CZ Go kB!

Pistols are supposed to go bang, but not like this:

The owner and shooter are alright, but as you can see, this gun is a write-off. Closer look, with the casing laid on top:

The pistol is a polymer-framed CZ P-07. CZ-USA has, from examining the pictures, put the blame on the ammunition (Winchester white box ball, lot number Q4172). Winchester has yet to weigh in.

The lot number of the detonated case is Q4172. Another lot that has been reported to produce a kB! is K7190.

Facts and pictures from this thread at Reddit. More pictures after the jump.

Some parts and accessories may have survived, but the pistol’s frame is destroyed.

The destroyed polymer frame is not the full extent of the damage. The ambidextrous safety’s right side lever has been blasted off.

Lucky that there was no injury, really.

From the left, the destroyed gun still looks OK!

It will be interesting to follow the thread and see if Winchester steps up and helps the poor fellow replace his destroyed CZ, or if they have some argument that something else caused this gun to turn low-order grenade on the firing line.

41 thoughts on “CZ Go kB!

    1. Haxo Angmark

      guns should be fired as infrequently as possible. That way they will explode less often.

      IOTW, dry-fire practice is much less expensive, and the gun will not explode.

    1. Hognose Post author

      It’s hard to tell because of the photo (cell phone?) with a narrow depth of field and auto-focus on the plastic frame. Looks like it may be which is consistent with the blown out case. the fundamental reasons for a blow-out like this are out of battery ignition, obstructed barrel, or overcharged/wrongly charged round. The shooter claims the barrel was not obstructed, the CZ is well protected against dropping the hammer before the slide is fully in battery with the barrel locked up to the slide, and that makes the overcharge the most probable cause. Without examining the gun.

  1. John Smith

    Well, damn. I occasionally buy Winchester white box stuff for training. I then dump it in ammo boxes for ease of use at the range. The lot numbers are absolutely lost to me.

  2. DB

    The only time I’ve ever had multiple dead primers in a box of factory ammo has been Winchester white box. Notified Winchester, with the box lot number. Their response was to demand that I ship the entire box to them, at my expense. That is, their response was to flip me off. As you might imagine, it can’t be on sale enough for me.

    1. ev

      Same issue here, I had one box with multiple primer failures. I refuse to buy Winchester training ammo now, and I’m hesitant to try their SD loads too.

  3. Dave smith

    Ammo leave behind in the Nam dirty tricks division of the spook forces. Out in the Ashau valley we 0311’s would often find suspicious caches of AK ammo and pistol rounds that looked too inviting. Theses never seemed to have been left by Nguyen. Years ago had a bunch of Chinese import 22 ammo that blew up a really nice Hammerli pistol. Reloading my own center fire ammo for title one stuff makes sense.

    1. Hognose Post author

      It takes a certain personality to be an effective reloader. Some people do not have the single-minded focus necessary.

      There were several programs in Vietnam (mostly in Laos and Cambodia, actually) to provide Charles with “enhanced” small arms ammunition. POLE BEAN and ITALIAN GREEN were a couple of the project names at SOG. It was actually a psychological operation meant to shake the enemy’s faith in his weapons and cause disputes between the PAVN and its arms suppliers. No later US use of such items has been declassified.

      It’s documented that the USSR and Germany did this to each other in World War II as well.

      A variant of the blowing-the-enemy-up with bad ammo trick is telling your own troops not to fire enemy ammunition because your clandestine services have tainted the enemy supply — which gets back to him and makes him double and triple check all his ammo. Whether you did it or not.

      1. LSWCHP

        I’m happy to say I’m out on the autistic part of the spectrum that actually enjoys reloading and applies the necesssary degree of concentration and caution required for dealing with energetic materials. I’ve loaded probably 100000+ rounds of ammo over the years and nary a problem, and I simply couldn’t have afforded to buy that amount of factory ammo.

        I do have a few less focussed mates though, who have blown up tubes of primers in the press, which is an unhappy experience, or loaded hundreds of rounds with no powder etc etc.

  4. John

    I worked in the repair dept. at a gun manufacturer. I have seen this from every major manufacturer of ammo. That said, it is usually handloads that cause “traumatic disassembly” All said and done it doesent happen often with the “big 3”. When it did they usually made good on the repair. The only time I can remember that the repair was refused , was with a lot of ammo loaded for the govt. (.45 cal.) that was not supposed to be sold to the public.

    1. cm smith

      “The only time I can remember that the repair was refused , was with a lot of ammo loaded for the govt. (.45 cal.) that was not supposed to be sold to the public.”

      Was that perhaps the Winchester +P truncated cone .45 that supposedly flunked the underwater depth test for the Navy? A local distributor had cases of that. I bought 2-3 boxes, but never shot any of it.

  5. Simon

    I think i read that the Brits reloaded K98 ammo with explosives and dropped them behind the lines.

  6. Hillbilly

    This is one reason I use loads that come as close to 100 % capacity as possible and/or bulky powders.
    Powders like Bullseye which are economical to shoot are and flow through a powder measure easily so fine grained it is easy to get a double charge.
    What works best for me is to do it in stages, I very seldom sit down and do the whole routine at once.

    1. Dyspeptic Gunsmith

      Yep. This, oh, so much this.

      With Bullseye and some other fine-grained powders, it is possible to nearly triple-charge a .45 ACP case.

  7. Keith

    For those of you with the knowledge would a metal framed pistol like a 92FS, HP or 1911 done that? Or would the metal frame have contained the explosion?

    1. Ned2

      This happened to my 92. Bent the trigger bar lug, but that was the extent of the damage. I was using cheap plinkers, so I’m not sure if a heavier load would have caused more damage.
      The Usual Suspects were in concensus this was just a too hot load from the factory. I wondered if it could have also been a weakened case?

      (Ammo was Ultramax-remanufactured)

    2. Dyspeptic Gunsmith

      Depends on the level of over-pressure. 1911’s have absolutely ka-boomed. There are several failure modes in a 1911 to a case head separation:

      1. Barrel hood blows upwards/outwards in the ejection port.
      2. This continues longitudinally down the barrel, resulting in the slide splitting lengthwise, starting from the ejection port and working forward.
      3. If there’s still an overpressure situation, or the case head separated predominately on the lower half of the case (which used to be the dominate mode of case failure in 1911’s with “unsupported” chambers), the side panels of the grip blow off or splinter to vent the pressure. Shooters then say “ouch.”

      Then we get into the other, more extreme, failures. But the majority of failures I’ve seen follow the above modes in a 1911.

      1. Tim, '80s Mech Guy

        Saw one like that years ago, Wyoming Arms sort of 1911 in 10mm. Split all the way down the barrel. Bulged the slide on the ejection port side, did not vent downward it all went out towards 2 o’clock. Factory PMC ammo, 200gn ball I think.

  8. Paul

    Shooting prairie dogs I have had a lot of case separations from all three big ammo makers , only Winchester stepped up to replace all the fired brass and provided a prepaid shipping method for the return of the bad brass. They also shipped me a ton of extra ammo for the trouble. I would be very surprised if they do not do the right thing.

  9. Hartley

    Interesting – that gun appears to be set up to run with a silencer, but it isn’t on it now. Wonder if that was any factor?

  10. Brian


    Brief story and question. You mentioned that “the CZ is well protected against dropping the hammer before the slide is fully in battery with the barrel locked up to the slide”

    I had an experience with some commercial reman 9mm ammo in my P 07 that was a bit unnerving. Click, no bang. Unable to rack slide. Cautious inspection showed that the pistol was not in battery. Apparently the bullet was lodged tightly in the barrel, which prevented the action from being opened.

    The external hammer had fallen, but the firing pin did not hit the primer.

    When I got home from the range I checked the entire lot of ammo and found that it was all slightly out of spec and over-long. Took it all out of rotation.

    I am VERY glad that the pin didn’t hit the primer as I expect I would have had a kaboom like the one above.

    My question is, what mechanism prevents that firing pin from hitting the primer when the P 07 is out of battery? How does it work? Did I get lucky, or is this a feature built into the design of the pistol?



    1. Hognose Post author

      It’s built into the gun on all CZ pistols (SA/DA) although it may be a little different on Omega trigger pistols than earlier ones.

      Several mechanisms provide safety on the CZ.
      1. If the trigger is not pulled back, the hammer can fall only into one of the cock (full- and half- ) notches, depending on how far back it is. (Decocker equipped CZs drop to half cock, not fully down).
      2. The sear mechanism is blocked from releasing out of battery by position of the drawbar, which can’t engage unless it’s in a notch in the slide. That sounds hard to understand so I’ll try to post a picture or two.
      3. The DA trigger is designed so that as it wears, it increases the engagement between drawbar and sear. When it finally fails, it fails safe — rather than going too early, it won’t go at all. (Which a gunsmith can fix, if you ever get to that point).
      4. The B model and up (including all the P-0x) have a positive firing pin safety. The pre-B is still about 99% drop-safe because it has a rebounding firing pin that is shorter than the space between the hammer face and breech face, so it only has its own inertial mass if dropped, insufficient to fire a cartridge.

      These safety features are not unusual in modern auto pistols, they’re done differently by different manufacturers but they’re pretty much industry standard.

      Another interesting problem much like yours.

      1. TRX

        A damaged, out-of-spec, corroded, or otherwise stuck firing pin could also cause an out of battery ignition.

    2. Hillbilly

      On the CZ forum there is a lot of talk of shorter than normal chambers. They recommend a plunk test any time you change up ammo.
      Even some factory rounds are supposedly loaded long enough to engage the rifling upon chambering.
      I know for a fact my Beretta will take a Hornady XTP loaded to a longer OAL then my P09.

  11. Hognose Post author

    Here’s how a CZ disengages, illustrated with a pair of screenshots from the American Gunsmithing Institute’s CZ assembly / disassembly video. Gun is a CZ-75B.

    Upper picture: slide retracted. The drawbar (visible through the forward cutaway) is cammed down out of engagement with the sear by the slide rail.

    Lower picture: slide forward. The drawbar rises into the notch in the slide rail. You can just see the wire spring that raises it, underneath the drawbar. This notch is timed so that it the drawbar can not come up before the slide and barrel are fully locked together.

    1. Brian

      Thanks for the detailed explanation.

      As Hillbilly noted above, I’ve found some discussion on the forums about the way the CZ pistol chambers are cut. They do appear to be “shorter” than some other pistol manufacturers and less tolerant of ammo that is loaded out of spec. I haven’t had any difficulty with new ammunition. Just this one batch of reloads.

      Thanks for taking the time. Very much appreciate the work you put into the blog.

  12. 11B-Mailclerk

    Third picture: The bulge at the base appears to ring the entire cartridge. This would be out-of-battery ignition. If it was only bulged at the unsupported part of the feed ramp, that would instead suggest an over-pressure event.

    The CZ mechanism would prevent an out-of-battery event under normal circumstances, but what if:
    a) there was a high primer activated by breech face pressure?
    b) the firing pin was stuck in the forward position?

    I have seen blown cases much like this from fixed-pin SMGs, and some near-kaboom badly ring-bulged cases from said SMGs.

    I haven’t personally observed a high-primer kaboom (at least one proven to be from a primer) but I have heard of such things.

    it does not take much to stick a pin forward, once. A little machining debris, or a whole lot of fouling can do it. This would be my bet here, if that case is truly ring-bulged.

      1. Tim, '80s Mech Guy

        I’d put my money on out of battery too, that was my first instinct on seeing that pic of the case.

    1. TRX

      Oh, yeah. I have a milk jug full of “.380 belted Magnum brass”. Some brass is soft enough at the base to deform when my M11A1 is in rock-n-roll made. Every session I find a handful with the side of the case blown out.

      Technically there’s probably something wrong with the gun, but it doesn’t affect reliability at all, and there’s so much commotion coming out of the ejection port the only indication is the mutilated brass.

      Feh. Open bolt SMG, it’s not exactly a precision firearm…

  13. Texas dude

    It happens? Shooting has some inherent hazards. Wear eye pro, know stuff and drive on.

    Having been present for maybe millions of rounds of ammo fired, stuff goes wrong.

    1. Duty load from a major manufacturer; in about 100K rounds of pistol ammo, we had six squibs. I personally had one. Luckily everyone paid enough attention that nobody blew any pistols up. Manufacturer (as most will) replaced all of the duty ammo we had left (30K? its been awhile) with new stuff. They also inspected and shot the rest, and found no issues. I guess we already got all of the bad ones.

    2. New production M855 from the military; keyholed in several carbines. Nothing blown up, but still troubling.

    3. Major manufacturer ammo last month. Possible squib blew up a can and the barrel on a major manufacturer upper. Stuff happens.

    4. Anything I loaded when I was a teenager. In the days before cheap internet ammo, it paid to have friend’s relative with a progressive reloader, an FFL and who would sell you components at cost. Pistol stuff was fine. Rifle…my QC was awful. Never blew anything up, but left my teenage years with the understanding that I should just pay more and buy factory.

    If you shoot enough, odd things happen. We have also had lots of blown primers lately with center fire rifle ammo, from a major domestic manufacturer, and the ammo was stored in gentle, almost lover-like conditions. And fired through major manufacturer carbines in good repair. Who knows? Stuff happens. It is nice to know the why and how, but wear eye pro, and expect that every few years or so, weird stuff is going to happen, and at about twice that interval, something is going to go BOOM! Have spares and move on.

    1. 11B-Mailclerk

      “Blown primer” = backed out of the pocket? If so, that is a -low- pressure sign and/or possibly one of excessive headspace.

      In most cases, the primer will back out under the initial pressure, then the case recoils and re-seats the primer. If the pressure is very low, there is insufficient force to re-sear the primer, and it is partially blown out.

      In the case of excessive headspace, there is more room, and the primer moves further, possibly all the way out. This can happen low pressure or high.

      If the “blown primer” is -pierced- your firing pin may be too pointy and or too long. (or wrong primer – pistol in rifle)


  14. Mr. K

    To me(I’m no expert) it looks like it fired out of battery. The only reason I say this is something similar happened to me firing a GSG-522. The rifle attempted to double feed and the second round jamming into the first caused the round to fire out of battery causing the round to bulge out with a ring around the part of the case that didn’t fully seat into battery and the pressure causing an explosion out the side of the casing facing the ejection port. It looked almost identical to the way the case looks in the picture. Scared the $&!7 out of me but I was ok and the rifle after carful inspection was not harmed. Case in point, lesson learned, the GSG-522 is not a real MP5 don’t try to shoot it as such! LOL

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