Kentucky Ballistics gun explosion

Tosh.

A stalling position.

He has not addressed the fact that it was not the cap that stripped, it was the barrel threads that sheared. The steel, and hardness/strength of that portion is not under his control AFAIK.

Blustering about his Ukranian friend's analysis at a distance is far from convincing. I could do that too, now knowing that it is a 1.5" x 12 thread.

And, BTW, only three and a bit threads were engaged, by design, so it is blindingly obvious that only three and a bit threads would be sheared. Blooming obvious.

From what I can see he gets the barrels in from ??? then turns a miniscule thread on the end. Then welds them onto the rest, also heating up that portion. Previously using a dope head to do this "ha ha". His demonstration of his own Tig welding skills elsewhere were lamentable. As were his attitudes to safety, in every respect. And his p**s-poor analysis of strength of materials in gun design, in another of his videos.

Certainly the ammo may have been at fault as well, but who knows ?. Who will ever know, if "Scott" sends it to him, along with the bits. I doubt that Serbu is competent to analyse it, nevermind has access a pressure test lab. This will only go one way, and Serbu has yet again revealed his bias/denial.

He has not yet received the bits back from the "heroic" gullible/stupid man who seemed to think that he was invincible, and seemingly was. Well he also has had major views on his youtubery and tee shirt sales, so not doing so badly considering his idiocy.

FFS, he had also been putting Raufoss through it, for sh*ts and giggles. Or so he claims.

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Also BS about how the sticky up lugs were actually strong enough to restrain any foreseeable event.

Not that any safety features were necessary because it was so vastly stronger than could ever be required.

In any case, it's all about the ammo, the gun is unquestionable ? Predictable.

No news here, and probably never will be, ISTM that he is well out of his depth on this one.

Seriously I am very bored with this, and hope never to have to see his shonky guns. Honestly I doubt his (late learned) engineering credentials, and am aghast at some of his attitudes. As for the chap who is/was cosying up to his daughter, whom he humours, and whom he built this for, well, he is certainly an odd one.

But, hey ho, he has delivered at least $1,300,000 worth of these things already and is apparently backed up with many more orders, according to him. It's the American way.

Why are we bothering to discuss this ?
 
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Some more Edukation:

I take issue with the latest analysis that Serbu has quoted.

Firstly, lets start off with why Serbu decided to heat treat the cap to increase it's strength. He said in his previous video that he wasn't happy with leaving it untreated, that the margin of safety was lower than he liked. So he heat treated it to increase the strength. However that was meaningless unless the external threads on the barrel were also heat treated to strengthen them as well, which I suspect they were not.

If we assume that the barrel was manufactured using standard 4140 chrome moly steel, possibly also stress relieved before being drilled and rifled. It would not have been heat treated afterwards. Or perhaps it was made of some other variant.

If so the yield strength of the barrel threads would be expected to be 60,200 psi per AISI 4140. See AISI 4140 Alloy Steel (UNS G41400)

As Fastener Bolt Thread Stress Tensile Area Table Chart | Bolt Critical Thread Stress Area Chart - Engineers Edge state, the stress area of the thread of a 1.5" x 12 UNF thread is 1.581 in^2

It is not possible to consider any load sharing by multiple thread engagement, the cap is only fitted finger tight. At the moment of firing the loading is extremely dynamic, and the threads may be expected to fail one by one. This certainly looks like the failure mode experienced, judging by the picture in the video.

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I see signs of only three threads having been in full engagement.

I also see evidence that the case head separated, leaving the rest of the casing in the chamber. (My red arrow). This would certainly have caused gas pressure to build up inside the cap, so the force on it would have been "bolt thrust" plus lots more.

The analysis in the latest video also assumed that proof pressure of .50 BMG is 65,000 psi, whereas as I have explained previously, NATO proof pressure is actually 75,608 psi.

It also assumes that the bolt thrust is applied to an internal case head diameter of 0.68" I don't know whether this is precisely correct, but for the sake of argument lets assume so. Actually 0.680" is simply the diameter of the groove behind the rim of the cartridge.

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So, looking at this backwards, on the presumption that there was a case head separation that released the gas pressure into the un-vented cap, inside diameter 1.5", what pressure would be required to blow it off the threads ?

Answer: 60,200 psi yield strength of steel x 1.581 in^2 of thread area = 95,176 pounds. Applied to 1.767 in^2 of inside cap area = 53,851 psi.

From Wiki:

Average chamber pressure in for this round as listed in TM43-0001-27[8] the U.S. Army Ammunition Data Sheets —Small Caliber Ammunition, not including plastic practice, short cased spotter, or proof/test loads, is 54,923 PSI (378 MPa or 3,787 bar). The proof/test pressure is listed as 65,000 psi (448 MPa or 4,482 bar).

And as I said previously,
NATO 12.7x99 is the .50 BMG. Loaded "over pressure" compared with civilian stuff.
Service pressure 60,481 PSI. Proof pressure 75,608 PSI.

So, what might cause a case head separation ? Often this can be attributed to excessive headspace and/or multiple reloadings. When Serbu reamed the chamber, did he get the headspace precisely correct ? Was the suspect ammo in fact some sort of counterfeit dodgy reload (lots of it about, so it would seem) that might have been reloaded multiple times, with or without correct shoulder position ? Miltary ammo is never intended to be reloaded BTW, that is not a requirement of the brass design, and certainly not stuff that has already been fired out of the machine guns for which it was intended, and maybe sold as scrap, then "re-purposed".

BTW all these calculations are considering the ultimate yield strength of the steel, for catastrophic failure. No consideration has been given to what would be the design principles for normal operation, well within the elastic limit, and expected number of fatigue cycles. Which would have to use a lower figure. Typically half.

Applying that "rule of thumb", going back to the bolt thrust in normal operation, assume 0.680" case head internal dia., service pressure 60481 psi. Thus therefore bolt thrust = 21,967 pounds. Cap comes off at 95,176 pounds. Derate that by factor two rule of thumb. Now we have a "safety factor" for the design of 2.16. Which, on paper at least, seems plausible. But there is no safety at all in a case head separation. Quite the opposite.

Well that's my best guess, for now, at what happened, unless my eyes are deceiving me.
 

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Fascinating insight thank you. For me the scenario is “I have this old military round, dunno what it’s like but why don’t you try it in your rifle?”. Soooooo if you have any doubts whatsoever, and if it is of unknown or even slightly dubious provenance, forget it!
🦊🦊
 
The chump actively sought out these "SLAP" rounds because it's what he does (did). Along with other oddball stuff. For entertainment purposes. He even said that they came from a dubious source, and supposedly paid $100 each for them (which is scarcely believable), and asked for leads as to where he could get more.

I think it is entirely possible that they were extremely dodgy and may have been the root cause of the kaboom. Nevertheless my armchair analysis was aimed at the possibility of fatigue in the barrel threads over repeated shooting of dodgy ammo, together with a simple analysis that suggests a major gas leak, such as a head separation, has nowhere to go except to blow off the cap, which it can easily do, since no consideration has been given to this possibility, in the design.

All is speculation and surmise, particularly for Serbu, since he hasn't even seen the wreckage yet but takes every opportunity to blame the ammo and defend his toy. Watch this space.
 
To be honest if asked I would have said Demolition ranch was most likely to suffer this.
Gun safety does seem to be pretty low on the agenda of most channels like this.
Youtube may not have banned them, yet, but they de-monetised the channels, although ebay
seem ok with still selling advertising on the back of them.

Neil.
Yeah, and too bad it wasn’t! I can’t stand that punk from Demolition Ranch.
 
Whilst we are waiting for the next gripping instalment of this, some facts and data about SLAP rounds, from the people who make them, and/or the powders that are purposed for them. Rather specialised.

Not giving away any secrets here, I think. From this 2011 paper (not so old).

Should be easy enough to detect a counterfeit, apart from the wrong looking sabot, maybe without the pusher inside, but the the penetrator is tungsten carbide. Easy enough to distinguish from something knocked up out of steel etc. Magnet test or just try to scratch it. And of course, the headstamp.

And, BTW, the sabot means another 18% more case capacity, added on to the already underfilled case, when using standard WC860 propellant (read the full paper). Recipe for disaster with even more wrong powders.

Probably grist to Serbu's mill. But he has got to expect these kinds of things to be put through his rifles, he encourages it.

BTW the genuine SLAP sabot is designed not to chamber into a standard rifle. An attempt to prevent them being shot out of such things. The counterfeit ones are intentionally made the opposite way. The chump knew this and asked for his gun to be chambered specially to accept them. Which Serbu did for him. So he didn't not know.


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How do you know he had it re-chambered?
Because I do know.

How do you not know ? Try doing your own homework.

1: The standard chamber in the standard RN-50 will not accept SLAP rounds. Neither will they fit into SERBU's other .50, nor most other .50s The cylindrical sabot will not fit into the lead of a standard chamber, cut for the ogive of a standard bullet shape.

2: The chump had Serbu make him a special one, not "re-chambered" but built as such. Because he wanted to shoot these "mean rounds" through it. With a looser machine gun chamber, that also accepts the sabot.

He states this in his videos. Whilst displaying a degree of ignorance as to what he was doing. Serbu made it for him, in full knowledge of what was going to be put through it.

See at 5 minutes in.

Also see at about 12.5 minutes in. Where he also mentions that his slacker chamber is a bonus because he can just take out the fired cases with his fingers instead of having to lever them out of a standard chamber (no extractor in the design).

Seems to me like a case head separation just waiting to happen. Machine gun chambers for machine guns only IMO.
 
Interesting, so he ordered a custom chambering from the manufacturer. I wonder what he asked for exactly - and what was actually delivered.
 
Interesting, so he ordered a custom chambering from the manufacturer. I wonder what he asked for exactly - and what was actually delivered.
Not at all interesting.

It seems that I do actually know more about this than you, despite your fascination with a stupid incident from far away.

When I make statements of fact, please do not question them without providing evidence to the contrary. a few seconds on Google would have shown what I stated as fact, to be true.

Otherwise you are in danger of coming across like a small child, constantly asking "why daddy ?" > simple explanation. "But why daddy ?" > more detailed explanation. "But why daddy, how do you know ?" Oh, go ask your mother.

When I make assertions, they are challengeable.

When I venture an opinion, that is wide open.

Take a lesson from Rumsfeld. :

Reports that say that something hasn't happened are always interesting to me, because as we know, there are known knowns; there are things we know we know. We also know there are known unknowns; that is to say we know there are some things we do not know. But there are also unknown unknowns—the ones we don't know we don't know. And if one looks throughout the history of our country and other free countries, it is the latter category that tends to be the difficult ones

You can't know what I know. I don't know what you do and do not know. Or what I do not know. Nor do either of us fully know what the known unknowns are (but I suspect I know more of them than you). Nevermind the unknown unknowns. Nor what Serbu knows, thinks he knows, and does not know. Plenty of other pundits venturing their opinions, some more knowing than others. These tend to be more measured in their opinions, particularly when not incentivised to blab about them on youtube etc. and cognisant of potential legal comeback if someone objects.

I would expect that Serbu's insurers and lawyers are taking a keen interest in developments, after all there are £1,400,000 of these things in circulation, so any re-call for modification, or scrapping, plus on-costs, would be concerning, or wheedled out of, leaving him a man of straw. I don't envy him his position. He has nowhere to run other than to defend his product to the hilt. And I think he would be best advised to go quiet until some more things are definitely known.

Out. Last time. Hopefully that wasn't too sharp ?
 
Sharpie - you need to take a chill pill. Discussions with random people on the internet should not trigger people like this.

As an aside,

Found another channel where they shoot all manner of 50 cal's including SLAP and some others.


They seem to be shooting through a non machine gun (looks like a semi auto). No chambering issues - unless they had a custom barrel too. They do state that the muzzle brake has been removed though.
 
the twelve rounds needed to go to a proof house/ballistic lab to measure the actual pressure, far better that just trying to repeat the accident.
 
All evidence destroyed. Cool. An extremely overpressure round, made up by (I'm guessing Mark Serbu) finally did what was expected. Serbu built the rifle, as a special, to chamber Raufoss saboted rounds. Which are not normal .50BMG fodder. He knew what he was doing.

Nor available on the open market, for good reasons.

So, Serbu made the rifle, specially chambered, for the chump to shoot "Slap" rounds, at a cast iron fire hydrant for ***** and giggles and youtubery finance.

What could possibly go wrong ? The dope bought the supposedly dodgy "Slap" rounds from a dubious source, and over-paid for them. Not much different from buying illegal drugs.

But somehow he is a hero, Serbu is a great man, all is good. The chap has achieved closure by facing up to what happened that day, re-created it, and internalised that it was just an awful accident, not in any way his fault or total lack of judgement. but God saved him. (introducing God in these scenarios is just playing to the crowds, who, sadly, are brainwashed that way, across the Pond.)
 
Oh BTW, he oiled up the "Slap" rounds to supposedly make them more easy to extract, Whirl's of course increasing the bolt thrust. Still didn't manage to make it blow up with any of them, though he did try. Until eventually he did it, with a ridiculous round, provided by ??? And, unsurprisingly, discovered that a single shot rifle does not manually extract a round designed for quite a different purpose, in a different mechanism. Actually this thing has no extractor whatsoever. It really is a POS Possibly inspired by a useless ****, keen on improvised guns, who is cosy with one of his daughters.

Serbu's judgment, knowledge and credibility is certainly in question.

This demonstration of the thing, does not impress me.
 
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