YouTuber Kentucky Ballistics almost dies from 50 cal explosion

Double Naught Spy said:

And we know this because we have all done a metallurgical analysis of the rifle to make sure it was okay?

We can't know one way or the other at this point as to why the rifle failed.

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Yep, should have added "probably"...

Let me rephrase: "It's probably not the rifle's fault, just like it's not the car's fault if a drunk driver hits you in a frontal collision. Yet, it makes a big difference to you if the car has seatbelts, airbags, and a collapsible steering column instead of having an old fashioned steel rod aimed right at your chest, with nothing to hold you back."

bat said:

No, additionnal threads would not prevent a catastrophic failure that already has exceeded the initials threads resistance, as the same causes results in same effects: failure of the threads under extreme pressure. Same threads, same pressure, same failure. (think of a cascading failure)

It may sound counter-intuitive that more thread add only marginally in the resistance and nothing in redundancy again an overpressure, but hey! Science!

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General accepted practice for a threaded connection is a minimum engagement length equal to no less than the diameter of the connector. Surely there must be a reason for that?

Wouldn’t more threads mean a longer delay between the first failure and all the others, potentially giving time for the barrel to uncork and the pressure be released? Or would the failure cascade be instantaneous?

Double Naught Spy said:

And I am sure hot gasses and corrosive powders also took their toll on those threads over time as well.

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The barrel was likely not that old, the video where said he got the new barrel for the SLAP rounds was 5 months ago, so I’d say its safe to assume the barrel was in the neighborhood of 6 months old.

Elkins45 said:

General accepted practice for a threaded connection is a minimum engagement length equal to no less than the diameter of the connector. Surely there must be a reason for that?

Wouldn’t more threads mean a longer delay between the first failure and all the others, potentially giving time for the barrel to uncork and the pressure be released? Or would the failure cascade be instantaneous?

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I admit I have no sure and clear answers for your questions.

But Backyard Ballistics made another good point in the video: looking back at some documentation, in my case, screws certifications, I see screw order by classes, each class having a Mechanical Resistance in MPa (rupture) and elasticity (deformation). For example, a "12.9" screw class having a 175kp resistance to rupture.

A .50BMG round will only produce 55kpsi, so, we are fine! But it's 55kpsi, pounds per square inch.
And in the scenario of a ruptured case and gas leak, the design of the RN-50 cap, would probably lead in pressure in all the breach cap inner surface, as demonstrated in the video, multiplying the total amout of force exerced in the breach cap.

This sort of breach design for example, is probably better in that case:



But causes others problems, like, extraction of the empty round

It's interressing to look at the enginering challenges of making a new design of firearm! (not that I ever intended to make one, it's just curiosity)

bat said:

No, additionnal threads would not prevent a catastrophic failure that already has exceeded the initials threads resistance, as the same causes results in same effects: failure of the threads under extreme pressure. Same threads, same pressure, same failure. (think of a cascading failure)

It may sound counter-intuitive that more thread add only marginally in the resistance and nothing in redundancy again an overpressure, but hey! Science!

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not directly related, but i can give you a real world example. Honda oil pan drains have about 1/4" of thread, while VW have about 5/8". Both use some soft alloy aluminum pans, and steel screws. VW's strip the pan around 50X as frequently as Honda's, despite being torqued to lower pressure. That torque from the bolt applies that force to each thread, so more threads don't really help much.
As far as this rifle, more threads can help, but you would need a wider shank to actually make an improvement. Then you have a lot of weight added, and the receiver needs more lathe time, heavier stock, and the price point goes up. At some point it goes up enough that they should have just done parallel threads, and an interrupted breach.

Double Naught Spy said:

And we know this because we have all done a metallurgical analysis of the rifle to make sure it was okay?

And I am sure hot gasses and corrosive powders also took their toll on those threads over time as well.



The video is really interesting. In addressing the number of threads, the speaker says extra threads would make no difference because the load is only carried on the first 4 threads and virtually none of the load is carried on the rest of the threads. While this may be true, it is only true so long as the first 4 threads remain intact. Loss of those threads would result in the load being transferred to other threads, if they were present. In other words, if only 4 threads are being engaged and the load is only carried on 4 threads, then there is no margin of safety or redundancy present.

edit: redundant comment, but it is a good point.

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It at any point corrosive gases reached the breach under pressure, that rifle was extremely defective. Brass should seal that chamber when the bullet hits the rifling instantaneously.
Full pressure ammo should have done that, especially brass, and its unlikely the breach threads ever saw serious gas or heat.
As for the threads, that redundancy doesn't really work. By the time the first fail, the pressure and velocity are the same, but momentum has gone up. Additional threads make more shrapnel. A big, single safety lug would be a better design. An interrupted thread breach plug with a something like a slide in safety lug to hold the firing pin would be ideal, but cost.

Double Naught Spy said:

And we know this because we have all done a metallurgical analysis of the rifle to make sure it was okay?

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And, apparently, the gun is going back to the maker for analysis, so the result is a foregone conclusion: failure caused by poor quality ammo.

D.B. Cooper said:

And, apparently, the gun is going back to the maker for analysis, so the result is a foregone conclusion: failure caused by poor quality ammo.

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The absolute last person I would send it to unless he’s a close personal friend of Scott and actually wanted to find out the true cause of the failure.

mjsdwash said:

It at any point corrosive gases reached the breach under pressure, that rifle was extremely defective. Brass should seal that chamber when the bullet hits the rifling instantaneously.
Full pressure ammo should have done that, especially brass, and its unlikely the breach threads ever saw serious gas or heat.

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Cases can fail and leak gases. Either semingly randomly on the case, like that, even on new and manufactured ammo:



Or, a well know problem if you reload your cases many times, head-case separation:



Head-case separation can also happen if you have a round calibrated "too short" for the chamber for some reason.

It's not common, but it happen sometimes.

Admitting that it's probably about the worst way to assess a person's work, but just going by the videos I've seen I'm willing to extend some good faith to Mark Serbu.

The rifle really needs a better failsafe. But honestly everything really seems to point to ammunition weirdness, hopefully they can put together something to improve the rifle moving forward but I don't think the manufacturer needs to be run out on a rail.

You are a lucky man.

Russell13 said:

Have any of you have a round explode in the chamber?
I’ve heard this happens sometimes with hand loading and being run to hot. I shoot only factory ammo and have never experienced it.

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43 year handloader here and no blowups. However, never overload and work loads up.

Never paid so much attention.
Glad he is ok and telling the funny of it. However, I knew was about to happen son or later they played to much (even with safety precautions) its a dangerous game.
Putting an old/obsolete round in a rifle knowing nothing about it (aka pressures) is a call for paramedics for sure.

I was thinking about the comment about SLAP rounds being meant for the M2 only...

Is it an issue of the round being loaded to higher pressures, or the sabot not melting in the hot barrel by virtue of machineguns being open - bolt designs?

bat said:

Cases can fail and leak gases. Either semingly randomly on the case, like that, even on new and manufactured ammo:

View attachment 996083

Or, a well know problem if you reload your cases many times, head-case separation:

View attachment 996084

Head-case separation can also happen if you have a round calibrated "too short" for the chamber for some reason.

It's not common, but it happen sometimes.

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yes, your absolutely right, but its a rare occurrence on factory ammo, in a cal and action that strongly discourage heavy use. The only way you'll see that as a long term erosion factor is in a barrel with extremely loose headspace, or several inches of freebore, or hot reloads on the same case too many times. I think in this case, its unlikely that gas/corrosive priming compounds damaged the threads. Certainly I have seen several neck, and casehead failures, but all in cases reloaded 5 or more times, or in rifles that eat a No-Go effortlessly.

The Glockodile said:

I was thinking about the comment about SLAP rounds being meant for the M2 only...

Is it an issue of the round being loaded to higher pressures, or the sabot not melting in the hot barrel by virtue of machineguns being open - bolt designs?

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From the limited information I can find, SLAP ammo has a muzzle velocity of around 4000 FPS and was designed for the M2. Guessing it might have something to do with the pressures and muzzle velocity. Wonder if any Gulf War vet who worked with the ammo could give us some information on it.

Well that’s not a good time.

Barrett made some M82's with SLAP chambers that were used in the first gulf war. They didn't make any more as the M82 isn't that accurate to begin with and the SLAP chambers didn't help.

Here's a good page for 50 BMG.
https://www.inetres.com/gp/military/infantry/mg/50_ammo.html

bat said:

Cases can fail and leak gases. Either semingly randomly on the case, like that, even on new and manufactured ammo:

View attachment 996083

Or, a well know problem if you reload your cases many times, head-case separation:

View attachment 996084

Head-case separation can also happen if you have a round calibrated "too short" for the chamber for some reason.

It's not common, but it happen sometimes.

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Thinning brass case head separations normally just result in extracting the case head and having to fish out the front section. They usually don’t give you a face full of gas.

I mentioned a serious case head failure from corroded brass in an earlier post. What made it so dangerous was that the brass failed much closer to the rim where the brass normally doesn’t obturate.

Mk-211 said:

Barrett made some M82's with SLAP chambers that were used in the first gulf war. They didn't make any more as the M82 isn't that accurate to begin with and the SLAP chambers didn't help.

Here's a good page for 50 BMG.
https://www.inetres.com/gp/military/infantry/mg/50_ammo.html

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That article you listed states that Barrett only did the MK211 chamber for the M107, more specifically the M82A1A was made for the Raufoss MK211, not the SLAP or SLAP-T.

The link I posted is about 50 Cal ammo, there's no mention of the M82 in it.

Mk-211 doesn't require a special chamber, only SLAP ammunition does.

Anyone catch this video?

Never would've thought about the muzzle brake as a potential problem. TL,DW; basically plastic from the sabot built up in the muzzle brake causing an overpressure and blowing up the gun on Scott.

Hunter 08 said:

Never would've thought about the muzzle brake as a potential problem. TL,DW; basically plastic from the sabot built up in the muzzle brake causing an overpressure and blowing up the gun on Scott.

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When Black Cloud shotgun shells came out I heard of a few people that said they had barrels split open when combining the black cloud with “Wad Stripper” chokes. I remember mainly because at the time I was trying black cloud with a pattern master choke, I stopped but I never really got any confirmation if it was a real problem or just one of thing that “somebody said”

I know it’s not the same thing but it could be the same principle.

Hunter 08 said:

Anyone catch this video?

Never would've thought about the muzzle brake as a potential problem. TL,DW; basically plastic from the sabot built up in the muzzle brake causing an overpressure and blowing up the gun on Scott.

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Interesting video. As I mentioned back in post #19

Double Naught Spy said:

At Barrett school, we were told NEVER to fire SLAP rounds through our Barrett's unless we first removed the muzzle brake because of the potential for catastrophic failure. They never went into what that failure would be, however.

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So we are back to over pressure, but not because of a misloaded round, but because of an obstruction caused by the sabot and the muzzle brake combo.

Still don't buy that, if the round contacted the muzzle brake, the brake would've been blown off. There would've been shrapnel blown out all over the place.

The KB came from the receiver, only time will tell if we find out any info on the ammo. If he has any leftover and it shows that the wrong powder was used... there's the smoking gun.

It still could've been a combination of the round being extremely hot and being jammed into the chamber.