CZ P07 Goes Ultra Kaboom With WWB Ammo

Hognose over at originally posted these dramatic images of the after effects of a CZ P07 explosion. His post was a brief analysis of a Reddit thread describing the poor CZ and the very lucky shooter. Visual evidence of the after effects of small arms destruction is always a solid reminder of the forces at work while shooting and fractions of an inch away from your fingers. .

If I had to guess, the kaboom appears to be the result of a double charged cartridge. After a little research, it seem that all CZ pistols offer sufficient chamber support, possibly negating any engineering deficiencies. The Winchester ammunition used by the shooter is from lot Q4172 (lot number undetermined at this point), however the ammo maker has yet to weigh in on the situation or analyze the damage.

Although it doesn’t appear to be a barrel obstruction failure, I’d still like to see down the muzzle end and, if possible, a picture of the recovered bullet.

I’m sure their are “Tupperware” critics out there right now, looking at these pictures and silently reinforcing their choices in steel framed pistols. So, what if this were an aluminum or steel framed gun? Would the damaged have been worse? Or would the metal have held strong and redirected the forces out the chamber and away from the shooters palm?

Maybe some materials engineers can chime in the comments section below.

CZ P07 Kaboom With Winchester Ammo Lot Number Q4172:

Cz p07 kaboom







I’d say be careful, but aside from weighing every round before you shoot it, there’s no way to know if there’s a double-charge hidling inside. And again, all of the above commentary is merely speculation at this point. Let’s wait for manufacturer input before drawing any conclusions.


LE – Science – OSINT.
On a mission to make all of my guns as quiet as possible.
Twitter: @gunboxready
Instagram: @tfb_pete


  • Tim

    Plastic guns. They’re tactical n’stuff.

  • TechnoTriticale

    The case seems to have an emboss around it at the top edge of the rupture. This could also be consistent with a discharge out of battery.

    • Vizzini

      That’s what it looks like to me. None of the photos make it easy to tell, but I don’t see any damage at all to the slide and barrel, which bolsters that hypothesis.

      • Pete – TFB Writer

        Would a double charge cycle to gun so fast, rupturing the case on the way to ejection, making it look like an OOB discharge?

        I would expect the bullet to still be lodged in the barrel for an OOB since most of the energy pushes out the case.

        • Phillip Cooper

          No. This is not a gas operated weapon.
          I’d expect a writer for TFB to know the difference.

          • Pete – TFB Writer

            Where did I say it was gas operated? That’s just silly.

          • Doctor Jelly

            I think his line of reasoning is along the lines of the double charge pushing the bullet down the barrel faster so the higher pressure then enters the gas tube and cycles the slide earlier than it should? My guess is he would be wrong anyway as with conventional recoil operation that the slide begins to unlock before a gas operated one would. But I don’t know myself, so don’t quote me internet…

          • Ed Forney

            What gas tube ?

          • Doctor Jelly

            There isn’t one. I was just working with Phillip’s line of thought.

          • Phillip Cooper

            Follow (or correct, please) my logic:
            Recoil-operated mechanisms such as this have timing calculated so that the bullet has (long since, in relative terms) left the barrel before the breech unlocks out of battery and the mechanism goes into OOB recoil. Once the bullet has left the barrel, in-barrel pressures immediately drop drastically. So I’m not seeing how the extra charge could equate to the OOB explosion in the rim of the shell.

            Gas-powered mechanisms use gas pressure for unlocking the bolt as well as recoil, so in that case, absolutely I would agree that a double charge would possibly create this sort of damage.

          • Pete – TFB Writer

            I’m tracking.

            My line of thought is based on the fact that there was an obvious and immediate failure. My initial observations lead me to believe that there was a double charge of powder inside the cartridge. (Other catastrophic failures in P07 pistols showed similar damage).

            However, since I wasn’t there, nor do we have a full scientific examination of the damage, I’m willing to accept that less obvious failures occurred.

            Partly why i wanted to see down the bore. Was there a squib that preceded the failure? I’d also like to see how the cartridge was positioned in the chamber. This the blow out in the three o’clock position or the four or five o’clock position? Are there cracks or damage to the chamber and/or barrel.

            Part of the problem of not having all the information about a failure and trying to draw conclusions is that sometimes you are left to ask about improbable scenarios.

            Hence, my question, is there anything that could have caused a double charge to appear as if it were an OOB failure.

          • Phillip Cooper

            Thanks, great discussion! I hope we find out what the issue was, as I use WWB for my practice ammo.

          • Tom of Toms

            Every 9mm load I’ve developed near or to max, using Auto-Comp and Unique, has filled the case nearly to the brim. My max Unique loads with a 115gr bullet are literally impossible to double charge. It would just overflow. Anyone know what powder Winchester uses in the white box line? If it is approx. W231 as is suggested all over the web, a compressed (either at press or in chamber due to setback)charge-and-a-half might unhinge a modern 9mm with ease.

          • Pete – TFB Writer

            Excellent. Thank you.

          • JoelC

            Unique is what I use for my max load and I fire it from a P07. A lot of people probably don’t know, but the rifling lands on the CZs (atleast the 2 I’ve messured) begin further back, which allows you to seat the bullets longer than spec. Makes me feel safer with that Unique load.

            I heard W231 is the winchester white box powder too. So yeah, may have even been a double charge but the rest of the powder just fell off.

            I would not be surprised to hear that this ammo was really handloads.

          • Sianmink

            The case is blown out where it’s unsupported at the feed ramp, and not really any forward of the groove. It blew out all the way back to the rim. If it had gone off OOB it would have blown out slightly further forward where the case was weaker, leaving the groove intact. It’s probably a double charge, possibly bad brass.

            (this is part of what I do for a living)

          • Pete – TFB Writer

            Thank you.

          • Paul Prochko

            Yes, possibly bad brass (would like to see the base of the cartridge case)… in high volume commercial reloading machinery operation…is it less likely a double charge than a hung powder charge released into the case… ?

          • Sianmink

            Most 9mm loads fill the case so it’s very difficult to impossible to double charge them. I suppose one could disassemble a wwb round and see if it is even a possibility.

          • Ebby123

            With an increase in powder charge, there is a corresponding increase in recoil and slide velocity.

            I’m not saying that’s the cause, but the end result would be similar between gas operated and tilting-barrel designs.

        • Vizzini

          Can go either way. I have had an OOB incident with a .22 rifle. Despite the case blowing out, there was enough power to force a .22 round down 20″ of barrel — the round didn’t get lodged in the barrel.

          ETA: in that case, I know for certain that it was an OOB, because it turned out much of the ammo in the box was out of spec and wouldn’t smoothly chamber in any .22LR chamber.

          • Pete – TFB Writer

            Wild. Makes me appreciate physics and ballistics going on under the hood even more.

        • Sianmink

          Maybe on a blowback pistol, but not a delayed. The physics just don’t work.

    • Joel

      That’s what I was thinking.

  • Alexandru Ianu

    If it’s a double charge, the gun seems to have held together pretty well.

  • Jim Slade

    Thank god the streamlight is OK.

  • tarnishedcopper

    Looking at the cartridge case, it appears as though it ruptured, venting the majority of the force out the side near the rim, causing the kaboom. I might expect that if it was a reload.(e.g. double charge, or cracked case) but not with factory ammo. Looks to me like Winchester is on the hook for this one, not that they will ante-up and admit it and perhaps recall other ammo from that lot. Had something similar to that 35 years or so ago with .22 LR Winchester purchased through DCM as a Jr. shooter. The cases were splitting in our Remington 513 T’s and blowing burning powder in our faces. No admission of a problem, or an apology, just a replacement of the case of ammo.

    • Pete – TFB Writer

      This was my analysis as well. Thanks.

  • AK™

    I always wonder how a Mark 23 handgun would handle a incident like this..

    • Vhyrus

      Better than the owner of the mark 23 after he realized his $2000 gun just blew up.

    • Jim Slade

      You might do more damage throwing a busted ’23, it’s so dam big.

  • Dougscamo

    There is another possibility though it would take a serious scientific examination of the wreckage….an undercharged case that caused a pressure spike….but who knows….all we can do is speculate….

  • Dougboffl

    Q4172 is not a lot number but actually the Winchester part number for 9mm, 115 grain, FMJ. Just pointing that out so folks don’t start freaking. Looks to me more like an OOB Kaboom. See the case deformation as pointed out by others. Note the debris/dirt & water marks on the gun/light – wondering if some crud got between breech face and primer to cause an early detonation or if the dirt/water is from dropping the gun after the Kaboom? Glade everyone is okay regardless.

    • Pete – TFB Writer

      Thanks for that. I’ll update the original post.

    • Dougscamo

      Think after a KABOOM like that dirt and debris would be on mine too….since I instinctively throw things that explode in my hand…..

  • Dickie

    Shoulda had a glock.

    • Jack Bissette

      ……yeah…..because with a Glock….it would have been substantially worse! …..with a slide in frame, the shooter had substantially more protection. …..I’ve seen plenty of Glocks come apart in my 26 year law enforcement carrer…..never seen anything like happen to a CZ!

    • Marlin

      I shot sme .45 reloads from my grandfather in law, out of my Glock 30 had a squib that did t allow me to chamber the next round… no powder or n the case. I found out where the missing powder went in a nice kaboom a few mags later. The double charged case was the last round in the magazine, which is probably why there wasn’t more damage to the gun, only had to replace the mag release, slide release, magazine and the trigger housing (where the ejector is) all in all it was $35 to fix, the magazine was by far the most expensive part. Case failed at the feed ramp, blown out in a very similar fashion to OP, I.believe that having more rounds in the magazine would have drastically increased the pressure the frame experienced, leading to a split frame as seen in the OP. As is was, there was brass slivers stuck more than halfway down the magazine well, which means the magazine was blown out immediately. The floor plate, follower, and spring were destroyed. The Glock 30 has seen a little under 500 rounds since replacing the parts and is functioning as flawless as ever.

      My point is that I think that rounds in the magazine can increase the pressure that the frame experiences during a kaboom, because if the barrel holds, then the only place for the gas to go is out of the mag well.

  • Vhyrus

    Not a materials engineer but mechanical engineer so I’ll comment. Based on the pics, aluminum probably would have fared as badly or maybe worse than the polymer. If you’ve ever seen someone take a hammer to an ar lower it shatters in a very visually similar manner. Steel probably would have done better since it has a much higher ultimate tensile strength and is capable of significant plastic deformation (bending and/or bulging) before breaking, although the chamber looks intact so I am not sure if the damage was the result of the case rupture itself or some sort of torque from the barrel on the frame caused by the explosion.

    • Pete – TFB Writer


    • Ed Forney

      Why would anyone take a hammer to an AR lower ? I have two, and they perform very well.

      • Glenn

        What AR lowers or hammers ?

        • Ed Forney


      • Vhyrus

        Theres a post or video online where a guy crushed an ar receiver and an ak receiver to show how much “stronger” an ak is over an ar. The ak receiver bent flat like a can but the ar receiver shattered. While this doesn’t really prove anything about ars or aks, it shows that steel will bend and deform long before it breaks while cast or machined aluminum simply cracks and shatters. Same thing would happen to an aluminum pistol frame vs a steel one.

        • int19h

          Now you got me curious. Would there be any benefit in making an AR lower & upper out of steel then?

          • Ed Forney

            An AR upper better be made of steel, or it would blow up on every shot !

          • Will P.

            Most all AR lower and upper recievers are made of aluminum. Basically your BCG, barrel, and small parts are the only steel on the gun.

          • Paladin

            AR uppers are made from aluminum, some are even made from polymer, and no, they don’t blow up on every shot because the bolt on an AR doesn’t lock into the receiver, it locks into a steel barrel extension. One of the key features of the AR15 design is that the receiver bears very little of the stresses of the firing cycle.

          • Ed Forney

            Have two, and didn’t know that.

          • Vhyrus

            Before I answer, I am not a firearms expert by any stretch, so this is merely my educated opinion.

            The short answer is no. The long answer is that, theoretically, you could use less material by utilizing stamped steel rather than cast or machined aluminum, but since steel weighs more than aluminum you probably would not save weight. I doubt an AR upper could be stamped efficiently due to it’s shape, but a lower almost certainly could. Technically, a steel AR would be more resistant to extreme abuse due to the higher strength and toughness of steel, but it would only matter in the most extreme cases, such as catastrophic failure or things like falling off a cliff or being run over by a tank. Steel can also be repaired much more easily than aluminum, so a broken gun could be welded or bent back into shape. It would also make it susceptible to rust though, so there’s that.

            If steel had any tangible benefit over aluminum, I promise you would see steel ARs for sale. Titanium, on the other hand… oh I better not get started on that, I just took a shower…

    • Kathy

      While I think a steel frame would have held up, I doubt the plastic or wood grip panels screwed to it would. I’d rather the frame blow out above where my hands are than direct the blast down to a weak point right underneath my grip…

  • Harry’s Holsters

    I’d like to see a pic of the shooter’s hand. I’m wonder if there was any damage beyond minor cuts and bruising.

    • DIR911911 .

      his underwear did not recover

      • Drew Coleman

        We should do a kickstarter to replace them.

      • Brick

        I guess this was a +pee round.

  • john huscio

    Looks like CZ couldn’t “improve on perfection”

    • Drew Coleman

      Stick a double charged round in a Glock and see if it suffers no ill effects.

      • john huscio

        Its more their recent crowing about moving into the polymer pistol market and being better than Glock. I’m well aware of Glock’s shortcomings

    • DonDrapersAcidTrip

      what does that have to do with this older hammer fired gun of cz’s

  • DIR911911 .

    this is why you put an extra pair of undies in the bottom of your range bag

  • Pete – TFB Writer

    No one noticed the obvious?

    Obviously the manual safety caused this kaboom

  • MrBrassporkchop

    So ++++++p++++++ in a cz is a no-go, got it.

    • Dougboffl

      It just needs some Gorilla glue & 3M ScotchBright pads to buff the repair before a quick coat of Krylon – done and done!

  • Cal S.

    Also a mechanical engineer here, and my thoughts are that a metal frame probably would have held up better. One only has to look at a picture of an M9 Beretta kaboom to see the difference. Would it still be usable? No. So it doesn’t really matter which, because the kaboom is handled by the metal parts anyhow. Buying a steel frame gun for the best chance at ‘surviving’ a 1/1,000,000 kaboom means you’re buying it for the wrong reason.

    If you’re that paranoid, just wear a solid set of range gloves and you’ll be safe from scratches.

    • Pete – TFB Writer

      Thank you.

    • Ebby123

      Lol. Spot on. Thank you for posting this.
      -Another BSME

      • Cal S.

        Yay! There are others out there! 😉

    • Sianmink

      I’ve never even seen a Glock frame fail like that. The blowout spreading down the side of the grip is troubling.

      • Cal S.

        It honestly just looks like cracking to me, I may be mistaken. The way the frame and slide interact may make all the difference.

        • Rap Scallion

          Looks like a tuna can the bears opened up!

  • Hoplopfheil

    That’s why you wear gloves, kids.

  • SilentMajority

    With a billion guns out there and trillions of rounds being fired off, its hard to say what exactly caused it, WITHOUT a BARREL view!

    • Pete – TFB Writer

      Yes. Absolutely this.

  • Joshua Knott

    eh dont buy whitebox i guess….. In regards to the polymer, CZ uses in frame steel inserts for the guide rails, and I believe their proof testing is pretty spot on, could have been alot worse.

  • esquire

    i had an xd 40 do the same thing. i believe it was caused by bullet set back from when the cartridge hit the feed ramp. this would cause excessive pressure and the noted damage. i think a double charge would have more of a hand grenade effect.

  • Michael Wilson

    A look at the various KABOOMs on the internet. I conclude that it doesn’t matter if you have a polymer frame, aluminum frame of steel frame gun. its going to blow your gun up in a way that renders it unusable and its going to hurt. Inspect your ammo before loading in magazines. Look for dents, cracks, deformations, feel the weight. If something looks funny, don’t load it. That is what I do.

  • Spencerhut

    Q4172 is the Winchester part number, not a lot number. People post so much without know a darn thing these days.

    • Pete – TFB Writer

      Corrected. Thanks.

  • Spencerhut

    Though it initially looks like an out of battery discharge more than a overcharge kaboom, an overcharge does create a very similar case rupture having seen a few in my life. I have this exact gun and getting it to fire even slightly out of battery has been impossible for me.
    The headstamp on the case and the condition of the barrel should tell you what happened fairly quickly.

  • Sianmink

    Okay I’ve never seen a glock go into 4 pieces before. How?

  • Doug Curtis

    This looks pretty obvious. My guess is he was rapid firing like a boss and had a premature hammer strike causing an out of battery discharge.

  • .45

    IIs it odd all I can focus on in that picture is “Wow, apparently they couldn’t find the trigger afterward”?

  • Mark Horning

    Without examining the firearm, it’s very hard to say of course. However,

    There is a pressure ring all around the base of the cartridge, in addition to where it blew out. To me that indicates an out of battery ignition, not an overpressure situation.

    • Doug Curtis

      My thoughts exactly.

  • YZAS

    Well, thats a little concerning. Anxious to see a final detemination.

  • 22winmag

    What’s a little double-charge between friends?

  • idahoguy101

    That ain’t good!

  • Paul Prochko

    Not sure what a photo of the recovered projectile would show (see article bullet comment) but I would like to see what the base of the fired cartridge case looks like. Looks more like out of battery but that’s cursory…No obvious barrel damage apparent in photos.

  • Jack_A_Lope

    Wait…CZs are made in Kansas City, KS? The things I don’t know, and I was just looking at the P07, too.

    • Andy Wolf

      The US Distro is in Kansas. They are still made in Czech Repub.

  • Dave

    What did they expect buying WWB? I’ve seen plenty of blown cases from them as well as dangerous pressure loads when on the range.

  • Andy Wolf

    *Insert antiquated, poorly-spelled, tired and uninformed Fudd comment about only owning steel-framed guns here*

  • Sam

    Isn’t it just as likely (or more so even than an overload situation) that this round was OK and that it was the previous round which was the problem: a squib, which left its bullet in the barrel? Shooter goes “bang, bang, bang, burp”, next trigger pull = no bang, says, “Huh?” shooter then racks the slide ejecting the squib case and chambering this round with the squib bullet still in the barrel, then touches off for a real BANG! Enough of a delay in pushing the squib bullet out with the next one (maybe) to massively spike pressure and push the case back out of battery enough to allow the rear of the case to rupture. (Something’s gotta give and it won’t be the steel barrel/chamber or slide if unsupported brass is available.) Would love to see the barrel and hear/know exactly the actual sequence of events, with no CYA’ing from the shooter.

  • John Redman

    If I were guessing, and I am, I would say that the cartridge was seated enough to allow the gun to fire but not seated enough for the action to properly lock. In looking at the spent casing it looks exactly like the casing from a 1911 that blew up in my hands. Luckily all the force was directed through the pistol grip and blew out through the bottom of the grip. The pistol, all steel, was destroyed but I came out, scared and bewildered, but otherwise unharmed.
    Just my two cents worth. The analysis of what went wrong came from the manufacturer who replaced the pistol at their cost.

  • Josh

    Double charge, OOB….. why not both? 😀

    Seriously, it was bound to happen to some poor bastard eventually.

  • Rap Scallion

    You were right on the first assumption…..that I am glad I have blued steel guns with wood stocks! I won’t outright crow about the, obvious to me, of the plight of the plastic guns, but if it quacks like a duck, and walks like a duck, then…..well then you know where this is going! Fact is that we don’t know what caused the failure, but there will proally be more explainations for it, than there were for the reasons Hillary lost!

  • BobValdez

    Considering the charge size, a double charge would be IMPOSSIBLE in such a short case. The picture of the cartridge case clearly shows it either fired out of battery, as the case was clearly not seated all the way into the chamber, OR, the case itself was faulty. A steel frame pistol might probably has just blown out the magazine, rather than the frame self-destructing.

  • Mac

    What caliber was it ? I don’t see a reference.