-expanded and even "rippling" back to cause the infamous case bulge in the 6 o'clock chamber opening area.

This is an important point--> My Accumatch barrel expands the .40 brass to a normal .427 with zero case bulge in the 6 o'clock position, even though it has a huge unsupported chamber just like the Glock --- the only difference is the slightly tighter chamber, which successfully contains the pressures during the firing sequence without over stressing the brass.

My Accumatch barrel feeds just as reliably as the standard Glock barrel. So all this talk about Glocks needing a super loose chamber for reliability is nonsense.

With a slightly tighter chamber, the round actually seats itself more efficiently than if the chamber is too loose, and I'm not exactly sure why. I'll go out on a limb and guess that the slightly tighter chamber causes the cartridge to feed more consistently at the exact same angle without banging around as it might in a loose chamber. From my humble experience using a good third party aftermarket barrel in a Glock, I have never witnessed an off center primer strike or an out-of battery problem . Inquiring minds would like to know why.

A good aftermarket barrel will not stop all case failures from occurring, because all guns are subject to this problem based on a number of variables. An aftermarket barrel is beneficial for those that reload and/or shoot hot factory ammo, and, serves as added insurance for those that just shoot plain ol' factory ammo.

Aftermarket barrels that I have successfully used in Glock models were made by Jarvis, Bar-Sto, and Accumatch (now Advanced Tactical Firearms). I had some bad luck with early model Olympic Arms barrels, although I have been told, but have not personally verified, that Olympic Arms has worked out the bugs in their 357 Sig barrels.

I have not tested other calibers as thoroughly as the .40/.357 Glocks. So someone else interested in these other calibers can do it and let us know the results.


These are suggestions only, and cannot be taken as absolute proof. If you just shoot factory ammo through your Glock, you have a good chance of never having a problem, especially if you are using well tested factory brands. If you reload, get a good after-market barrel that has a slightly tighter chamber, and then you will have a good chance of never having a problem, as long as your reloading quality control department does a good job!

For Reloaders

  1. Review reloading practices once a year to refresh your mind of good safety tips and to assure that you continue to maintain safe step by step procedures.
  2. Always examine your brass before reusing it.
  3. Keep track of your brass and throw it away when it is showing signs of fatigue or if you just aren't sure about it. Don't be like the old timers that just keep shooting their .45 brass until it cracks.
  4. Use new brass for full power loads.
  5. Don't use brass if you don't know its history. Practice safe brass.
  6. Remember, the brass is the weakest part of your pistol!
  7. Get in the habit of using calipers and case gauges to help you reload within specs.

For Everybody

Learn how to correctly clean and lube your Glock, and do it on a regular basis. If you are licensed to carry a Glock in a concealed manner, you MUST carry a clean pistol for legal reasons, as well as for making sure it is in good working order.

  1. Let a Glock armorer do a complete disassembly maintenance check of your pistol once a year.
  2. Learn how to perform the Glock safety checks, to make sure your pistol continues to function according to specifications. A good time to do these checks is while you are cleaning your pistol --- better safe than sorry.
  3. Constantly review safe gun handling procedures as taught by qualified firearms instructors, and take a safety course if you never have. Unless you're Perfect, you must keep reviewing your gun handling techniques to stay on top of it, not under it.

Be safe and have fun.



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