Earth-Shattering ka-Boom! How (and Why) Guns Explode

Just yesterday Scott at Kentucky Ballistics posted a very sobering video detailing his Serbu RN-50 quite literally exploding in his face. A lot of people have asked if I have seen it, and I figured this is a good opportunity to discuss the different ways in which guns can explode, and what some manufacturers have historically done to fail-safe their designs.

While not nearly as cool as Scott’s “Just Put a Thumb in it” shirts, I do have a pretty nice lightweight Carhartt shirt now available in the Forgotten Weapons merch store!

Scott’s video on the event:


  1. You’re really doing a great job
    keep up the good work!
    I find all your videos fascinating.
    I thought I knew a lot about firearms in the 60 + years that I’ve been reading and listening to people.
    After seeing your videos; I realize I don’t know a 10th of the knowledge base

  2. Question for you guys who know this stuff. What is the relative strength between a threaded locking system ( as is shown in the exploding gun video) and a lug locking system? Also would a gas venting safety aka the Arisaka(as shown in McCollums video) made a difference?

    • “What is the relative strength between a threaded locking system and a lug locking system?”

      A. There’s no one categorical answer. It would depend on calculating the locking area of the threads vs. the locking area of the lugs.

      B. Keep in mind as well that even a lug locking system is locked (barrel into the receiver) by threads too.

      “Also would a gas venting safety aka the Arisaka(as shown in McCollums video) made a difference?”

      Not really in this case. Scott was hit by pieces of the breech mechanism, as opposed to mis-vented gas.

      • “Also would a gas venting safety…”
        Yes, overpressure venting is a standard feature on all sporting or hunting firearms. That is your, shall I say “life wheel”. When you have the opportunity, take a look. Even my Savage .22cal rifle has it. There is no justification to circumvent/ omit safety features. I would not fire a rifle without it.

        • A firearm is a type of pressurized fluid system (like steam or firemain), and the breech serves the function of a valve. Every effective valve has rigid structural components (body + cutoff mechanism such as a gate or ball), and a gasket, which is pliable but relatively weak. The cartridge casing serves the gasket function; it is a more effective seal than the rigid receiver and breech cap, but is not structurally capable of holding full pressure without them.

          The term “overpressure venting” is misleading. The vent does not, like a relief valve, release pressurized fluid on the high-pressure side to prevent structural failure. It exists (as Ian said) to provide a safe path of least resistance, AFTER “gasket” failure. Being on the low-pressure side downstream of the “valve”, it cannot possibly prevent catastrophic structural failure as seen in the video.

          • I am referring to purposely drilled hole into locking area of receiver. This will allow for the excessive pressure in case of casing rupture to escape harmlessly sideways.

          • I understand exactly what you meant. It was already clear from Ian’s video.

            What I don’t understand is why you refer to “overpressure” or “excessive pressure”, seemingly implying that the vents serve a function similar to relief valves (venting from inside a pressure vessel to reduce the risk of breaching the vessel), when their function is actually similar to flange shielding (deflecting hot gases in a safe direction AFTER they leak outside the pressure vessel), which does not really pertain to the video.

          • No excessive pressure, no need for relief. It is playing with words. We both know what it means.

          • No connection to the inside of the pressure chamber = no way to relieve pressure. If you superimposed a wire diagram of an Arisaka or a Gras over the RN-50, their vents would be in the dead air space next to or right behind the Serbu’s hammer.

            In fairness, the firing pin hole right in the middle of the breech cap (which cannot possibly be gas-tight, and points right at the shooter’s face) could be faulted for that very reason – but that isn’t (and has nothing to do with) the failure that Scott actually experienced.

    • “Threaded in” has stronger support than “ threaded out”… This fellow uses a threaded out breech block…

      • Diameter of the threaded inner part would be much less. How could it be more strong with less support metal?

        • Diameter where cup or plug threaded is your choice… Choose it freely… Treaded on has no support at outside and threaded in has a solid support outside…

      • As I recall from M.Serbu’s video it is an externally mounted, manually removable cap. The proportion/ length of thread look generous. I’d say simple, efficient design overall.

    • “…would a gas venting safety aka the Arisaka(as shown in McCollums video) made a difference?”

      It potentially could have for the specific weapon but not for the reason they were typically used in bolt actions (which is to prevent hot gas and powder from blinding the user). A YouTuber, Backyard Ballistics, pointed out in a video that, due to the female screw cap breach design, a case failure could alow gas to put pressure over the full inner surface area of the cap, not just the contact area of the case. (If you have 60’000 psi exerting force on 2 square inches instead of .5, you get 120,000 lb-force instead of 30,000 lb-force). If a case failure was the ultimate cause, gas venting near the breach face might have prevented the cap from shearing off.

      • Backyard Ballistics is not your average YouTuber, he is a profesional ballistic forensic expert from Italy.

    • Stephen, I wonder if rather than it being just a question about strength of threads perhaps, gasses escaping the case briefly expanded the threaded cap meaning the threads had less overlap to resist the high rearward thrust?
      This could mean the system could be very strong until a case ruptured.

  3. “Extra-extra hot”… what kind of terminology is it? What does it mean? Handloaded without regard to recommended values? Anything is possible, I suppose.

    Next item I notice: “very-very old”… ah here we are onto something. By extended period of time the powder tends to (especially if subject to movement/ shaking or to severe temperature changes) to become finer. That may alter pressure curve.

    From what I gathered thru my employment in industry is that there has to be somethin GROSLY off in order to get breech explosion. I recall one such event when straightness gauge was left by mistake in the barrel. Also reading thru the years about various accidents it typically points to irresponsible experimentation with “extra-hot” loading. Any such event is HIGHLY unlikely to happen with factory ammunition.

    And finally – do not expect the gun barrels to be built with high coefficient of safety. They are typically made to around 1.5 and that should be plenty (under normal circumstances of course). Steel is elastic material to some degree. Every gun on its way out of factory is tested with an overpressure round pertaining to particular standard. If all done as it supposed to, not much risk to shooter is present.

    • Squibbed guns are just as likely to rupture than regular guns fed extremely over-charged cartridges. It gets worse if someone squibs a field gun (ARTILLERY) with lots of mud and a bundle of grenades… I could be wrong.

    • I have known people who reload their ammunition. As matter of fact a friend of mine does just that. Knowing his pedantic approach I know I can trust his reloaded ammunition at any time. So it comes down to knowing what you are doing and be consistent with it.

  4. Do you have any documentation of the Colt 1900 actually failing and causing injury. Thanks

  5. Does Ian still have the piece of scrap Neil when a gun exploded on him a couple of years ago?

    Everyone be safe and sane – and please shoot safely.

  6. That story about 300 blackout in .223 guns reminds me a lot of the many and varied but always serious admonitions I’ve heard from older shooters about the dangers of bringing 12 and 16 or 20 bore rounds to the range together and the dire results of mixing them up. I’ve never seen it happen, thankfully, but sure as Hell it’s something that I triple check every time

    • That’s the reason 20 gauge cartridge case plastic “hulls” are moulded in yellow, and 12 gauge and 16 gauge are not. It’s to call attention to the 20-gauge round, as in “do not load into 12-gauge or 16-gauge chamber”.

      Similarly, .38 Super ACP cartridge cases are traditionally nickel-plated, to remind owners of older .38 ACP pistols not to use same. And yes, you’d be surprised at how many pre-Super Colt and other brand .38 Automatic-chambered pistols are still “out there”.



    • I have inspected a .300B bullet removed from the barrel of a C-8 (AR type) 5.56 rifle. Longest, skinniest .22 bullet I’ve ever seen.
      In the event of a catastrophic case failure in an AR type rifle, the case will rupture in the area of the chamfer in the chamber mouth, and gas will be vented. This is by design. As Ian mentioned, the upper will be damaged. The magazine may be blown out. But the shooter will probably not be harmed.

      • That is exactly what happened to me. Shooting military surplus 5.56fired a few rounds, everything was working fine , then BOOM, RIFLE BLEW UP. Upper destroyed, bolt and carrier destroyed, magazine blown out of magwell with great force with remaining rounds blown straight down from magazine hitting concrete with some of them flattened. Barrel, lower receiver and stock were fine.
        I was pretty shaken, but luckily not a scratch.

      • There is actually whole niche (researched) of guns designed to shoot oversized bullets, to get crazy amount of pressure and speed, so called squeeze bore.

        • Karl Puff and Hermann Gerlich first made it practical in the 1930s;

          Both sides experimented with it during WW2 to get maximum velocity out of a tungsten-core penetrator in an anti-tank gun. The “squeeze-bore” generated striking velocities so high that steel shot shattered on impact.

          The Wehrmacht actually had two “squeeze-bore” AT guns in service, the 2.8cm SchweresPanzerBusche 41 (SPzB41) with an “emergent caliber” of 21mm, and the 7.5cm PaK 41 with one of 5cm. Both lasted until the 1943 Fuhrerbefehl restricting tungsten supplies to the manufacture of machine tools.

          In the end the Allies, after experimenting with the “Littlejohn adaptor” on 37mm and 2-pounder (40mm) tank and AT guns, found that the Armour-Piercing Composite Rigid (APCR) shot with a tungsten core got the same results at close range (under 300m), and the Armour-Piecing Discarding Sabot (APDS) tungsten shot did so at all ranges. Neither one required a ‘squeeze-bore” to work properly.

          The modern-day Armor-Piecing Fin-Stabilized Discarding Sabot (APFSDS) “silver bullet” or “arrow” tank-gun round is the direct descendant of the APDS.



          • “(…)Wehrmacht actually had two “squeeze-bore” AT guns in service, the 2.8cm SchweresPanzerBusche 41 (SPzB41) with an “emergent caliber” of 21mm, and the 7.5cm PaK 41 with one of 5cm.”
            There also existed 4,2 cm leichte Panzerabwehrkanone 41 although only few hundreds were made in total. It has final caliber 28 mm.

  7. In about 50 years of shooting, I’ve had one squib load. It was a factory (I won’t name the company but their boxes were green) .38 special round and the bullet got stuck in the barrel of my Smith J-frame. I weighed the other rounds from that box of 50 and found one to be significantly undercharged and another had no powder at all. I bought the ammunition when those green box guys were going into bankruptcy and I suspect that the interest in quality control just wasn’t there. Thankfully I was just plinking – or “practicing”- and heard and felt the difference with that bad round. I didn’t try to fire again and saved the pistol and maybe a couple of fingers.

    • Good story. I have read similar one before. It is not a good idea to consider ammo’s quality as given. Especially with the older vintage.

  8. Excellent video. I would love to see more content like this. If you are willing to share, I would also like to hear more about the specifics of your experience that led to the making of the “dangerous things are dangerous video.” It was a great lesson on the need for medical training and know-how in such situations. What exactly happened etc.
    Thanks for all you do.

  9. Out of battery discharge about 30 years ago with a low brass plastic 12 ga field load in an 870. Case ruptured, lifter snapped in two across the middle,powder grains sprayed down through the receiver and into my forearm, where they stayed for 10 years or so before working their way out (or in?). Still have the broken lifter and mangled case as a reminder that Murphy is always in the building.

  10. Isn’t there another mode of failure – where sabotaged rounds are left for an enemy to find. Loaded with explosive rather than propellant?

    • James in Oz – Yes. I’ve heard stories of the German Army removing the delay (a length of fuse) from a grenade, so that the knob and string was directly connected to the detonator, then leaving it behind when they retreated. They counterattack, Ivan sees a handy grenade, pulls the knob and BOOM. In Vietnam Project ELDEST SON involved LRRP’s and snake eaters from SOG infiltrating NLF and PAVN ammunition dumps and substituting grossly overcharged ammunition. Just a few rounds, but enough to cause distrust among the troops

      • “(…)removing the delay (a length of fuse) from a grenade, so that the knob and string was directly connected to the detonator, then leaving it behind when they retreated.”
        There existed 1-second delay Brennzunder for Eihandgranate 39, see 2nd image from top
        Thus causing unexpected explosion for anyone assuming it has default 4,5-second delay.

        • A “field expedient” with the standard Brz39 (blue pull-bead) was to unscrew the friction igniter set, remove the delay fuze, and insert the end of the igniter directly into the gain. Leave it lying around for an inquisitive enemy, and boom.

          The 1-second delay (red pull-bead) was intended for use in setting boobytraps, with a tripwire or etc. attached to the igniter. The delay was to allow the “booby” and friends if any to get within the grenade’s blast/fragmentation radius before it detonated.

          See; Grenades and Mortars, Ian Hogg, 1971.



          • eon, Thanks, that’s where I heard of the German practice. Ian Hogg’s works were both informative and a pleasure to read. This book was part of a whole series, originally published in Britain, called in the States “Ballantine’s Ilustrated History of the Violent Century”. Now, given the format, about 100 pages, if I remember, you won’t get much detail – the phrase “a muile wide and an inch deep” comes to mind – but in the late sixties-early seventies nothing else was as available and affordable. Still, they serve as good introductions to their subjects and provide an idea of where you might wat to dig deeper


            And a chechklist


            Happy reading!

          • Col. B.;

            I have about every one of those books. In fact, I have two copies of several, the originals (especially I.H.’s) having become so dog-eared from constant reference.

            They are overviews, to be sure, but I.H.’s The Guns 1914-18 and Grenades and Mortars are still today the only really detailed technical treatises on those two otherwise largely-ignored subjects.



          • In the US, the NSA maintains a list of code names. They are random and designed to give no indication of what they refer to. This even applies in peace time, I can remember a big, mULti-service exercise at Yakima, called CABER WARRIOR. Figure that one out

            Back in the Fifties, Britain had its “Rainbow Codes” like Orange William – an AT Weaapon, Blue Water – a SSM, Blue Boar – a nuclear bomb, Blue Steel – a stand off missile. Blue Parrot – a radar, Blue Circle – “sardonic name for concrete ballast for Buccaneer while awaiting Blue Parrot radar. Also used for Sea Harrier ballast in place of Blue Fox radar, and Tornado F.2 ballast. From the Blue Circle cement company.”


            You can spend hours looking up some fascinating projects. For example,

            Green Mace – 5-inch rapid firing anti-aircraft gun (96 60 pound rounds per minute!)


            Thankfully for the British taxpayer, most were terminated relative early

          • According to
            Operations in which large numbers of men may lose their lives ought not to be described by code-words which imply a boastful and overconfident sentiment, such as ’Triumphant,’ or, conversely, which are calculated to invest the plan with an air of despondency, such as… ‘Massacre,’” Churchill wrote. “Intelligent thought will readily supply an unlimited number of well-sounding names which do not suggest the character of the operation or disparage it in any way and do not enable some widow or mother to say that her son was killed in an operation called ‘Bunnyhug’ or ‘Ballyhoo.’
            As for British rainbow codes, they even begin for nuclear-tipped anti-ship missile they assigned name GREEN CHEESE

      • Very useful reminder. Thanks.
        High explosives produce shock wave velocity 10x as high as propellants. It is almost magical.

  11. I’d imagine Scott and his friends and acquaintances have examined the hell out of the barrel, but absent a conclusive report from them, is it possible there /was/ enough of an obstruction to cause an overpressure failure — in the form of one of the SLAP sabots? I’ve heard tell that they were known to cause problems in service, separating in the barrel.

  12. 1) What is the procedure the manufacturers (weapon and ammo) and the BATF take to investigate incidents like this

    2) APIT is still manufactured in 50 Cal BMG

    3) Lesson from my college days, “Know your dealer and avoid bad dope”. Shooting rounds of unknown provenance – even if they are cheap (and WHY are they cheap, one askes) is risky

    4) Surplus rounds from certain countries are dangerous. For example, Turkish surplus has as reputation of having been loaded hot.

    5) Explosives change their characteristics over time. A brand new round maybe be perfectly safe. A fifty year old one, who knows…..

    6) Bottom line, do your research and err on the safe side

    • “What is the procedure the manufacturers (weapon and ammo) and the BATF take to investigate incidents like this”(С)

      There is no procedure for such cases.
      I will say more, in the US the manufacturer is not responsible for such “accidents”.
      At most, you can demand a free replacement for a defective product…
      For the same. LOL
      Well, or demand a return of money.
      Separately, you can try compensation for damage to health.
      But this, first, will have to be proved in court…

    • Origins of ammo – very good point. And it can get tricky.

      I been shooting Chinese surplus made in 1970, in 3 different rifles. It is remarkably accurate (considering its military destination) and reliable ammo. On the other hand I read of case when someone shot same caliber ammo in his SKS made by S&B (which is considered a benchmark by some) and he had a ruptured case. So you tell me what to make out of it.

  13. There is only one reason.
    Illiterate design.
    All these garage-built “rifles” have never been credible.
    And what happened is an excellent confirmation.
    Of course, you can think deeply about the “tragic coincidence” …
    But I will say – an organic design defect. Therefore, the result is predictable and even expected.
    The whole question was if the godfather would come across a hot enough (old) cartridge with a rather tired (old) brass.
    When brass cracks in a properly designed weapon, the gases are vented to the sides and do not cause serious harm.
    In this case, the gases were under the cover and, acting on a twice as large area, tore off the thread.

    • I don’t even know if Scott should be condolently or congratulate him better.
      Probably I congratulate you from the bottom of my heart.
      He actually “almost bit the dust.”

      • Did you see Serbu’s videos? His shop looks like large garage with CNC machines in it. Yes, he is very knowledgeable, but even that may not be enough to avoid accidental fluke. Look what happened to P.Mauser – and he was Mr.Somebody.

      • In this case we should be also looking at ammo as possible culprit. Unless we know more about origin of it, it is hard to make a definite statement.

    • I have seen couple of M. Serbu’s videos. He calls himself “gun designer – gun nut”. That’s fine by me. But, but, but – no one is perfect and everything in engineering has to be double and triple checked – and tested remotely on range, in adverse conditions. IF (and I do not know for sure) he missed a safety feature (such as emergency pressure vent) it can be a serous strike against his operation. I hope I am wrong in this case.

      • Part of the problem may be the computers give an illusion of exact results.THe concept of significant figures seems to be forgotten or not even known.

        My dad was an engineer back in slipstick days and his philosophy on critical components was to design the item, add a safety factor, then double it. May have cost more, but none of the pressure vessels he designed ever blew up.

        • The computing automated technology is a guide or AID as they like to call it. At the end everything has to be practically tested in often absurd conditions.

          You dad obviously had a healthy respect for reality and as you say, it paid out for him. People work based on experience of others and own intuition. It gradually turns into their own and they become masters of trade.

          • I think you are very right here, “practical test in absurd conditions” is what lacked, and most likely designer, who is, based on his videos, very cad competent, put all his trust in computing and math, not seeing some other perspectives that can happen.

  14. It doesn’t matter at which specific address the production is located.
    The following is important
    (as my great-grandmother used to say)
    “When a person has been building toilets all his life, if you give him all the necessary resources to build a palace, he will build a big, bright and shiny …
    TOILET. “(C)

  15. I know nothing about gun making but it occurred to me that the breech block is screwed over the end of the chamber like a bottle cap. Would it have made any difference if the breech block was screwed into the back of the rifle like a plug.

    • Heavy artillery pieces using bagged charges traditionally have interrupted-screw breeches that work in the second manner. The theory is that as the gas pressure of the propellant burning is exerted on the “head” of the breech block, the outward pressure of the breechblock’s “elastic” metal threaded section on the standing breech will be increased, always to a greater level of PSI because of relative surface area.

      So theoretically the pressure holding the breech “plug” in place will always be greater than the pressure in the chamber.

      Also, the “inside-threaded” breech with that “elastic” breech face is perfectly safe with bagged charges, as it creates obturation by radial expansion; measured in micrometers, to be sure, but it’s there.

      By comparison, the outside thread “screw breech” generally requires a metal cartridge case for obturation, as with the Whitworth field gun of the 1860s. It also generally cannot tolerate pressures as high as the inside-threaded breech, as the breech end of the barrel can “bulge” more easily under pressure.



      • Look up Debange obturator for bag guns. Elasticity for obturation at the breech end occurs courtesy a flexible neoprene or fiber seal compressed by the mushroom head. Gun Chief, C/1/103rd FA

  16. This was a great presentation of a very interesting subject. Thank you. I always get uneasy when I see someone shooting experimental ammo or playing around with making slugs out of strange materials, and I usually pass by those videos.

  17. I eventually saw Ian’s introduction video, and I want to say, I am delighted by it. This is he best way presented in common language, how things around firearms work. This lecture is well beyond reproach – a masterpiece.

  18. In 2006 I was working out of FOB Chapman in Afghanistan. We had a lot of old weapons in our little stash, among them a Long Branch No. 4 built (IIRC) in 1943. It had a peculiar bulge in the barrel that was visible about half way to the muzzle. Externally the rifle looked normal, but the bulge could be seen when one examined the bore. I’m curious bout what might have caused that without blowing up the gun.

    • Several things could cause it. The most obvious is somebody firing a live round with a piece of cleaning wad cloth stuck in the bore at that point. Yes, the wad will be pushed out by the bullet, but there will be a pressure spike where the bullet met the wad in the bore.

      The other, going back to WW1, was the firing of “rod” type rifle grenades with blank ammunition;

      This was the earliest type of rifle grenade, and was first invented by Mr. Hale of the Cotton Powder Company;

      The rifles used to fire such “rodded” grenades inevitably developed “bulges” in the barrel at the point where the end of the “rod” was when the blank cartridge was fired.

      The only real solution was a rod exactly the same length as the distance from the muzzle to the front of the bulletless blank cartridge, i.e. extending clear to the leade’ of the bore.

      The “Manen Hale” rodded grenades used in 7 x 57 Mausers by the Mexican Army in the fighting in and around Mexico City during the “Ten Tragic Days” (9 to 19 Feb 1913) in the Mexican revolution had just this type of rod. incidentally, they improvised blank round for grenade launching by removing the bullets from standard service rounds, adding more powder (two risky procedures) and then shoving the mouth of the cartridge neck-deep into a bar of soap to create the “gas seal” (not exactly safe either).

      When the British Army first issued Hale rifle grenades in 1914-15, the first lots were actually originally built for the Mexican army, with rods sized for the 29.1 in (74cm) barrel of the Mexican 7 x 57 Model 1910 Mauser. The rods were accordingly “cut” to the shorter (25.1 in/64cm) barrel length of the SMLE No 1 MK III, but this did nothing about the problem of a roughly .271 in diameter rod in an 0.303 in bore. Bore erosion was thus another problem, even without the added factors of priming and Flanders mud and wet.

      A Long Branch made No. 4 with such a bulge, in Afghanistan, could have been used to fire “improvised” rodded grenades courtesy of the Darra Adam Khel manufactories, but that’s just a guess.



  19. It doesn’t matter how sophisticated the calculation methods are. This is not a Martian rocket, everything you need can be calculated in a couple of hours on a piece of paper, and you don’t even need a calculator.
    But none of the most advanced technique will help if such calculations are not considered necessary or if the calculation scheme is simply incorrect.
    I suspect that in this case, the calculation for the abnormal operation of brass was simply ignored.
    Laziness or a banal lack of experience is a separate issue.
    But everything that happened is a direct consequence of the negligence admitted by the designer.

    I checked.
    This thread can withstand working (and test) pressure quite well.
    But as soon as the brass is shot through, the load on the thread jumps to 2-4 (depending on the steel) above the limit.

    • And yes.
      This is not a coincidence.
      Take a live cartridge and cut the brass so that it would shoot through.
      And you will get a similar, consistently repeatable result.

      Perhaps this can be cured by adding ventilation ports.
      If they don’t loosen the lid so much that it rips off along the line of the holes …

      • I don’t think vent holes would save this design and prevent injury,
        main culprit is that its basicly a pipe bomb in front of shooters face, supported additionally by only these 2 small “lugs” that actually sheared off to became lethal shrapnels.
        If it was encased in some kind of thickwalled receiver that would catch the threaded cap, it would be, maybe not so nifty for quick reload, but much (or at least somewhat) safer.
        Also, by this pivot design, on video its seen that breech end jumped up, and thats why cap hit him in the eye instead directly to the mouth.
        After that, barrel literally did a somersault across the table, its almost comical.

        My bet is that designer never did a destruction test, believeing all is foolproof, because if he did, he would have seen how the rifle behaves and what parts fail so miserably.

        But lastly – all the buyers see what it is, how it functiones, even a (joke) name signals fairly crude contraption, so they take the risk willingly.

        • The holes help very well.
          If they exist and their area is sufficient.
          For this cartridge, you will need a hole so large that it can loosen the “bolt” too much. And that will turn the rifle into a “right-hander only”.

          The longer I look at this device, the less advantages the author has.
          Such a deliberately crude and primitive decision.
          Despite the fact that 200 years ago there were many designs that were no more complicated than the one presented, comparable in simplicity and manufacturability. And they had much better user properties.

          In general, it resembles the trend followed by many current manufacturers led by Kel-Tec.
          They seem to say with their whole appearance, “Look what a simple and primitive design. Obviously, you can’t come up with anything more reliable or cheaper.”
          But in fact, it is not simpler or more reliable, but it is exactly a turnover.

          • To be honest, first time I saw the rifle I was surprised of somebody even trying going off so simple, crude route with .50cal, and surprised even more, that it apparently worked with no issues.
            But we have a saying here: a cup is going for the water until it breaks…

  20. And then there is the M9 (berretta 92) slides hitting shooters in the face.

    Oops, forget I brought that up.

    • Slide cracking around the locking lugs and eventual slide breakage is endemic to the Walther-style locking system that the M9 inherited from the P.38 by way of the M951. there’s a reason nobody else has ever used it.

      It’s just fine with WW2 German-standard loads intended for the P.08 (124-gr @ 1,050). With anything more emphatic, look out.

      The only real cure is a full-coverage slide to give added strength, as on the Llama M92 version and the Lyttleton M88 clone made in South Africa.

      Of course, not making sustained use of IMI “Uzi Carbine” level loads sort of helps, too. But don’t tell the SEALs I said that, OK?



  21. Two things. There is a Murphy’s Law variation that said’s ” It is impossible to make anything Fool Proof, since Fools are so Ingenious ” . And I saw a story and photo of a Musket in a Museum that was used in the Civil War buy a Union soldier that had a Barrel busted. He had fired the Musket just as a Confederate soldier across the battle had fired his Musket. The Confederate’s Musket Ball in a One in a Million chance came across and went into and down Union’s Soldier’s Musket’s Barrel. Causing the Barrel to explode ! the photo showed the barrel with both Balls in it at two places.

    • Kinda reminds me of when I was a kid, I was goofing around in my yard, throwing the darts in long distance at an angle to see how they fly and land. Suddenly I saw dart hitting something in the air – it lodged itself in telephone cable that was strewn across yard. I suppose If someone gave me tens of thousands of darts and whole week to just throw, I would not be able to hit it in a way that it lodges in, especially from that distance I was casually throwing.

  22. So much of this is insuring a load is appropriate for a particular firearm. In 1982 I blew up an M19 Smith using a handload my friend had put together for a Ruger Blackhawk. The load was fine for the heavy Blackhawk, but but too much for the lightweight Smith. I’ve been a very conservative handloader in the 40 years since.

  23. If my experience blowing up the Model 19 serves as an example, this guy will have a bad case of the flinches for about the next six months, maybe more. Except for a few tiny flakes of metal that cut my hand, that experience did not injure me. It may take a long time for the shooter to get over this one.

    • “In the summer of 1918, a group of soldiers of the 301st Tank Brigade, which I commanded, was having 37mm. gun practice which I was observing. One defective round exploded in the muzzle, wounding two or three men. The next round exploded in the breech, blowing the head off the gunner. The men were reluctant to fire the next round, so it was incumbent on me, as the senior officer present, to do so -in fact, I fired three rounds without incident. This restored the confidence of the men in the weapon.

      I must admit that I have never in my life been more reluctant to pull a trigger.”

      George S. Patton, “War As I Knew It”. From the chapter entitled “Earning my pay”.

  24. If I was firing a slug rifle of that design, I think I’d glance down the bore BEFORE loading a round. Every time.

    Come to that, I’d make it standard drill with any type of single-shot rifle that gives you a look down the bore as handily as that. My grandfather’s High Wall comes to mind. My brother still shoots it off the bench, and sometimes bags his muley with it. I think I’m going to ask him if he doesn’t check for light at the end of the tunnel.

    If he says no, I’ll send him that horrendous .50 cal YouTube.

    • In this case, neither looking into the barrel nor the correct storage of ammunition will help you.
      Longitudinal cracks in brass are found in all manufacturers, although this happens much more often on old brass.
      This rifle is structurally programmed to explode with cracked brass.

    • I have a few shorter than a cartridge pieces of rod in various diameters. They are easily used to check for bore obstructions when dropped down the barrel- no bolt removal required.

  25. Ammo storage is almost as important as load and other safety factors.

    The Army has an entire career field among DA civilians called QASAS or Quality Assurance Specialist (Ammunition Surveillance). These guys spend their entire careers chasing down the various stupidities that the troops get up to, along with those of the contractors who produce the ammo in the first place. You’d be shocked at the sorts of idiocies people get up to, in the face of extensive training to the contrary.

    One of the things I remember quite well was talking to one of our guys from Fort Lewis that I ran into over in Kuwait. He was not having a lot of fun, because there was lots and lots of stuff for him to do, cleaning up after the 2003 invasion and all the rest of that. One of the issues we specifically discussed was the spate of “‘splody” rifles that people were complaining about up on the range complex that they were using to get everyone prepped for going north. Whole thing got traced to one lot of ammo out of a container that turned out to have been misdirected into the “frustrated cargo” (meaning that it was essentially “lost” in the system) and which had spent close to five or six years sitting in the desert sun of Kuwait. When they finally got around to clearing it out of the frustrated cargo yard, it was sent off to the ammo depot where it somehow evaded everyone’s attention, and the ammo contained within it got issued out rather than being extensively tested. One lot of ammo from that container turned out to have been susceptible to temperature-induced chemical changes to its propellant, and instead of doing the usual nice, slow deflagration… It essentially detonated, producing a much higher and faster pressure curve than it was supposed to. Everything else in the container? No real issues–It was just that one lot of ammo. Identical specification ammo from a different lot with a different propellant didn’t have any safety-related issues, but that one lot…? BOOM!

    If you have to keep your ammo in anything other than “cool and dry” conditions, be cautious about firing it. Heat does strange things to the propellants, and prolonged exposure to high heat can have some unexpected results. I’ve a friend of mine who was a cop in Arizona, and his department issued him carbine ammunition that they insisted on him keeping with the rifle in his cruiser’s trunk. It was an accountable item, and they didn’t replace it for years and years–First time they went to actually use the stuff in an emergency, they got half-a-dozen misfires out of the first magazine. I forget what brand it was, but it was not your usual cheap-ass reload. It was, however, not loaded to military specifications…

    Typically, if you buy milspec ammo, it’s going to be thoroughly tested and loaded to accommodate any lot variations in propellant behavior. Civilian loads, not so much–But, as I have related, even the military specification stuff can go wonky.

    • “Typically, if you buy milspec ammo, it’s going to be thoroughly tested and loaded to accommodate any lot variations in propellant behavior.” If it’s from an arsenal that tested, was made when there was time to test, and it’s brand new.

      The older and farther it gets from a rich country manufacturer, the riskier it is. That Turkish and Syrian stuff from the 1950s is components only.

  26. There’s another forum discussion where a couple of the posters have pointed out the risk of shooting sabots through a barrel with a muzzlebrake. The petals of the sabot start to peel as soon as it leaves the barrel and can get caught up in the flutes of the muzzlebrake. One symptom of this is the shots going wildly off the point of aim, which is exactly what’s going on in the video. Also note the relative lack of a muzzle flash on that last shot, so I’m thinking that the barrel was actually obstructed (not a cartridge detonation)! The load could have been hot (AP ammo typically is), but shooting SLP’s through the rifle looks like a major contributing factor…

    • The pressure spike happens before the bullet leaves the barrel. If the pressure spike is greater than the gun can handle it blows up before the bullet leaves the barrel. Why would you expect a muzzle flash?

  27. I was a bit surprised that you didn’t mention squibs in the context of MGs in this and your “cheap ammo” rant.

    A squib in full auto can blow up the gun before you can react if it is capable of cycling the action. I was actually concerned about that when John Keene was demonstrating the ammo in the Lewis gun as I he seemed a bit too reflexive about pulling the charging handle, both from the squib and hang fire perspective. It made me uncomfortable even though I knew nothing had gone wrong. I’d have been quite concerned if I’d been there.

    I’d really like to see a series reviewing the evolution of design measures to deal with case failures. You’re uniquely positioned to do that.

  28. Jack Belk’s book, “unsafe by design” covers a lot of the ground about the subtle design features which contribute to (or detract from) making a gun as safe as possible for the firer and those around them.

    You could get it in dead tree from the online sellers,

    It is also available as free download from Jack’s page

  29. A gentleman who never taught me in a formal setting, but who I learned a lot from informally…

    In his early career, he’d been one of the stress engineers at AVRo, on the design team for the Shackleton.

    At the end of his career, he was renowned for being able to get college students (who had had fourteen years of school teachers making mathematics poisonous…),

    To be able to break down, understand and use engineering mathematics. Maybe even to start to enjoy mathematics, as the beautiful system of logic that it is.

    He had run the calculations on threads.

    Assuming that the wall (nut, cap, whatever) around the female thread is thick enough that it doesn’t just stretch and let the thread slip out of engagement,

    With a standard coarse V thread, say, Whitworth or metric coarse,

    There’s sufficient shear area with about 1.5 turns of engagement, to break the bolt rather than strip the thread.

    Things get rather more interesting with square threads (I’m not sure why you would ever want to use a square thread, when acme type threads are easier, stronger and work very well for precision lead and feed screws).

    I’ve seen a square thread subject to repeated shock loads, where the female thread had entirely failed at its root and was still wound like an ugly square section coil spring, in the male thread.

    Square threads seem to have been beloved by British and American state sector gun makers.

    Mauser, generally seems to have had better sense, although for some odd reason, The bolt cap on the 98/13 bolt action used a square thread.

    It would be very interesting to get a good look at the threads on that KB’d Serbu.

    If I was Serbu, I’d be ringing the guy three times a day for an appointment.

    If we are open to it, our mistakes teach us far more than what we get right (right for the moment – that “right” might yet ripen into a mistake)

  30. Mind you, sods law; it would happen to a guy on a channel called “Kentucky ballistics” which I understood to be a colloquial, if not widely used term of common parlance for… Exactly this.

    Source: Tennessee, older bloke… .45, wild bill… Something.



    “Deer at 600yrds? Use 3 times the powder.”

    As defined by the good citizens of Kentucky.

  31. I’m thinking that it may be a little premature to condemn the rifle on this.

    In all probability, your culprit is the SABOT round. Especially, if the ammo was older (Scott’s Kentucky ballistics segment post-accident mentioned it was) and that more specifically, it was the plastic sabot to blame here. If everyone goes over to KB and watches Scott’s own footage for the segment with the failure, you’ll notice that in the shots leading up to the failure, that the rounds that he is firing are having some issues with placement; He doesn’t appear to be shooting at a very great distance (In the video, he’s rather close, somewhere around 100 yds.) And his rounds are flying WAY off of bore center, where a .50 BMG should be within an inch or so of point of aim. That right there could indicate several things…Plastic choke/buildup happening rapidly (especially if the Sabots are 10+ years old) and perhaps even sabot fracturing or destruction on each shot. I don’t remember Scott looking down the bore post-explosion…I’ll go back and watch the vid again, but it’s very possible that what happened was that upon detonation, a round cock-eyed in the bore, and created just the sort of over-pressure obstruction that resulted in the catastrophic failure of the breech. Everyone has to keep in mind, that when CUP pressures are measured, it’s in a test barrel that allows the bullet to travel freely, and exit the test barrel, and not in a static, sealed barrel. An obstruction in ANY firearm could be capable of doubling or even tripleing the CUP pressure generated, far above any proving of said chamber/barrel. To that end, the SLAP rounds do have some history…the .50 round seemed okay in service, but they had many problems with the 7.62mm NATO version, so much so that developement was discontinued, and a lot of the problems stemmed from the Sabot’s. You can read some of it here:

  32. Have You read this yourself?
    Where does it say about “high pressure breaking the bolt”?

    This is not there and cannot be.
    Because any problems that arise in the muzzle when the projectile passes it (that is, at the end of the shot) cannot in any way affect what occurs at the highest pressure (that is, at the beginning).

    Anyway, this is what SHOULD happen when the locking assembly is designed CORRECTLY.

  33. Perhaps, if it turns out to find the remains of brass, it will be possible to understand whether this shot was made of brass?
    I think this can be easily verified.
    You just need to reproduce the “shot of brass”.
    If I’m wrong, nothing bad will happen.
    Anyone want to try?
    A place in the hospital (I sincerely hope) has already been vacated.

    PS Pardon, if I sound a little harsh.

    • And it is not necessary to perforate the brass.
      A cracked primer (this is even more likely) may well be enough.

  34. Shooting glasses saved him, as did not shooting alone.


  35. Appreciate what you are saying, and your Erudite discussion, However, the pressure spike evidence indicates excess chamber overpressure, not a bore obstruction. Shearing all the threads indicates 120,000-160,000+ psi and is most likely a fraudulent, homeade SLAP round with high energy pistol powder (Bullseye, etc.), coupled with a fake sabot (non-segmented and improper material), plus there was no evidence of crimping. Otherwise your discussion is excellent. Forensic examination for traces of pistol powder, case melting, and other evidence of gross overload, is where the discussion should start. A typical case rupture results in relatively minor damage to the gun and relatively minor damage to the shooter.

    This is NOT an endorsement of the Serbu basic design. Which I believe is inferior to ANY locked breach with multiple, over-designed lugs including safety lugs, and post breach bolt stopping mechanisms.

    Bruce Hunn, US Army Research Lab, retired.

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