YouTuber Kentucky Ballistics almost dies from 50 cal explosion

I'm wondering if he remembers who sold him that ammo?

Why people keep getting stuck on the ammo being old is beyond me. You can clearly see that the ammo (SLAP-T) were reloads. The one screen shot showed the round with no factory crimp.

So it comes back to who loaded the ammo and what powder they used. It could've been loaded with a pistol powder. From what we see in the video, as soon as he pulled the trigger it went boom!

That leaves me to believe that the round could've been jammed into the chamber and the wrong powder used in reloads. I hope Mark looks into this end as it makes the most sense.

A rifle design like a pipe bomb open on one end. Overpressure Ammo......what could go wrong?

Mk-211 said:

So it comes back to who loaded the ammo and what powder they used. It could've been loaded with a pistol powder. From what we see in the video, as soon as he pulled the trigger it went boom!

That leaves me to believe that the round could've been jammed into the chamber and the wrong powder used in reloads.

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Yes, as best as you can tell on video, it went boom as soon as he pulled the trigger. There would be no discernible delay between when he pulled the trigger and when the gun came apart because that would have happened anywhere from immediately to within just a few one-thousandths of a second - the difference being so tiny so as to not be discernible by a human in real time or in the gross level of slow motion offered by YouTube (video frame rate with way too slow). Short of the video being made with an exceptionally high frame rate so as to produce slow proper slow motion, you are going to be able to see any of the detail necessary to make a determination of immediacy. Whether it happened when the trigger was pulled or after the bullet had traveled down the barrel some distance cannot be determined from the video.

Double Naught Spy said:

Yes, as best as you can tell on video, it went boom as soon as he pulled the trigger. There would be no discernible delay between when he pulled the trigger and when the gun came apart because that would have happened anywhere from immediately to within just a few one-thousandths of a second - the difference being so tiny so as to not be discernible by a human in real time or in the gross level of slow motion offered by YouTube (video frame rate with way too slow). Short of the video being made with an exceptionally high frame rate so as to produce slow proper slow motion, you are going to be able to see any of the detail necessary to make a determination of immediacy. Whether it happened when the trigger was pulled or after the bullet had traveled down the barrel some distance cannot be determined from the video.

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When the bullet travels down the barrel before the gun explodes, as it happens in case of an obstruction, the pressure quickly decreases to the point where the chamber can handle it, and it's the barrel that fails.

In this case, the damages indicate that the overpressure was generated immediately when the round was fired, whether it's due to bad powder, wrong powder, excess load, throat obstruction, ruptured case, or whatever.

The fact remains, as several have already pointed out: guns fail, for a multitude of reasons, and very often the failure is NOT due to the gun itself.

HOW a gun fails, however, is entirely dependent on the design of the firearm. A good firearm design minimizes the consequences of a failure for the shooter.

This particular design is DANGEROUS in case of a catastrophic failure. In my books it's in the category "don't fire this bugger": that was my first impression the moment I first saw one of these in a review on the Net. Ain't changing tack now...

Kano383 said:

When the bullet travels down the barrel before the gun explodes, as it happens in case of an obstruction, the pressure quickly decreases to the point where the chamber can handle it, and it's the barrel that fails.

In this case, the damages indicate that the overpressure was generated immediately when the round was fired, whether it's due to bad powder, wrong powder, excess load, throat obstruction, ruptured case, or whatever.

The fact remains, as several have already pointed out: guns fail, for a multitude of reasons, and very often the failure is NOT due to the gun itself.

HOW a gun fails, however, is entirely dependent on the design of the firearm. A good firearm design minimizes the consequences of a failure for the shooter.

This particular design is DANGEROUS in case of a catastrophic failure. In my books it's in the category "don't fire this bugger": that was my first impression the moment I first saw one of these in a review on the Net. Ain't changing tack now...

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The question at hand was whether or not one could tell the immediacy of the failure from the video. The quote was, "From what we see in the video, as soon as he pulled the trigger it went boom!" I stand by my assessment that no human can discern, from this video, the difference in time that a few thousandths of a second from when the trigger was pulled to when the failure occurred.

You state that the overpressure was generated immediately. Well, we know pressure was generated after the primer ignites the powder. That is, after all, how a gun works. How long it took for the failure to occur after that point cannot be determined from the video.

As I wrote earlier in this thread, I would have the powder residue analyzed if at all possible. Also any unfired rounds would be pulled and analyzed.

Mark gave an updated video today.

Ed Matunas once wrote an article on damaged guns and poor shooting: "It's not always the reload, but that is the smart way to bet."

Double Naught Spy said:

The question at hand was whether or not one could tell the immediacy of the failure from the video. The quote was, "From what we see in the video, as soon as he pulled the trigger it went boom!" I stand by my assessment that no human can discern, from this video, the difference in time that a few thousandths of a second from when the trigger was pulled to when the failure occurred.

You state that the overpressure was generated immediately. Well, we know pressure was generated after the primer ignites the powder. That is, after all, how a gun works. How long it took for the failure to occur after that point cannot be determined from the video.

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No one can use that video to pinpoint the millisecond at which the explosion occurred, of course... But from the damages shown in the video, one can positively state that the explosion did not occur because of debris obstructing the barrel just before the muzzle brake, or even because of a projectile lodged mid-way in the barrel: the mode of failure indicates gross overpressure in the chamber OR at the bolt face (as could happen with a ruptured case). This could be seen just from photographs, no need of a high-speed video for that.

Kano383 said:

No one can use that video to pinpoint the millisecond at which the explosion occurred, of course..

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And yet you are going with it happening "immediately" even though you don't know when. Bizarre. Since the order of events and timing are important and you can't tell when they happened, "immediately" isn't even a relevant term, now is it?

Double Naught Spy said:

And yet you are going with it happening "immediately" even though you don't know when. Bizarre. Since the order of events and timing are important and you can't tell when they happened, "immediately" isn't even a relevant term, now is it?

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This is becoming inane... Arguing on words for the sake of arguing? That bullet DID NOT travel down to the muzzle before the "bolt" failed, of this I'm sure even without having that rifle in my hands. I happen to fix guns for a living, and have seen enough kabooms to know the difference between a plugged muzzle and a plugged chamber. IF this my conclusion is proved wrong down the line, you'll have my apologies and a six-pack of whatever beer you like, and I'll go back to revise my books... meanwhile I stick with that.

Casefull said:

A rifle design like a pipe bomb open on one end

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I agree with that. After reading most of the comments re: the RN-50, I had to take a look at one. Let me just say this: I wouldn't shoot it with any type of ammo. Just the fact that the "breech" is un-supported would spook me. Couple that with 225-odd grains of smokeless powder going off less than six inches from the shooters face, and I'm 100% O-U-T out. Still, I'm happy that KB is still with us, and not hurt a lot worse than he is. However, I don't think my 700 or either of my Savages are going to let go with comparable ferocity and therefore the video gives me pause, but doesn't make me afraid to shoot my rifles.

Mac

Of course Mr Serbu was going to conclude that it was bad ammo in his fine rifle, and it may well have been. It will be interesting if he can tell what wrong powder it is, assuming that is the fault.
I know (post #44) that Varget won't blow up an AR50, so we will be looking for something even faster, maybe even "pistol powder."

"... Yes the breechplug is supported by fingers on the frame but still, it does not seem like a robust system, ..."

As I read the design and watched the video, the fingers on the frame are there to prevent closing the barrel in firing position unless the cap is screwed down completely. The fingers offer practically no support to the end cap if the cap threads fail. The video shows the fingers were broken off when the cap failed.

So I'll be bold and say it is not a robust system for multiple firing of SLAP rounds no matter how many ordinary .50 BMG ball rounds it successfully fired.

Checking the Wikipedia article,
Cartridge, caliber .50, saboted light armor penetrator (SLAP), M903
... For use only in the M2 series of machine guns. ...
Cartridge, caliber .50, saboted light armor penetrator tracer (SLAP-T), M962
... the M962 also has a tracer element for observing fire ... and is used only in the M2 series of machine guns.

The M2 heavy barrel machine gun without mount or tripod weighs 84 lb, has a heavy barrel designed to be air cooled under full auto fire and which acts as a heat dispersor. In case of a chamber explosion, the shooter has nearly two feet of a massive receiver, bolt, feed mechanism between him and the chamber. I will dare say the M2 does seem to be a robust design.

SLAP is no higher chamber pressure than Ball.
There is a statement that the Serbu barrel was chambered for SLAP.
The wrong powder reload theory seems the leading suspect.

Here is a pre-blowup video
https://www.thereloadersnetwork.com/2020/11/25/50-cal-slap-vs-atlas-stone-340-lbs/

Don’t buy SLAP rounds at the gun show

Did no one watch the latest video from Mark Serbu that I had just posted? In the video Mark stated that in order for those threads to break like they did, it would have exceed around 161,000 PSI, he has no idea where he came up with the 85,000 PSI originally. He also posted pictures of the SLAP round Scott used vs real SLAP rounds. Difference being, real SLAP rounds have slits in the sabot and also a crimp. Scott's SLAP rounds did not.

He speculates that the SLAP round could have been reloaded with pistol powder or a half charge, which apparently the latter could cause a detonation. Also, the cap screw on the prototype was not heat treated, however in the production rifles they did get heat treated. Scott should be sending Mark the rifle within the next few days, so we'll get some updates probably within the next couple weeks.

Ric said:

Don’t buy SLAP rounds at the gun show

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Or better yet, make sure they will not fire if you are unsure if they are safe.

Yeah, I watched it on arfcom yesterday when it got posted in the mega thread there.

The SLAP-T round in the pic is definitely a reload but the sabot part is real. If you look closely at the sabot you can see the marks in it that he said aren't there. The pic is a little blurry but you can see it.

He also said that the cap is easily 3x stronger than it has to be. In Scott's video you can see him screw it on and it went on easy, so there was no prior damage. That one round was so hot, when it fired, it did all that damage.

Slamfire said:

Even the manufacturer has no idea of the dangerous of old ammunition. This is the most worthless, rambling six minute video I have seen in a long time. And lacking the knowledge of burn rate instability, the maker offers this :“round was counterfeit, was screwy”. It is apparent, he does not know that burn rate instability, due to old deteriorated gunpowder, has, and will, blow up a firearm.

RN-50 Blow-Up

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Everything Serbu has said thus far has been CYA. KY Ballistics is making a mistake sending the gun back to Serbu for analysis. We will never know the real truth from an independent source and this will now join the ranks of conspiracy theories like the JFK assassination.

Elkins45 said:

Knowing that it failed in a manner so spectacularly unsafe to the shooter makes me want to never fire a gun of similar design no matter what the provenance of the ammo inside it.

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Agreed. I'm really hoping that the ATF gets involved and shuts this guy down.

D.B. Cooper said:

Everything Serbu has said thus far has been CYA. KY Ballistics is making a mistake sending the gun back to Serbu for analysis. We will never know the real truth from an independent source and this will now join the ranks of conspiracy theories like the JFK assassination.

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Too bad H. P. White labs shuttered.

While it would be interesting to know what caused the failure, in the end I doubt it will matter, except to Kentucky Ballistics. Because it was probably a problem of some type with the sabot round that caused the gun to fail. We know that kabooms can and will occur with any design, and we see how this design kabooms.

As mentioned earlier, the RN 50's design uses a female breech cap over a male threaded barrel/chamber.

The catch with this design as opposed to the almost universal "bolt male"/"receiver female" is that, in the event of a case rupture, the thrust is not anymore dependent on the case head's area, but on the entire cap's inner area.

In this case, even though it's difficult to get accurate measurements from pictures alone, the cap's "bottom" inner diameter is close to double that of the case head. This gives an area 3 to 4 times larger than that of the case head.

From my tablecloth calculations, using the figures mentioned by Mark Serbu himself for the threads' shear strength, a pressure as low as 60 to 70,000 psi exerted directly on the cap's inner face would be enough to fail the threads.

In the email published by Mark in his video, the last paragraph is a telltale: read it here



Read again:



Here, the 160kpsi have reduced to 37kpsi... If the case head alone exerts pressure on the cap, you need 160kpsi to generate roughly 60,000 pounds of thrust, which would shear off the threads. BUT, if the gases act directly on the cap, you only need 37kpsi to generate the same thrust (their calculations, they do have the exact dimensions and specs).

"Under normal circumstances this Cap never has to contend with Gas Pressure."

Yep... Under normal circumstances. Kabooms are by definition not "normal circumstances". IF that breech cap has to contend with gas pressure, then it's either very close to the thread's shear limit, or past that.

I disagree with the conclusion that vent holes would be useless: in the event of a case rupture, they'd be a life-saving feature.

Getting the ATF involved is not the answer! That would mean that the man would be visiting EVERY gun manufacturer!

Got a KB? Look out, Mr. ATF man is going to be visiting you! They would be visiting the big manufacturers more than they would the small ones.

Let's wait and see what comes of the whole thing before calling the feds!

Kano383 said:

As mentioned earlier, the RN 50's design uses a female breech cap over a male threaded barrel/chamber.

The catch with this design as opposed to the almost universal "bolt male"/"receiver female" is that, in the event of a case rupture, the thrust is not anymore dependent on the case head's area, but on the entire cap's inner area.

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This post is not to take issue necessarily with anything else in your post, but I think this idea that the "almost universal" design is that the bolt is male and the receiver is female is not quite right. And a bunch of folks have mentioned it. However...

In Mausers, Remington bolt guns, etc. The chamber holds the cartridge. The bolt is behind the cartridge. What holds the bolt there? The receiver. What holds the receiver there? Male threads on the back of the chamber (barrel) interface with the female threads on the receiver. When a Mauser or Remington bolt gun fails, where does it fail?

Also, the ears on the receiver on Serbu's design seem to be stronger (yes, even in comparison to their respective cartridges) than the "safety lug" on Mauser 98s, and nobody complains about the safety lugs on Mauser 98s being too weak.