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Main Forums => The Roundtable => Topic started by: MechAg94 on April 30, 2021, 10:44:22 AM

Title: Kentucky Ballistics - My 50 Cal Exploded
Post by: MechAg94 on April 30, 2021, 10:44:22 AM
https://www.youtube.com/watch?v=1449kJKxlMQ

Kentucky Ballistics was injured when his 50 cal Serbu rifle came apart with an overpressure round. 

I saw some mention of this on Instagram this morning from others.  I don't follow Kentucky Balistics.  All of it was caught on video.  He mostly okay (recovering?) since he is narrating and explaining what happens.  The rifle goes to pieces about 4.5 minutes in.

Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: AJ Dual on April 30, 2021, 10:49:01 AM
I was watching the video on that yesterday.

Punctured a lung, shredded his jugular, and messed up his left arm/index finger something fierce.

Moral of the story, don't shoot weird old .50BMG rounds.

Although the RN 50 seems like it has some design deficiencies if it fails in a KB.

Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: Jim147 on April 30, 2021, 11:01:09 AM
As I said in another site discussing this, if I was going to shoot .50 anymore I would pull bullets and load with a known powder to proper pressure.
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: Brad Johnson on April 30, 2021, 11:49:16 AM
As I said in another site discussing this, if I was going to shoot .50 anymore I would pull bullets and load with a known powder to proper pressure.

This. At the very least, mount it up and use some form of remote triggering. I certainly wouldn't be placing my fleshy bits anywhere near the firearm.

Based on what I saw and what was described, he was very, very lucky.

Brad
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: AmbulanceDriver on April 30, 2021, 11:59:13 AM
Apparently some super-hot SLAP round.   He didn't specify the source of said round (other than saying they go for about $100 a pop) but man.   The fact he survived is rather spectacular, and is completely due to his knowledge of self first-aid...  Had he not reached into the hole in his neck and clamped off his jugular with his thumb, he would have been dead - no doubt about it.
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: HankB on April 30, 2021, 12:05:42 PM
I remember reading some reviews (quite a few years back) on the Serbu that questioned its strength. For the rifle to fail THAT catastrophically in that manner, even with a round that was way over pressure, makes me never want to have a Serbu.

AND - perhaps most importantly - don't use oddball ammo you bought "somewhere." (A good policy for any gun, not just .50s.)
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: WLJ on April 30, 2021, 12:12:03 PM
Quote
The RN-50 represents the first time a production firearm has ever been inspired by social media. Designed in conjunction with YouTube celebrity Royal Nonesuch. The RN-50 is a unique approach to the .50BMG rifle. Rugged, lightweight, accurate, easy takedown and low price make this rifle a winner! The simple screw-on breech cap is not only strong, it applies absolutely symmetrical support to the cartridge case, allowing for incredible accuracy. Using top quality materials as well as parts from our proven BFG-50 rifle, the RN-50 gives you high quality at an incredible price, along with lineage to a safe, proven firearm that's been in production for 17+ years. Whether you're looking for the least expensive way to get into shooting .50BMG or you want to outshoot your friends' expensive match rifle, the RN-50 is for you!
https://serbu.com/rn-50/

Gives me a warm fuzzy feeling  :facepalm:
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: fifth_column on April 30, 2021, 12:14:13 PM
I think people are more likely to make stupid decisions when they're being recorded and know there will be an audience, or if they're in front of an audience.
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: lee n. field on April 30, 2021, 12:17:47 PM
https://serbu.com/rn-50/

Give me a warm fuzzy feeling  :facepalm:

Literally half the price of their base bolt action single shot .50.  MMMmmm.
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: MechAg94 on April 30, 2021, 12:22:04 PM
I was just thinking there may be easy way to make that screw on bolt stronger, but maybe not without increasing the cost. 

He noted that the rounds immediately prior to the last one were obviously hotter than the first.  I wonder if the first round was that hot if he would have thought more about that. 
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: WLJ on April 30, 2021, 09:17:25 PM
Ian (Forgotten Weapons) put out a video today on the subject of ka-booms

Earth-Shattering ka-Boom! How (and Why) Guns Explode
https://www.youtube.com/watch?v=71OGayW7CnI
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: bedlamite on April 30, 2021, 09:22:38 PM
I was just thinking there may be easy way to make that screw on bolt stronger, but maybe not without increasing the cost. 

He noted that the rounds immediately prior to the last one were obviously hotter than the first.  I wonder if the first round was that hot if he would have thought more about that.

My first thought was to wonder why they were using standard threads. Standard for heavy loads are ACME threads.
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: Angel Eyes on April 30, 2021, 11:03:12 PM
Ian (Forgotten Weapons) put out a video today on the subject of ka-booms

Earth-Shattering ka-Boom! How (and Why) Guns Explode
https://www.youtube.com/watch?v=71OGayW7CnI

Gun Jesus is informative as usual.  He made a good point about the Serbu barrel being stronger than that end cap, and if the opposite had been true, Scott would probably not have been injured (or at least not seriously so).

Off topic a bit: Ian also mentioned the perils of .300BLK in a 5.56 rifle, like this:  https://www.youtube.com/watch?v=RbfIkaNlECo

Not nearly as dramatic as Scott's kaboom, but interesting (to me at least) how the AR failed exactly as designed.



Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: French G. on April 30, 2021, 11:11:41 PM
Yeah, I will fault the design more than the guy who studied the design at contact distance. Really nowhere for a failure to go other than face.
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: MechAg94 on April 30, 2021, 11:33:42 PM
I was checking to see if that video was posted. 

I wonder if there is some sort of retro-fit they could add that would strengthen that system or add some sort of shroud that could contain a failure.  The Serbu is a very inexpensive 50 caliber rifle.  I am not sure what can be changed without adding a lot of cost. 
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: dogmush on May 01, 2021, 10:43:22 AM
I am intrigued by this design, and would like a closer look at it.  My .50 upper isn't known as the best ever, but it's designed with a vent that vents away from the shooter.  Wierd that Serbu doesn't have something like that.


ETA:

This pic shows threads that look like standard 60 degree threads.

(https://cdn11.bigcommerce.com/s-dmbfmt5mav/images/stencil/1200x1800/products/116/446/RN0025_1__72217.1604005225.jpg?c=2)
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: gunsmith on May 01, 2021, 01:22:11 PM
the video popped up as recommended, but I didn't view it.
unless I get lucky and become wealthy, I'm not buying .50 BMG cal anything .
 I would love to own a Barret tho.

 In a few years I hope to own a 7mm rem mag, probably as close to 50bmg i will ever get to
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: lee n. field on May 01, 2021, 08:06:48 PM
https://www.youtube.com/watch?v=5AY6iEVhJE8 (https://www.youtube.com/watch?v=5AY6iEVhJE8)

Mark Serbu comments on it.

Quote
Just a brief explanation of the RN-50 blow-up accident that occurred to Scott from Kentucky Ballistics.  I will be coming out with a detailed analysis video shortly after I get my hands on Scott's rifle and some of the ammunition he used.
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: JN01 on May 02, 2021, 11:21:33 PM
Back in 2014, a guy firing a Vulcan bolt action .50BMG was injured when the bolt blew out and was imbedded in his neck. https://www.military.com/video/guns/rifles/50-cal-blows-up-in-shooters-face/3223685684001

Another one kaboomed and injured a shooter when chambering a round: https://www.thefirearmblog.com/blog/2013/06/10/vulcan-v50-50-bmg-kaboom/

The moral of these stories is that if you want to buy a .50BMG rifle, trying to go cheap is a poor choice.
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: Zardozimo Oprah Bannedalas on May 03, 2021, 12:20:33 PM
I was just thinking there may be easy way to make that screw on bolt stronger, but maybe not without increasing the cost. 

He noted that the rounds immediately prior to the last one were obviously hotter than the first.  I wonder if the first round was that hot if he would have thought more about that.
I'm thinking drill a vent into the chamber like you have on the SMLE and others of the period, who were also dealing with widely varying ammo/brass quality and power levels. Ian's video on forgotten weapons touches on some of the methods used to prevent this happening.

Back in 2014, a guy firing a Vulcan bolt action .50BMG was injured when the bolt blew out and was imbedded in his neck. https://www.military.com/video/guns/rifles/50-cal-blows-up-in-shooters-face/3223685684001

Another one kaboomed and injured a shooter when chambering a round: https://www.thefirearmblog.com/blog/2013/06/10/vulcan-v50-50-bmg-kaboom/

The moral of these stories is that if you want to buy a .50BMG rifle, trying to go cheap is a poor choice.
I remember the Vulcan KBs, and I got that exact takeaway. A lot of ammo of questionable origins and storage, already expensive at the best of times. Don't take chances. I'm sure Scott's hospital bills were much higher than the cost of a Barrett, and that's even with a full recovery and no loss of eyesight etc.
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: K Frame on May 03, 2021, 01:00:10 PM
"I'm thinking drill a vent into the chamber like you have on the SMLE and others of the period"

I'm not sure that would work in a gun like the Sebu.

In guns like the SMLE, the Arisaka or the Springfield there's a lot of action behind the chamber/bolt head, making vents feasible for venting gas that gets back into the action. Those vents are there primarily in the event of either a pierced primer or a case head failure in an unsupported portion of the chamber.

In the Serbu, that screw up cap is the extent of the bold head... there's literally no enclosed action behind it of the kind there is on an SMLE, et al. It also means that, unlike most bolt action rifles, the cartridge head is fully support in the Serbu.

While I'm not 100% sure, it also appears that the mode of failure in this case was overpressure causing the cap/barrel threads to fail due to increased thrust against the threads. When the threads failed and the cap came loose there was no amount of venting in the world that would have stopped what happened.

As someone else pointed out, that's not the proper thread type for high strength.
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: MechAg94 on May 03, 2021, 02:24:41 PM
The other option besides a more expensive rifle is to pull bullets and reload every round with a known powder load. 
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: HankB on May 03, 2021, 02:28:13 PM
Venting gas from a blown primer or case isn't the same as restricting shrapnel from a catastrophic failure. Most bolt actions have an action stronger than the barrel - in fact, when P.O. Ackley was testing various military actions for strength via handloads that were deliberately made to produce substantial overpressure, he had to rebarrel some rifles with special heat treated barrels to keep the barrel from blowing off before the action let loose. IIRC, the only bolt action that failed in a catastrophic manner despite the most extreme overloads PO used was an Eddystone Enfield due to defective heat treatment.

Other actions that (from various sources) were problematic from the standpoint of shooter safety were low number 1903 Springfield actions (again, with bad heat treat) and late war Arisaka actions (some with no heat treat. Early Arisakas were among the very strongest military actions.)

I wonder about the ammo used in this Serbu blow up - since it may have been experimental, perhaps it incorporated a duplex/forward ignition system; Elmer Keith wrote about some .50 BMG ammo using this method that gained a couple of hundred FPS velocity, but it proved dangerous in oversized chambers. Or maybe the ammo had been cleaned up by tumbling - if the powder charge was rolling around loose in the case extreme tumbling may have ground down the powder to a finer consistency. And of course, undercharges in bottleneck cases can also be dangerous. But this is just pure speculation.
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: Brad Johnson on May 03, 2021, 03:44:37 PM
I wonder about the ammo used in this Serbu blow up - since it may have been experimental, perhaps it incorporated a duplex/forward ignition system; Elmer Keith wrote about some .50 BMG ammo using this method that gained a couple of hundred FPS velocity, but it proved dangerous in oversized chambers. Or maybe the ammo had been cleaned up by tumbling - if the powder charge was rolling around loose in the case extreme tumbling may have ground down the powder to a finer consistency. And of course, undercharges in bottleneck cases can also be dangerous. But this is just pure speculation.

Also possible that the sabot got pushed far enough back in the case during chambering, change in case volume causing significant overpressure. I've seen warnings about SLAP rounds being incompatible with some rifles for this reason.

Brad
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: Zardozimo Oprah Bannedalas on May 03, 2021, 05:02:17 PM
"I'm thinking drill a vent into the chamber like you have on the SMLE and others of the period"

I'm not sure that would work in a gun like the Sebu.

In guns like the SMLE, the Arisaka or the Springfield there's a lot of action behind the chamber/bolt head, making vents feasible for venting gas that gets back into the action. Those vents are there primarily in the event of either a pierced primer or a case head failure in an unsupported portion of the chamber.

In the Serbu, that screw up cap is the extent of the bold head... there's literally no enclosed action behind it of the kind there is on an SMLE, et al. It also means that, unlike most bolt action rifles, the cartridge head is fully support in the Serbu.

While I'm not 100% sure, it also appears that the mode of failure in this case was overpressure causing the cap/barrel threads to fail due to increased thrust against the threads. When the threads failed and the cap came loose there was no amount of venting in the world that would have stopped what happened.

As someone else pointed out, that's not the proper thread type for high strength.
Makes sense... it's all about the timing, and if threads are overwhelmed before the brass can give way it'll do nothing.
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: Jim147 on May 03, 2021, 05:08:10 PM
A sabot down a brake gives me the same not fuzzy feeling that a gas check sent down a canned rifle does.
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: French G. on May 04, 2021, 12:13:18 AM
Feel like a Ross rifle thing. Great rifle, may kill ya if you don't do it just so. Make a design with failsafes and actual bolt lugs. Single shot bolt AR uppers are not astronomical.
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: dogmush on May 04, 2021, 02:59:33 AM
Mark responds (sorta).

https://www.youtube.com/watch?v=5AY6iEVhJE8&t=340s


I think if you are designing firearms you really need to design the failure mode into it.  You can make the strongest gun ever, and some dingus will fill it with C4 and touch it off.  Failure mode design is as important, if not more, then the "normal use" engineering.
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: K Frame on May 04, 2021, 10:37:19 AM
The more I'm hearing/reading/seeing about this, the more I think it's not an issue with the rifle at all.

Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: makattak on May 04, 2021, 10:54:15 AM
I had to stop watching once he started talking about what he did to stop the bleeding. I was actually getting sick to my stomach when he talked about what he had to do.

He's amazingly blessed to still be breathing.
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: Brad Johnson on May 04, 2021, 11:05:10 AM
The more I'm hearing/reading/seeing about this, the more I think it's not an issue with the rifle at all.

Same. Everything points to a massive overpressure, something far beyond any safety margins that could be reasonably engineered into the rifle.

Brad
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: MechAg94 on May 04, 2021, 11:33:07 AM
The only fault with the rifle is in engineering the failure point so it does not endanger the shooter.  That doesn't mean they are at fault, it just means the owners should be aware of that and take precautions with unknown ammo.
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: K Frame on May 04, 2021, 12:54:39 PM
"The only fault with the rifle is in engineering the failure point so it does not endanger the shooter."

Realistically an impossibility in most, if not all, cases.

But, in this case, and as others have pointed out, I think the choice of thread type on the breech cap is a bit on the suspect side.
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: MechAg94 on May 04, 2021, 03:55:15 PM
I would be curious if changing the thread type alone would make enough of a difference. 
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: dogmush on May 05, 2021, 06:27:30 AM
Some interesting and more technical takes on the rifle design and failure mode here:

https://www.youtube.com/watch?v=bBNHI1_urWs

https://www.youtube.com/watch?v=p7LjeJNewBs&t=314s

One thing that caught my ear in the first video is the huge increase in bolt thrust for any given chamber pressure in this design if the case ruptures and gas gets behind the case head.  I hadn't thought of that, and .50 brass is pretty tough, but the difference in forces between 80,000 PSI on .75 sqin, and 80,000 PSI on 1.5 sqin is pretty large, and this breech design is particularly susceptible to that, if high pressure gas gets between the cap and the barrel.

I reiterate my opinion that this thing needs vents.
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: K Frame on May 05, 2021, 06:53:31 AM
OK, I was apparently wrong about the ability and usefulness of venting the cap.

Very interesting.
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: K Frame on May 05, 2021, 09:34:41 AM
Come to think of it... has the case been found? Has anyone examined it for failure mode?
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: dogmush on May 05, 2021, 10:12:30 AM
Come to think of it... has the case been found? Has anyone examined it for failure mode?

I thought Scott said he was sending all the pieces back to Serbu.  I assume that would include any pieces of the case he could find.
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: dogmush on May 05, 2021, 10:18:17 AM
Also, In the ultimate YouTuber "merch links in bio" move, He's already got "Just put a thumb in it" T-shirts for sale.

https://bunkerbranding.com/pages/kentucky-ballistics

 :lol: :lol:
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: WLJ on May 06, 2021, 05:50:12 PM
In case some weren't aware Ian of Forgotten Weapons had an "incident" himself although I don't recall if it was ever stated exactly what it was that occurred  beyond it was an out of battery. IIRC he still carries metal in his chest from it to this day.

Dangerous Things are Dangerous: The Importance of Medical Training
https://www.youtube.com/watch?v=-FhFw86Xk7o




Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: Zardozimo Oprah Bannedalas on May 08, 2021, 10:42:04 PM
Also, In the ultimate YouTuber "merch links in bio" move, He's already got "Just put a thumb in it" T-shirts for sale.

https://bunkerbranding.com/pages/kentucky-ballistics

 :lol: :lol:
Can't blame him there, I imagine he's gonna have some pretty impressive medical bills before long - on top of all the days of live-saving care, he had reconstructive surgery to his face.

In case some weren't aware Ian of Forgotten Weapons had an "incident" himself although I don't recall if it was ever stated exactly what it was that occurred  beyond it was an out of battery. IIRC he still carries metal in his chest from it to this day.

Dangerous Things are Dangerous: The Importance of Medical Training
https://www.youtube.com/watch?v=-FhFw86Xk7o





This is why I have 3 or 4 medical kits scattered everywhere - in the house, in the car, in the mall ninja vest, in the backpack for hunting/shooting range/hiking stuff. They don't have the most tactical tourniquet on the market, but they're inexpensive enough I could buy them and put them everywhere.
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: Hawkmoon on May 08, 2021, 11:07:54 PM
Some interesting and more technical takes on the rifle design and failure mode here:

https://www.youtube.com/watch?v=bBNHI1_urWs


First video -- when he got to the discussion of the number of threads engaged (around the 03:50 mark) I stopped listening. I just spent 7 years as an inspection supervisor on a major construction project. The number of threads engaged is a MAJOR concern, and to claim that even if there were 50 threads engaged only the first four would have taken 80% of the load is so totally off-the-wall that I'm not going to even finish watching the video.
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: dogmush on May 09, 2021, 12:56:16 AM
My machinist books teach a couple rules of thumb on threads.  One says that the strength of the bolt is reached around 3 threads (assuming same material).  The other says to design for 1-1.5x the diameter of the fastener for thread engagement.
Both say some version of there's no point in making a bunch of extra threads because the joint doesn't get that much stronger after the optimum thread engagement.

[shrug]
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: RoadKingLarry on May 09, 2021, 01:09:36 AM
How many threads are engaged in a typical large (>3/4") nut and bolt? At what point does it achieve optimal/max strenght?
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: Hawkmoon on May 09, 2021, 01:47:16 AM
My machinist books teach a couple rules of thumb on threads.  One says that the strength of the bolt is reached around 3 threads (assuming same material).  The other says to design for 1-1.5x the diameter of the fastener for thread engagement.
Both say some version of there's no point in making a bunch of extra threads because the joint doesn't get that much stronger after the optimum thread engagement.

[shrug]

Sure -- but what's the diameter of that breech cap? It had what, maybe four or five threads engaged?

I know in automotive suspension work, the commercial truck spring place where I get U-bolts for my Jeep leaf springs supplies the U-bolts with double-height nuts -- twice the height (and number of threads, obviously) of a standard hardware store nut of the same diameter and thread pitch. I assume they do that for a reason.
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: dogmush on May 09, 2021, 02:44:42 AM
How many threads are engaged in a typical large (>3/4") nut and bolt? At what point does it achieve optimal/max strenght?

According to Fastenal, a standard 3/4-10 NC nut is .656" thick.  so call it 6 full threads and a little extra.  (I note that's a little short of the 1-1.5x diameter my book says for making threads, but again {shrug} I'm not an expert by any means.)  As far as max strength, I assume that each added thread adds some strength, but the optimal thread engagement is where diminishing returns really take over.  Optimal strength of a threaded joint is probably usage specific.

Sure -- but what's the diameter of that breech cap? It had what, maybe four or five threads engaged?

I know in automotive suspension work, the commercial truck spring place where I get U-bolts for my Jeep leaf springs supplies the U-bolts with double-height nuts -- twice the height (and number of threads, obviously) of a standard hardware store nut of the same diameter and thread pitch. I assume they do that for a reason.

I think we've (the internet) have been saying it's about an 1.5 diameter, but I don't know how the fact that it's a donut plays into that.  It's not like a solid 1.5" bolt.

On the leaf spring thing I just put a lift on my F150, and it too has tall nuts for the leaf spring u-bolts.  Tall, grade 8 at that.  I'd be interested in why that got speced actually, I suspect that the pull on those bolts is really high, and uneven, trying to resist lateral movement of the axle when off camber or cornering. (the leaf spring would try and tilt on the axle with a lateral load, and one half of the bolt would be in compression, while the other half is in tension)  That may have some crazy loads, but the math is beyond me.

To be clear, I'm not arguing the RN-50 has "enough" threads, or that 4 is indeed the "right" number of threads like the video said.  I'm more trying to learn more through the discussion, and the extra research the discussion sends me on. 

For another data point Howitzers still use interrupted threads to close cannon breeches.  Here is the open breech of an M109 155m Paladin:
(https://www.tanks-encyclopedia.com/coldwar/US/photos/M109_open_BREECH.jpg)

Even halving the number because of the interruptions, that's more than 4 threads.
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: Hawkmoon on May 09, 2021, 09:50:18 AM

For another data point Howitzers still use interrupted threads to close cannon breeches.  Here is the open breech of an M109 155m Paladin:
...
Even halving the number because of the interruptions, that's more than 4 threads.

And those don't look like standard 60-degree machine screw threads -- those look more like Acme threads.
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: K Frame on May 10, 2021, 06:59:07 AM
"Even halving the number because of the interruptions, that's more than 4 threads."

I'd think you'd want/need additional thread engagement on an interrupted screw style breech because you're concentrating one hell of a lot more force on the threads that are there...

Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: dogmush on May 10, 2021, 09:46:56 AM
I would have spitballed that 16 half threads and 8 full threads should have similar strengths.
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: Hawkmoon on May 10, 2021, 10:48:41 AM
I would have spitballed that 16 half threads and 8 full threads should have similar strengths.

I would have said the same thing.

Quote from my first year structural engineering professor (best read with a heavy Scottish accent): "Stress goes where there's material there to resist it."
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: bedlamite on May 12, 2021, 08:57:41 AM
https://www.youtube.com/watch?v=na1Qo7FxDeM
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: makattak on May 12, 2021, 01:23:00 PM
160,000+ PSI?!?!

Wow.
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: dogmush on May 12, 2021, 02:00:23 PM
Counterfeit SLAP round maybe?  The crimp and sabot do look different.  That'd be a mother *expletive deleted*er.  I wonder if Scott has any left that he can have someone pull the bullet on and check out.  I'd be pretty pissed to find someone had sold me a .50BMG case full of Win231.
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: K Frame on May 13, 2021, 07:01:42 AM
That's a very interesting point about the possibility of it being a counterfeit round. It's decidedly different from from the several authentic slap rounds I've seen over the years.
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: Hawkmoon on May 13, 2021, 02:47:53 PM
Even if is was a faulty and/or counterfeit round -- the design of the firearm made the breech cap the weakest point, so that failure turned the cap into a projectile aimed at the shooter. Firearms designers (in general) learned a hundred years or more ago that the design should vent over-pressure away from the shooter, and the part that's going to blow up should not be the part closed to the shooter's head.
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: MechAg94 on May 13, 2021, 03:52:23 PM
Even if is was a faulty and/or counterfeit round -- the design of the firearm made the breech cap the weakest point, so that failure turned the cap into a projectile aimed at the shooter. Firearms designers (in general) learned a hundred years or more ago that the design should vent over-pressure away from the shooter, and the part that's going to blow up should not be the part closed to the shooter's head.
How many hundreds of years or more?

I wouldn't go back further than when the big innovations were adopted:  center-fire cartridges, interrupted screw, smokeless powder, mini ball, etc.
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: WLJ on June 16, 2021, 08:36:31 PM
Quote
markserbu
150K subscribers
I just received the RN-50 from Scott and here's a quick look at it.  There were obviously some HUGE forces at work here, and it's good that I've finally got my hands on this thing to start doing the analysis of what happened.

Kentucky Ballistics' RN-50 Blow-up: First Look
https://www.youtube.com/watch?v=4ny_V_VfT3Q
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: RoadKingLarry on June 16, 2021, 10:23:13 PM
Quote
analysis of what happened


https://www.youtube.com/watch?v=Ec-8A5k16Ak
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: Bogie on June 16, 2021, 11:55:07 PM
Primers start to flow at 60kish.
 
Over 100k? I'd expect serious kinetic disassembly.
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: WLJ on February 16, 2022, 11:04:59 PM
He recreates the incident/accident with the same model 50cal this time in a safe, for him, manner using rounds from the same batch.

My 50 Cal Exploded...AGAIN !!! (Recreating My Accident)
https://www.youtube.com/watch?v=hsw70VfSFFw




Spoiler: Far too hot rounds. Hasn't blown the gun yet though but I'm still watching

Edit: All the SLAP rounds were too hot but did not blow the gun. A final round purposely loaded to what they think the one on April 9th was loaded to did.
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: MechAg94 on February 17, 2022, 10:38:22 AM
Cool video.  Glad he was prepared with the overpressure round. 

I still think the Serbu doesn't offer as much protection for the shooter as other designs.  I think if I were to get a 50 cal rifle, I would lean toward other guns. 
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: HankB on February 17, 2022, 10:40:57 AM
Watched the video. The rifle stood up pretty well to some obvious overloads, but it reinforces my opinion expressed early in this thread NOT to fire questionable ammo from a gun show (or anywhere else) and if I ever get a .50 BMG rifle (which I think is unlikely) to avoid Serbu. I think some other designs have likely failure modes that may not be quite as catastrophic to the shooter as that rifle.

(I also avoid milsurp ammo that comes from countries where I wouldn't drink the water, like India or Zimbabwe.)
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: WLJ on February 17, 2022, 10:47:47 AM
Cool video.  Glad he was prepared with the overpressure round. 

I still think the Serbu doesn't offer as much protection for the shooter as other designs.  I think if I were to get a 50 cal rifle, I would lean toward other guns.

Yep.
The Serbu design while strong doesn't provide anywhere else for the an over pressure to go except straight back at the shoot if a guy named Murphy happens to comes along.
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: 230RN on February 17, 2022, 01:11:52 PM
Double post, sort of half expected it, sorry.
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: 230RN on February 17, 2022, 01:19:05 PM


(https://cdn11.bigcommerce.com/s-dmbfmt5mav/images/stencil/1200x1800/products/116/446/RN0025_1__72217.1604005225.jpg?c=2)

Cap threads looked OK for 40-60 psi household water pressure.

Sidewise relevance: Couldn't think of the name of that project to give dangerous ammo to the enemy.... "Project Eldest Son."

https://www.fieldandstream.com/blogs/gun-nuts/2011/10/project-eldest-son-covert-ammo-sabotage-vietnam/
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: BobR on February 17, 2022, 01:49:44 PM
^^^^^

Salting munitions is a popular way to deter people from using stolen munitions.

When we were in Djibouti in the late 80s we would go drinking with a few French Foreign Legion guys from the US. There was an issue with stolen hand grenades making it into the hands of rebels/etc. He said they would put instantaneous fuzes in 2 or 3 grenades per box and let them get stolen and put on the black market, etc. He said it cut down on the amount of stolen hand grenades from them because nobody that took them knew whether they would work properly or not. They also offered to get every one on the crew an AK pretty cheap if we wanted one.

bob
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: MechAg94 on February 17, 2022, 02:04:47 PM
I assume they had a way of determining which grenades had the wrong fuse?
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: BobR on February 17, 2022, 02:38:54 PM
I assume they had a way of determining which grenades had the wrong fuse?

The way he explained it was they would put them where they was a very high probability of theft and just left them there. If they found any while they were out and about they just destroyed them all. The only way to find them was to pull the pin and let em rip. I just figured they had a way to deal with things, they didn't seem to be as constrained as the French Army we interacted with.

bob
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: WLJ on February 17, 2022, 02:43:59 PM

(I also avoid milsurp ammo that comes from countries where I wouldn't drink the water, like India or Zimbabwe.)

Turkish mil surplus 8mm Mauser is considered to be loaded too hot for most semi autos. 
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: Bogie on February 17, 2022, 07:44:14 PM
If you load a .308 or a .30-06 with a heavy bullet, and a case-filling powder, you risk tearing up the action in a semi-auto that uses an op rod... .
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: WLJ on February 17, 2022, 07:48:02 PM
If you load a .308 or a .30-06 with a heavy bullet, and a case-filling powder, you risk tearing up the action in a semi-auto that uses an op rod... .

M1 Garands have that problem because of the dogleg bend in the rod. That was largely fixed in the M14
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: WLJ on February 24, 2022, 02:43:09 PM
Watched the video. The rifle stood up pretty well to some obvious overloads, but it reinforces my opinion expressed early in this thread NOT to fire questionable ammo from a gun show (or anywhere else) and if I ever get a .50 BMG rifle (which I think is unlikely) to avoid Serbu. I think some other designs have likely failure modes that may not be quite as catastrophic to the shooter as that rifle.



Heeee's back
This time with a round loaded to the level that took out the Serbu in a Barrett.

I Blew Up My Barrett 50 Cal...For Science
https://www.youtube.com/watch?v=xRufSjBtJNE






Spoiler: It didn't do much better
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: Bogie on February 24, 2022, 06:02:17 PM
I suspect that my 180 grain 600 yard .308 rounds wouldn't be a happy combo, even in an M14... They were loaded pretty hot, but then again, I was playing at the time with custom actions, and we took a LONG time building up loads for that rifle... I really miss it. The primers were flowing a little, but weren't perfing...
 
FWIW, many benchrest competitors will run about 3420 fps with a 68 grain 6mm bullet - that's a known sweet spot/starting spot for working loads... You change the vibrational characteristics after that with seating depth. And yeah, we were starting with a touching the lands - not jammed... Jammed, if you have to pull your bolt with a life round, you can dump powder into your trigger, and that'll screw up your record target. Jammed does tend to do well, because it is consistent, but... Too much hassle.
 
And yeah - that is WAY over SAAMI for a 6PPC, but we were using custom actions and barrels...
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: Brad Johnson on February 25, 2022, 10:23:13 AM
We used to have a guy that sold home-rolled ammo at local gun shows. He stopped showing up after a bunch of folks experienced multiple squibs per box, some ending up with bulged barrels. Never had an overpressure that I know of, but his attention to detail with regard to powder drop was certainly lacking.

I saw a muzzle loader go boom at the range once due to straight up dumbassery. Guy was one of those "Why this here's modern gun steel, cain't hurt it fer nuthin. Don't matter much whut ya put in it" types that exist mostly to waste oxygen and employee's time at gun counters. I guess he figured powder meant for handgun loads meant it was powder with less power. Exactly one charge of Blue Dot later, he found out different. No one hurt that I recall, but lots of swearing and an invitation to never return.

Brad
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: K Frame on February 25, 2022, 10:37:08 AM
Really surprised that the bolt lugs didn't shear off the Barrett bolt.

That opening sequence was pretty funny, too.
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: dogmush on February 25, 2022, 10:43:47 AM
Looks like a pretty solid chunk of trunnion came at the camera at high speed.  That looks like it could do some damage.
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: HankB on February 25, 2022, 11:35:19 AM
Ouch - that Barrett isn't a gun I'd want to fire - or be close to when someone else was firing it - during a blow-up any more than that Serbu. (This makes me think back to one of those TV shooting shows where they welded back together a demilled 20mm cannon - Solothurn, Lahti, something like that. Then took it out and shot it.  They got away with it, but still . . . :facepalm: )

Only gun blow-up I sort of witnessed was a 12 gauge Browning Citori O/U. Match was going on at a trap field, we heard bang . . . bang . . . bang . . . BOOM!

Blew up at the breech. The barrels (minus parts at the chamber end) were rotated downward around the hinge pin around 135 degrees, and the sides of the receiver were bulged out. The gun was thoroughly destroyed, but the shooter suffered only some minor scratches to his arms and face; his shooting glasses picked up a few scratches, too, but they did their job and saved his eyes from any injury.

I don't think the guy ever did figure out what happened. As one of the more experienced shooters said, from what he'd seen over many formal shotgunning events, even a DOUBLE charge of shotgun powder should not have destroyed the gun that thoroughly. (I think the guy ultimately got some sort of compensation from Browning, but I'm not sure about that.)
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: WLJ on March 31, 2022, 07:30:37 PM
Guess he likes to blow up guns now
Rem 783 in 300 WinMag
BTW: As a fellow Kentuckian I wish to apologize on behalf of the state for that scope mount. 

Bolt Action Rifle EXPLOSION !!! (When Guns Go Boom - EP 2)
https://www.youtube.com/watch?v=PHNbDEoldqc
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: Boomhauer on March 31, 2022, 09:39:10 PM
Ouch - that Barrett isn't a gun I'd want to fire - or be close to when someone else was firing it - during a blow-up any more than that Serbu. (This makes me think back to one of those TV shooting shows where they welded back together a demilled 20mm cannon - Solothurn, Lahti, something like that. Then took it out and shot it.  They got away with it, but still . . . :facepalm: )

Only gun blow-up I sort of witnessed was a 12 gauge Browning Citori O/U. Match was going on at a trap field, we heard bang . . . bang . . . bang . . . BOOM!

Blew up at the breech. The barrels (minus parts at the chamber end) were rotated downward around the hinge pin around 135 degrees, and the sides of the receiver were bulged out. The gun was thoroughly destroyed, but the shooter suffered only some minor scratches to his arms and face; his shooting glasses picked up a few scratches, too, but they did their job and saved his eyes from any injury.

I don't think the guy ever did figure out what happened. As one of the more experienced shooters said, from what he'd seen over many formal shotgunning events, even a DOUBLE charge of shotgun powder should not have destroyed the gun that thoroughly. (I think the guy ultimately got some sort of compensation from Browning, but I'm not sure about that.)

During the Obama years I was at a carbine match where a shooter blew up a high dollar AR using a cheap near unknown brand of shitty ammo called USA Ammo.
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: WLJ on March 31, 2022, 09:47:05 PM
During the Obama years I was at a carbine match where a shooter blew up a high dollar AR using a cheap near unknown brand of shitty ammo called USA Ammo.

If you're thinking AMERC I remember them back then. The most absolutely crapyest ammo imaginable.
Just did a quick google search and it's hard to find anything on them now but I remember tests where one round was too weak to cycle the action the next was over pressured. Brittle cases, bullets seated too deep, crap powder, you name it.
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: HankB on March 31, 2022, 10:35:22 PM
If you're thinking AMERC I remember them back then. The most absolutely crapyest ammo imaginable.
Just did a quick google search and it's hard to find anything on them now but I remember tests where one round was too weak to cycle the action the next was over pressured. Brittle cases, bullets seated too deep, crap powder, you name it.
Sounds like Indian milsurp.
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: MechAg94 on March 31, 2022, 11:04:27 PM
Sounds like Indian milsurp.
https://www.youtube.com/watch?v=RoveJ1oNhSM
Speaking of Indian ammo, SmallArmsSolutions reviewed some Indian military ammo recently.  He said it chronographed good, but he mentioned hard primers.
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: Pb on April 01, 2022, 10:31:51 AM
https://www.youtube.com/watch?v=RoveJ1oNhSM
Speaking of Indian ammo, SmallArmsSolutions reviewed some Indian military ammo recently.  He said it chronographed good, but he mentioned hard primers.

It is hard to believe India can make anything firearms related that isn't crap.  They can't even make an AK rifle that functions properly.  Their military procurement news is always funny.
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: K Frame on April 01, 2022, 11:01:27 AM
The only Indian military surplus I've shot was cordite-loaded .303 from the 1960s, and it was fine.
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: HankB on April 01, 2022, 03:55:20 PM
A general rule of thumb is not to fire ammo that comes from a country where you wouldn't drink the water.

I may bend the rule a little if the gun also came from the same country, e.g, Russian ammo in a Mosin-Nagant, Chinese ammo in a Polytech or Norinco rifle, etc.
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: WLJ on May 12, 2022, 10:21:40 PM
But wait, there's more

Glock 19 EXPLOSION !!! (When Guns Go Boom - EP 3)
https://www.youtube.com/watch?v=GFF1-ry-_Tc
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: HeroHog on May 13, 2022, 11:19:03 PM
(https://armedpolitesociety.com/proxy.php?request=http%3A%2F%2Fherohog.com%2Fimages%2Fguns%2Fhowglockworks.gif&hash=f52dc374e1ea5056ad31902d3b1b873672bcf72c)
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: Fly320s on May 14, 2022, 05:53:47 AM
But wait, there's more

Glock 19 EXPLOSION !!! (When Guns Go Boom - EP 3)
https://www.youtube.com/watch?v=GFF1-ry-_Tc

Next, he will drop Sig 320s to see if they fire.
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: K Frame on May 14, 2022, 06:47:34 AM
400,000 PSI?

WTF did he have in there?

I don't think even EC Flash Powder would generate those kinds of chamber pressures.

And does he remind anyone of Merle from The Walking Dead?
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: WLJ on September 05, 2022, 12:35:50 PM
Mark Serbu responding to criticism of his gun

I haven't watched the whole thing yet due to time constraints

RN-50 Blow-up Analysis: UPDATE!
https://www.youtube.com/watch?v=h8-eVoy38go
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: Hawkmoon on September 05, 2022, 12:54:10 PM
I had never heard of Mark Serbu before the Kentucky Ballistics kaboom, and I have never had any interest in .50 BMG rifles. With that as background ... in my humble opinion Mark Serbu needs to stop making YouTube videos. Everything I have seen from him since the incident comes across as whiny, self-serving, overly defensive claptrap.
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: HankB on September 06, 2022, 08:38:17 AM
With the money Kentucky Ballistics apparently has to buy guns and then just blow them up, it would be more useful to get a bunch of different rifles (Winchester, Remington, Savage, Browning, Weatherby, etc.) chambered for the same cartridge, and feed them gradually increasing overloads until they start taking damage - increasing headspace, ruptured case heads, etc.

P.O.Ackley did this decades ago, mostly with military actions. (Surprising many, early Jap Arisakas were among the strongest.) It's time for a repeat with "modern" rifles - the gun rags won't do this because of fear of advertising dollars going away.
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: WLJ on September 12, 2022, 05:41:48 PM
Time to blow up a Desert Eagle

My Desert Eagle EXPLODED !!! (When Guns Go Boom – EP 5)
https://www.youtube.com/watch?v=3-PjBmw19uM
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: Pb on September 12, 2022, 11:02:26 PM
I hate it when people destroy guns without a good reason. 
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: Hawkmoon on September 12, 2022, 11:15:20 PM
It's hard to believe that this guy has almost 3 million subscribers.
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: bedlamite on September 13, 2022, 04:57:06 AM
https://m.youtube.com/watch?v=4REiTR2dx98
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: dogmush on September 13, 2022, 08:02:17 AM
I hate it when people destroy guns without a good reason.

Around $300k-$400k a year is a pretty damn good reason.
Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: WLJ on September 13, 2022, 10:01:45 AM
Mark Serbu again
Says the round had pistol powder loaded
Lots of rambling in the video. I zoned out part way in. Honestly I'm started to not care anymore

RN 50 Blow Up...CONCLUSION!
https://www.youtube.com/watch?v=4REiTR2dx98


Title: Re: Kentucky Ballistics - My 50 Cal Exploded
Post by: WLJ on April 05, 2024, 11:59:45 AM
Kel-Tec RFB (308 bullpup) vs a round est to be ~300k psi (according to KB) with a squib thrown in for good measure.
From the thumbnail I thought he was going to blow up a AUG

Are Bullpup Rifles Safe ??? (When Guns Go Boom EP – 11)
https://www.youtube.com/watch?v=pWxPEO3uV2g

Spoiler alert
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It held up surprisingly well
I mean your arm may be cut up but your face would be okay.