9mm Glock Barrel Support: Adequate or Not?

Whether a fan of Glock handguns or not, most agree that the Glock “KB” (“Ka Boom”) is a topic that is both enduring and widely-discussed on many firearm boards.  Glock detractors frequent speak of inadequate chamber support, flawed gun design allowing the pistol to be fired with the barrel slightly out of battery to skyrocketing pressures from shooting non-jacketed lead bullets through the factory barrel’s polygonal bore (which Glock does advise against).  Glock enthusiasts blame these KB’s on improperly loaded ammunition, defective factory cartridge cases if factory ammo was being used, and worn-out cases reloaded too many times if handloads were being fired.  Improper reloads mistakenly stoked with too much powder is frequently cited as a possible cause, too.  Who is right?

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Though not as much in 9mm, the widely-used Glock pistol does suffer from the stigma of blown cases in what is called Glock “KABOOM’s” or “KB’s”.  Is this something just inherent in the Glock design or might it be the product of other factors?

The first Glock KB’s that I personally witnessed were with a state-issued Glock 22.  Texas’ Department of Wildlife had recently issued them to the state’s game wardens, one of whom was a friend of mine. He fired a few shots using brand new factory .40 S&W 180-gr. JHP’s before he got a KB.  He was not hurt but the extractor left the gun as did the magazine. The case was still in the chamber and had blown along the extractor groove ahead of the rim.  His pistol was repaired in short order and within few days he took it back to the range with the same issue-ammunition…and with the same result, another KABOOM! Damage was about the same but he was losing his enthusiasm to fire his Glock 22, and I admit declining his invitation to shoot it as well!)

About this same time, a friend of mine bought one of the first 40-caliber Hi Powers to arrive at the local gun shop. He had not fired it but with a few days received a call from the gun shop owner advising him to call a specific number at Browning.  He did so and was asked to return the pistol for a free “upgrade” which had mistakenly not been performed on his brand-new Hi Power. Though it was like pulling teeth, he eventually learned that the Hi Power barrel was to be replaced with one that had been given a little bit more barrel support in the chamber due to possible KB’s with but one brand of factory ammunition: Federal.  This was the same brand being used by the game warden in his Glock 22.  (It should be noted here that I am both a fan and user of Federal ammunition and that the problem with their earliest initial runs of the then-new .40 S&W appears corrected long ago.  I have personally shot lots of it through many 40’s (Glocks and others) over the years with exactly zero problems.  I do not know if Glock has increased chamber support in their 40-caliber barrels or not.

Though I didn’t witness it, a friend of mine reported a KB in his Glock 21.  Neither he or nor I can blame it on the pistol.  Seems he mistakenly left a cleaning swab in the barrel.  Though a “low-pressure” cartridge compared to the .40, 9mm or .457 SIG, escaping gases around the trigger-area nearly severed his trigger finger.  (He checks barrels before firing now for some reason!)

I saw a minor Glock KB in 9mm while a police firearm instructor. The department was using “remanufactured ammunition” (commercially reloaded) from an obscure company because of the price.  I saw this 115-gr. ammunition blow and expel magazines from both a Glock 19 and a Beretta 92.  I had no problems with it in a Browning Hi Power but still refused to personally shoot or issue it for practice after that. It could be that the Browning just took the ammunition in stride or more likely, I happened not to get one of the company’s inadvertent overloads by pure luck or chance!  It is possible for brand new factory ammunition as well as factory reloaded rounds to be out of spec.

I thought that it might be worth the time and effort to compare the Glock 9mm barrel with other factory barrels and see if anything can be deduced. (I understand that 9mm is not the primary caliber in which Glock KB’s are being reported, but 9mm is the only caliber in which my Glocks are chambered, so it will have to do, at least for this initial report.)

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On the left is a brand new Glock 19 barrel and on the right is a used Browning Mk III barrel.  Both have a Corbon factory 9mm round dropped in their chambers.  It appears to me that the Glock barrel actually has slightly more support than does the Hi Power barrel…and the Hi Power is not “notorious” for blowing cases. Whether it does or not, cases in the Glock barrel are not excessively unsupported.

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On the left is an unfired extra STAR Model 28 barrel.  It appears to have less case support than does the Glock 19 barrel at the right.  (I have shot more than a few hot rounds through my STAR Model 28 pistols.  None of the fired cases exhibited any signs of pending blowouts or case separations. This visual comparison also favors the Glock barrel.

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The Taurus PT92 (left) and Glock 19 (right) appear to offer very similar case support based just on visual inspection.

I do not know if the same is true with other calibers, but it appears that at least in 9mm, the Glock offers case support comparable to other 9mm handgun manufacturers.  FWIW, chamber case support appears the same in my mid-90’s G17 as well as two more recent G19’s. (There are very few autoloaders from any manufacturer which offer full or complete case support.  The reason is that some support must be sacrificed for reliability and this has been safely done nearly from the beginning of autoloading handguns!

It is widely reported that Glock chamber dimensions are “generous” in the pursuit of reliability. People report that handloaded ammo which chambers reliably in their Glock factory barrels sometimes does not in aftermarket ones having match-grade dimensions. I do not own any match barrels for my Glocks but do for the Browning Hi Power.  Let’s see what happens if we drop a fired case from a Glock 17 into a factory Browning Hi Power barrel and then repeat using a Bar-Sto match-grade Hi Power barrel. If the Glock chamber is substantially larger than the Hi Power’s, the fired case will not fit in it.

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This Federal 9mm cartridge was fired in a mid-90’s vintage Glock 17 pistol. The case dropped into the factory Hi Power barrel without problem. It appears that the factory Hi Power chamber and that for the Glock are about the same size. A light tap with my trigger finger seated it fully. Vigorously shaking the barrel dislodged the fired case.

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The same is NOT true for the Bar-Sto match Hi Power barrel. Heavy thumb pressure on the case was necessary to fully “chamber” it in this barrel. Removal required a cleaning rod down the barrel to bump it out.  The picture shows the case as it was dropped into the chamber and before fully “chambering” it with thumb pressure. The match-grade barrel does have tighter dimensions that either the factory Glock or Hi Power barrels. This was expected.  The same thing happens if trying to seat cases fired in a factory Hi Power barrel in the Bar-Sto without resizing first.

So what is causing the never-ending saga of Glock KB’s?  I see several potential causes, some which could work independently and some which would work in tandem with others.  Let’s take a look at possible contributing factors for this phenomenon.

·         Sheer numbers: Glock pistols are so prolific world-wide that the number KB;s or related mishaps would appear high even if this percentage is less or no greater than those for other less-frequently used pistols. 1% of 1,000,000 is a greater number than 1% of 10 though both represent the same percentage.


·         Different calibers than 9mm have less case support: Because I do not own non-9mm Glocks I don’t have the guns to check.  For those who do, the very simple approach used in this report might be one way to see if this is true or not. It is neither complicated nor difficult to do.


·         Is it possible that a few Glock pistols have left the factory with improperly heat-treated barrels and or slides? I have absolutely no indication that this has happened but have seen a slide breech face failure on a brand new Glock 19.  It was NOT caused by dry-firing (though I strongly doubt that to be a real cause of any similar failures, anyway) because the gun was new, i.e., it had just come from the gun shop and its owner was not a shooting enthusiast. Obviously, the slide should never have left the factory…but it did.  Is it barely possible that something similar might result in a KB? Could it be that due to sheer numbers, “Glock Perfection” just isn’t as universal as might be desired?


Here is the cracked breech face on the new G19previously discussed.  This was not caused by dry-firing as is sometimes (wrongly) claimed. (It seems reasonable to expect any fractures caused by dry-firing to be around striker opening, doesn’t it? Something would really have to be out of whack for the striker spring to provide enough force to crack steel.  It just does not ring true to me and I do not believe it.)  The pistol had not been dry-fired!  This happened while shooting standard pressure factory ammunition though no KB occurred. Note how the circular fracture in the steel appears to outline where a 9x19mm case would be during firing.  The point is that something was wrong with the steel alloy or heat treatment, etc.  This slide got out of the factory and was a lemon.  Could not something similar be causing KB’s…or at least contributing to their numbers?

·         Can Glocks firing with the slide very slightly rearward and the barrel out of battery cause KB’s? I think that it is possible though not so much in 9mm.  Yes, the striker can still pop the primer with the slide rearward a few thousandths of an inch but unless firing a double-charged cartridge or something similar, I just don’t think that the case is retracted enough more for it to blow.  That said, perhaps it is possible in other calibers that may have less case support. I flat do not know. This could be checked using this article’s approach by someone owning forty-caliber handguns, including a Glock. I tried to drop the hammer/striker on three different make 9mm handguns beside Glock with the slide slightly retracted so that the barrel was at least partially unlocked; it can be done. Glocks are not the only handguns in which this can be done. If case support is approximately the same, so should results be, i.e., very, very few reported KB’s.


·         Can new factory ammo or that which is remanufactured be mistakenly loaded to excessive pressures? Though rare, I do believe it can happen. I have seen factory-loaded ammunition from the Big Three that had defects such as primers seated upside down or not even present, bullets seated upside down, partially-crushed cases, to no powder being present at all.  I believe that it is unusual but possible.  Most of us will remember seeing the occasional ammo recall from one company or another and in some instances, “excessive pressure” was the reason cited. A reloader can make a mistake and so can commercial manufacturers.


·         Maybe the polymer/plastic frames do not hold up nearly as well as steel in the event of a KB? I believe that to be likely but have seen no articles or studies on it. It seems reasonable.


·         Could the shooting of lead bullets though the factory polygonal barrels, despite Glock’s warnings not to do so, contribute to KB’s? Possibly, but I have no idea how many shots would be required as that would at least be related to the hardness/softness of the lead alloy being used as well as the powder being used and the charge weight. This brings up another possibility: mistakes at the reloading bench.


·         Might it be possible that some barrels w/o proper case support at the rear of the chamber inadvertently left the factory? Only the company will know for sure. From The Complete Glock Reference Guide (Third Edition)” by PTOOMA Productions, Page 25, we read that some early G17 chambers were incorrectly drilled “out of line”. If this could occur, might not at least some barrels lacking proper case support have made it onto the market?

It is my observation that chambered cartridges in 9mm Glocks are not routinely under-supported. If they were, might not the proof loads that each reportedly test-fires before leaving the factory cause KB’s?  Perhaps we might not hear about them, but I wager the company would make the necessary chamber-support changes to end it.

In 9mm, I do not believe one is any more likely to suffer a KB with the Glock than if using another maker’s pistol. Perhaps the same is true in other calibers but not having the pistols to check; I cannot say and leave that work to be done by other interested parties.


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