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Posted: 5/2/2021 8:31:33 AM EDT
[#1]
Quote HistoryQuoted: You know you can put a bigger thread than needed and have less engagement, right? The design was probably based on the wall thickness around the chamber and not needing that size thread. Perhaps you can show the math that shows the number of threads was inadequate for the situation? Lemme guess, you'll avoid any actual numbers and go "BuT lOoK aT tHe PiCtuRe." I have faith that someone who can make the claims you can can show your work. Quote HistoryQuoted: Quoted: As several others in this thread have pointed out, the cap that threads over the barrel is a poor design. There is not enough thread engagement, you get peak strength at 1.5 x Diameter. On typical course threads that is in the ballpark of 8-12 full turns of engagement vs the 3-4 shown in pictures. Again as has been stated, 60 degree v threads should be torqued/stretched and not just hand tightened. loose threads are subject to shock loading that isn't evenly distributed, which can cause fatigue and failure/shearing. The most glaringly obvious problem with this design is the cap that threads Over the breach instead of Into the breach. - It looks like the cap has about a 1 1/4" inside diameter, it threads over the outside of the barrel and creates a pretty much airtight seal. - A normal 50 bmg is in the ballpark of 55ksi developing 20,000 lbs of bolt thrust (based on a 0.680" case I.D.), an 85ksi load would produce about 31,000 lbs of thrust which may or may not be enough to cause a failure in this gun. Not much safety factor but at least there is some. - What nobody seems to be taking into account is what happens in the event of a case rupture or even a pierced primer. All of that pressure is going to vent into that sealed up cap. That means that we now have 55,000+ psi pushing against the 1 1/4" diameter on the inside of the cap instead of the 0.680" diameter inside the case, generating at least 67,000 lbs of thrust. I would not be at all surprised if this is what caused the failure Kentucky Ballistics had. You know you can put a bigger thread than needed and have less engagement, right? The design was probably based on the wall thickness around the chamber and not needing that size thread. Perhaps you can show the math that shows the number of threads was inadequate for the situation? Lemme guess, you'll avoid any actual numbers and go "BuT lOoK aT tHe PiCtuRe." I have faith that someone who can make the claims you can can show your work. Did you both read and understand what he wrote? Per math stuff 4 threads of 1 1/4 - 7 would be about .4 sq in. Based on the previously posted bolt thrust numbers for intact case of 27k lbf and breached case of 67k lbf the steel was under stress of 75k psi or 167k psi, respectively, assuming perfect loading of the failed threads. Whatever happened, 4 threads just wasn’t enough to do the job. |
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Posted: 5/2/2021 8:49:55 AM EDT
[#2]
Seems like the gun would be perfectly fine if it weren't for suspect old kabooming ammunition. That is on the person not the tool. Lesson's learned, do not use suspect ammo, maybe a little better design would be safer in case of kabooms again (since people are going to be people) and do not use that type of ammo with a muzzle brake. Glad he is OK.
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Posted: 5/2/2021 9:02:00 AM EDT
[#3]
Quote HistoryQuoted: If I recall correctly, there is no SAAMI proof or operating pressure for .50BMG as it is not a "sporting" cartridge. If there is a proof pressure in the USA I could not find it with a basic search. FWIW, back in the late 90's I bought some 50BMG "Proof" rounds. If I recall correctly, they had the same powder/charge as a standard Ball load, but were loaded with a 1,000 grain projectile. The bullet looked like a long FMJ round nose similar to a Dangerous Game Solid. I'm sure I still have one around here somewhere. I have no idea what kind of pressure those rounds developed. Tony |
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Posted: 5/2/2021 10:24:28 AM EDT
[#4]
Quote HistoryQuoted: FWIW, back in the late 90's I bought some 50BMG "Proof" rounds. If I recall correctly, they had the same powder/charge as a standard Ball load, but were loaded with a 1,000 grain projectile. The bullet looked like a long FMJ round nose similar to a Dangerous Game Solid. I'm sure I still have one around here somewhere. I have no idea what kind of pressure those rounds developed. Tony Quote HistoryQuoted: Quoted: If I recall correctly, there is no SAAMI proof or operating pressure for .50BMG as it is not a "sporting" cartridge. If there is a proof pressure in the USA I could not find it with a basic search. FWIW, back in the late 90's I bought some 50BMG "Proof" rounds. If I recall correctly, they had the same powder/charge as a standard Ball load, but were loaded with a 1,000 grain projectile. The bullet looked like a long FMJ round nose similar to a Dangerous Game Solid. I'm sure I still have one around here somewhere. I have no idea what kind of pressure those rounds developed. Tony Tony, Thank you for that bit of "inane" information.  That should make for an interesting looking round and makes me wonder if it hits the lands when chambered. |
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Posted: 5/2/2021 10:42:14 AM EDT
[#5]
Quote HistoryQuoted: Tony, Thank you for that bit of "inane" information. That should make for an interesting looking round and makes me wonder if it hits the lands when chambered. Nothing inane about Tony's post, your attempts to appear as if you know what you're talking about however are. The M1 HPT proof load does indeed use a heaver bullet but also has 5gr more of WC 860 than M33 ball. https://www.survivalmonkey.com/00photo/50BMG.pdf |
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Posted: 5/2/2021 10:45:33 AM EDT
[#6]
Quote HistoryQuoted: That was never on my list. Quote HistoryQuoted: Quoted: Damn. Firing .50 SLAP mystery-meat rounds just got crossed off of my list. That was never on my list. Not firing anything like that in my $8k rifle. |
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Posted: 5/2/2021 2:20:48 PM EDT
[#7]
Quote HistoryQuoted: Nothing inane about Tony's post, your attempts to appear as if you know what you're talking about however are. The M1 HPT proof load does indeed use a heaver bullet but also has 5gr more of WC 860 than M33 ball. https://www.survivalmonkey.com/00photo/50BMG.pdf Quote HistoryQuoted: Quoted: Tony, Thank you for that bit of "inane" information. That should make for an interesting looking round and makes me wonder if it hits the lands when chambered. Nothing inane about Tony's post, your attempts to appear as if you know what you're talking about however are. The M1 HPT proof load does indeed use a heaver bullet but also has 5gr more of WC 860 than M33 ball. https://www.survivalmonkey.com/00photo/50BMG.pdf You should change your avatar. You're like an angry chihuahua tugging at a pant leg. None of the details or information I have discussed in this thread were first(or only) mentioned by myself. Yet you keep nipping at my ankle. I opened and have participated in this thread to learn. Your posts mostly distract from that, but you do you. |
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Posted: 5/2/2021 2:52:17 PM EDT
[#8]
Quote HistoryQuoted: You should change your avatar. You're like an angry chihuahua tugging at a pant leg. None of the details or information I have discussed in this thread were first(or only) mentioned by myself. Yet you keep nipping at my ankle. I opened and have participated in this thread to learn. Your posts mostly distract from that, but you do you. These late teen to twenty joins are aggravating, to say the least. |
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Posted: 5/2/2021 2:56:28 PM EDT
[#9]
 Why His 50 BMG Exploded ~ Rex Reviews |
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Posted: 5/2/2021 3:16:35 PM EDT
[#10]
Quote HistoryQuoted: 100% on the same page, I just wanted to point out that it is an inherently flawed and dangerous design in this case. As you pointed out the failure mode for all of those weapons is fairly safe. if the barrel/trunnion Thread fails in an m2/Ar/Bolt gun, the barrel plops to the ground infront of the gun and the user is not likely to have any life threatening injuries, or the force is contained/absorbed inside of thee receiver. The problem with the RN50 is there isn't a great way to vent gas and there is no receiver to protect the shooter. Its kind of a head scratcher as to how it made it into production. The best bet to fix it might be to add an intermediate trunnion, thread the barrel into it and make the barrel threads the weak point instead of the breach threads. That way when it fails, it fails away from your face. Quote HistoryQuoted: Quoted: Agree about the trapping of the gas with a cap design. That bolt thrust basically quadruples in the event of a rupture since the area quadruples with a 2x increase of the bore of your "piston". However there's nothing wrong with threads over the breach as long as it is sufficiently thick to decouple the hoop stress from the shear stress, provides a bleed path for gases in the event of a rupture, and you have sufficient mass/obstruction to protect the shooter in the event of a KB. Not much different than many rifle barrels including ARs, many bolt actions, etc... Here is the RN50 vs M2 https://cdn11.bigcommerce.com/s-dmbfmt5mav/images/stencil/900x1800/products/116/446/RN0025_1__72217.1604005225.jpg?c=2https://www.practicalmachinist.com/vb/attachments/f24/52000d1336761626-fs-m2hb-50cal-barrel-50cal-bbl-chamber.jpg 100% on the same page, I just wanted to point out that it is an inherently flawed and dangerous design in this case. As you pointed out the failure mode for all of those weapons is fairly safe. if the barrel/trunnion Thread fails in an m2/Ar/Bolt gun, the barrel plops to the ground infront of the gun and the user is not likely to have any life threatening injuries, or the force is contained/absorbed inside of thee receiver. The problem with the RN50 is there isn't a great way to vent gas and there is no receiver to protect the shooter. Its kind of a head scratcher as to how it made it into production. The best bet to fix it might be to add an intermediate trunnion, thread the barrel into it and make the barrel threads the weak point instead of the breach threads. That way when it fails, it fails away from your face. Trash Panda corrected me about the M2 I had forgotten about the lock plate that the cam pushes up to hold the bolt in place on an M2. From a design standpoint this could be kept the same. However, instead of the dog ears behind the cap make it a tilting block that has a raceway cut into the receiver. When the barrel tilts down to load the block falls. When the barrel tilts to lock it can engage a lever to push the block back up. Like low/high wall falling block only the barrel is the lever. It’s two fold; won’t sheer like those dog ears and two prevents the gun from firing out of battery. Add a striker through it if you must. It will likely lengthen the receiver by a half inch, if at all |
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Posted: 5/2/2021 3:23:30 PM EDT
[#11]
Quote HistoryQuoted: FWIW, back in the late 90's I bought some 50BMG "Proof" rounds. If I recall correctly, they had the same powder/charge as a standard Ball load, but were loaded with a 1,000 grain projectile. The bullet looked like a long FMJ round nose similar to a Dangerous Game Solid. I'm sure I still have one around here somewhere. I have no idea what kind of pressure those rounds developed. Tony We used those 1000 grain proof loads at Barrett. I believe the proof pressure was around 80,000 psi. Standard .50bmg is around 55,000-56,000 psi. The proof loads were 30% over standard chamber pressure. |
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Posted: 5/2/2021 3:31:24 PM EDT
[#12]
Quote HistoryI watched until he made a statement that demonstrated he clearly does not understand the difference between CUP(Copper Units of Pressure) and PSI. He had already made some errors, but that was when I gave up on his video. Approx. 10:30 mark. |
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Posted: 5/2/2021 5:24:42 PM EDT
[#13]
When I was in the Marine Corps we were shooting the M2 machine guns.
One of the rounds was a hang fire. Guy did a failure to fire drill and it went off as he opened the breech. He got a big multiple stitches wound from it at the Naval Hospital. It was some old ammunition that they gave us for training. Once he had that huge fireball from the first Slap round he should have stopped. It can happen with any gun. Those SLAP rounds were loaded with god knows what and were way way over a proof round. He is indeed a lucky man. |
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Posted: 5/2/2021 5:59:31 PM EDT
[#14]
Quote HistoryQuoted: I watched until he made a statement that demonstrated he clearly does not understand the difference between CUP(Copper Units of Pressure) and PSI. Also, the copper crusher method is completely outdated for measuring chamber pressures anyway, modern proofing is done with piezoelectric transducers that are reusable. His whole theory is bonkers anyway. An obstructed muzzle brake will crack or eject the brake, not the breech. When the projo reaches the brake, the chamber pressure will already be tens of percents below max pressure, which actually occurs only a very short time after the bullet exits the casing. There is no physical way for the pressure to increase over the previous max pressure even if the bullet was entirely caught in the brake and formed a total occlusion there. While there may be a small fraction of unburnt powder at that point, the volume of the sealed pressure vessel is going to be many times the volume at max pressure. There is not enough powder, not enough reaction mass. It's an entirely impossible theory to begin with. If the sabot causes a barrel obstruction that can lead to unsafe pressures, it has to happen way closer to the chamber. If the bullet has reached the brake, the brake or muzzle end of the barrel may fail, but not the breech that is way heavier and built to withstand higher pressures (max chamber pressure vs. muzzle pressure). |
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Posted: 5/2/2021 6:10:29 PM EDT
[#15]
How much pressure does it take for a 350gr bullet to produce enough recoil energy to operate the M2 machine gun?
Spoiler alert....it sure as shit is not 55k. Tony |
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Posted: 5/2/2021 7:21:20 PM EDT
[#16]
Quote HistoryQuoted: If anyone is selling one cheap, let me know. Edit. Details about the weapon here. Not a typical RN50. This was ammo related, similar to what happened in Takata airbags.  https://www.youtube.com/watch?v=tpp4SdE1MUkYeah that's interesting, time stamped link to 5:08 https://youtu.be/tpp4SdE1MUk?t=308 He mentions that he's aware SLAP can't be fired from most .50's but Serbu sent him a heavy barreled version of the RN50 with a "machine gun chamber." For people talking about the big muzzle flash, something similar happened on Demolition Ranch with a suppressed Barrett .50 in a recent video and caused a baffle strike. See the below time stamped link. https://youtu.be/iqLMU35qpgg?t=553 |
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Posted: 5/2/2021 7:58:14 PM EDT
[#17]
The round in the video that he shows lacks the crimp around the sabot and it has visible setback in the case compared to previous Slap rounds he fired.
Just wondering if somewhere along the way someone took some sabots and projectiles that were surplused, threw a random powder into it and seated the bullet as a display round and maybe later passed away or sold it as a collector round and then it got into circulation, where he bought it with the intent to shoot it. Watched a few of his videos on SLAP rounds he did before, none of them ever had a muzzle flash comparable to the one shown two rounds before the gun let go. |
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Posted: 5/2/2021 8:07:46 PM EDT
[#18]
Quote HistoryQuoted: Also, the copper crusher method is completely outdated for measuring chamber pressures anyway, modern proofing is done with piezoelectric transducers that are reusable. His whole theory is bonkers anyway. An obstructed muzzle brake will crack or eject the brake, not the breech. When the projo reaches the brake, the chamber pressure will already be tens of percents below max pressure, which actually occurs only a very short time after the bullet exits the casing. There is no physical way for the pressure to increase over the previous max pressure even if the bullet was entirely caught in the brake and formed a total occlusion there. While there may be a small fraction of unburnt powder at that point, the volume of the sealed pressure vessel is going to be many times the volume at max pressure. There is not enough powder, not enough reaction mass. It's an entirely impossible theory to begin with. If the sabot causes a barrel obstruction that can lead to unsafe pressures, it has to happen way closer to the chamber. If the bullet has reached the brake, the brake or muzzle end of the barrel may fail, but not the breech that is way heavier and built to withstand higher pressures (max chamber pressure vs. muzzle pressure). Quote HistoryQuoted: Quoted: I watched until he made a statement that demonstrated he clearly does not understand the difference between CUP(Copper Units of Pressure) and PSI. Also, the copper crusher method is completely outdated for measuring chamber pressures anyway, modern proofing is done with piezoelectric transducers that are reusable. His whole theory is bonkers anyway. An obstructed muzzle brake will crack or eject the brake, not the breech. When the projo reaches the brake, the chamber pressure will already be tens of percents below max pressure, which actually occurs only a very short time after the bullet exits the casing. There is no physical way for the pressure to increase over the previous max pressure even if the bullet was entirely caught in the brake and formed a total occlusion there. While there may be a small fraction of unburnt powder at that point, the volume of the sealed pressure vessel is going to be many times the volume at max pressure. There is not enough powder, not enough reaction mass. It's an entirely impossible theory to begin with. If the sabot causes a barrel obstruction that can lead to unsafe pressures, it has to happen way closer to the chamber. If the bullet has reached the brake, the brake or muzzle end of the barrel may fail, but not the breech that is way heavier and built to withstand higher pressures (max chamber pressure vs. muzzle pressure). Pretty much everything you wrote is what I was thinking, but didn't write out to avoid conflict the aggressive chihuahua.
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Posted: 5/2/2021 9:22:59 PM EDT
[#19]
Quote HistoryQuoted: Yeah that's interesting, time stamped link to 5:08 https://youtu.be/tpp4SdE1MUk?t=308 He mentions that he's aware SLAP can't be fired from most .50's but Serbu sent him a heavy barreled version of the RN50 with a "machine gun chamber." For people talking about the big muzzle flash, something similar happened on Demolition Ranch with a suppressed Barrett .50 in a recent video and caused a baffle strike. See the below time stamped link. https://youtu.be/iqLMU35qpgg?t=553 Blue Tip Warning |
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Posted: 5/3/2021 12:26:12 AM EDT
[#20]
Quote HistoryQuoted: You should change your avatar. You're like an angry chihuahua tugging at a pant leg. None of the details or information I have discussed in this thread were first(or only) mentioned by myself. Yet you keep nipping at my ankle. I opened and have participated in this thread to learn. Your posts mostly distract from that, but you do you.  , that's ok. Lots of people have trouble admitting they're wrong. Mostly people under the age of 17. No you weren't the first, but that's not an excuse. ziarifleman was the first to assert that proof pressure was at 85ksi, I stated it's 65ksi, you tried to "correct" me that it's not true it's actually 67ksi  , I showed from the Army technical manual that it's 65ksi. Now you're butthurt that people are citing facts and correcting you. It's like debating with a liberal.
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Posted: 5/3/2021 1:30:29 AM EDT
[#21]
Quote HistoryNot really a good watch. 30 minutes long to discuss a theory that I don't really believe at all. This pretty much always happens when a poster just posts a link to a video with no commentary or summary. It almost always sucks. |
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Posted: 5/3/2021 5:04:34 AM EDT
[#22]
Quote HistoryQuoted: Agree about the trapping of the gas with a cap design. That bolt thrust basically quadruples in the event of a rupture since the area quadruples with a 2x increase of the bore of your "piston". However there's nothing wrong with threads over the breach as long as it is sufficiently thick to decouple the hoop stress from the shear stress, and provides a bleed path for gases in the event of a rupture. Not much different than many rifle barrels including ARs, many bolt actions, etc... Here is the RN50 vs M2 https://cdn11.bigcommerce.com/s-dmbfmt5mav/images/stencil/900x1800/products/116/446/RN0025_1__72217.1604005225.jpg?c=2https://www.practicalmachinist.com/vb/attachments/f24/52000d1336761626-fs-m2hb-50cal-barrel-50cal-bbl-chamber.jpg Also people keep talking about preload on the threads but it is simply not the issue. There is ZERO preload on a M2 barrel which has much more coarse threads and are often beat to shit. You freely turn it to headspace the gun but I've never heard of a barrel being stripped from the M2 barrel extension. However the gases aren't trapped like with a cap design. Quote HistoryQuoted: Quoted: As several others in this thread have pointed out, the cap that threads over the barrel is a poor design. There is not enough thread engagement, you get peak strength at 1.5 x Diameter. On typical course threads that is in the ballpark of 8-12 full turns of engagement vs the 3-4 shown in pictures. Again as has been stated, 60 degree v threads should be torqued/stretched and not just hand tightened. loose threads are subject to shock loading that isn't evenly distributed, which can cause fatigue and failure/shearing. The most glaringly obvious problem with this design is the cap that threads Over the breach instead of Into the breach. - It looks like the cap has about a 1 1/4" inside diameter, it threads over the outside of the barrel and creates a pretty much airtight seal. - A normal 50 bmg is in the ballpark of 55ksi developing 20,000 lbs of bolt thrust (based on a 0.680" case I.D.), an 85ksi load would produce about 31,000 lbs of thrust which may or may not be enough to cause a failure in this gun. Not much safety factor but at least there is some. - What nobody seems to be taking into account is what happens in the event of a case rupture or even a pierced primer. All of that pressure is going to vent into that sealed up cap. That means that we now have 55,000+ psi pushing against the 1 1/4" diameter on the inside of the cap instead of the 0.680" diameter inside the case, generating at least 67,000 lbs of thrust. I would not be at all surprised if this is what caused the failure Kentucky Ballistics had. Agree about the trapping of the gas with a cap design. That bolt thrust basically quadruples in the event of a rupture since the area quadruples with a 2x increase of the bore of your "piston". However there's nothing wrong with threads over the breach as long as it is sufficiently thick to decouple the hoop stress from the shear stress, and provides a bleed path for gases in the event of a rupture. Not much different than many rifle barrels including ARs, many bolt actions, etc... Here is the RN50 vs M2 https://cdn11.bigcommerce.com/s-dmbfmt5mav/images/stencil/900x1800/products/116/446/RN0025_1__72217.1604005225.jpg?c=2https://www.practicalmachinist.com/vb/attachments/f24/52000d1336761626-fs-m2hb-50cal-barrel-50cal-bbl-chamber.jpg Also people keep talking about preload on the threads but it is simply not the issue. There is ZERO preload on a M2 barrel which has much more coarse threads and are often beat to shit. You freely turn it to headspace the gun but I've never heard of a barrel being stripped from the M2 barrel extension. However the gases aren't trapped like with a cap design. I have. And it involved shooting SLAP rounds late in a day of shooting. |
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Posted: 5/3/2021 5:50:22 AM EDT
[#23]
Watched the whole thing.
Yeah... I wouldn't shoot that thing. I've shot enough to have a couple catastrophic ammunition failures, thankfully of things much smaller than .50 BMG, and I've imagined several times how much it would suck if something huge like a .50 detonated on me. What happened to him is pretty much how I imagined it. Would only shoot something that is going to eat a lot more of the catastrophic failure than a couple little metal ears. |
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Posted: 5/3/2021 6:36:12 AM EDT
[#24]
Quote HistoryQuoted: Watched the whole thing. Yeah... I wouldn't shoot that thing. I've shot enough to have a couple catastrophic ammunition failures, thankfully of things much smaller than .50 BMG, and I've imagined several times how much it would suck if something huge like a .50 detonated on me. What happened to him is pretty much how I imagined it. Would only shoot something that is going to eat a lot more of the catastrophic failure than a couple little metal ears. Seriously. That thing is mickey mouse engineering at best |
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Posted: 5/3/2021 8:14:15 AM EDT
[#25]
Well
After reading all 9 pages of arfcom shit posting as typical. And yes i watched the vid same day it was posted on U tube. I will say. I have mixed feeling on this kid. 1st respect for not blaming Serbu for his mistake. 2nd for not sueing Serbu for his mistake. Takes a real person to admit that type of wrong & stupidity. Where I lose a lot of that respect is his willingness to keep shooting the gun after he mentions there are issues. And not being sure about the ammo. I recently passed on roufuss ammo with x-rays Why? The simple reason i wasn't there when the x-rays were taken. How does anyone prove those 3 rounds i was going to buy were the ones in the x-ray. Yes I have a 50 bmg like others here and yes i have time on the M2 the Barret & ar50 ( my 1st 50) And currently have a 5 shot bolt gun. Like anything that goes boom it requires a certain sense of situational awareness. IE: gun doesn't sound right, shoot right, or have consistent muzzle blast you need to CHECK YER SELF BECORE YOU WRECK YOUR SELF. As the young kid found out the hard way. Inattention and stupidity hurt. And it should, one thing i know is he will NOT make that mistake again. I'm glad he made it to tell the tale and has a good out look on life. Off to buy a thumb shirt now. |
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Posted: 5/3/2021 8:22:10 AM EDT
[#26]
Quote HistoryQuoted: , that's ok. Lots of people have trouble admitting they're wrong. Mostly people under the age of 17. No you weren't the first, but that's not an excuse. ziarifleman was the first to assert that proof pressure was at 85ksi, I stated it's 65ksi, you tried to "correct" me that it's not true it's actually 67ksi , I showed from the Army technical manual that it's 65ksi. Now you're butthurt that people are citing facts and correcting you. It's like debating with a liberal.It is a good thing that these are an old pair of pants as you are shredding the cuffs. It isn't always about you..., no "correction" involved. I included and explained the math and just posted the higher value. Two proof pressures had been stated in the thread, so I went looking for primary sources. Then shared what I found. You did not post the technical manual until after my post. Again, it isn't always about you. |
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Posted: 5/3/2021 9:34:21 AM EDT
[#27]
Quote HistoryQuoted: It is a good thing that these are an old pair of pants as you are shredding the cuffs. It isn't always about you..., no "correction" involved. I included and explained the math and just posted the higher value. Two proof pressures had been stated in the thread, so I went looking for primary sources. Then shared what I found. You did not post the technical manual until after my post. Again, it isn't always about you. LOL, ankle biting is when someone says "akshually, it's not 65 it's 67!!"". I sent you a google link because you said you couldn't find the pressures from your research. The search clearly (or rather it would be clear to most people) returns multiple sources citing 65 as the proof pressure, and the Tech Manual is cited if you have the handful of IQ points required to find it as the primary source in the reference section. 
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Posted: 5/3/2021 11:09:11 AM EDT
[#28]
Quote HistoryQuoted: LOL, ankle biting is when someone says "akshually, it's not 65 it's 67!!"". I sent you a google link because you said you couldn't find the pressures from your research. The search clearly (or rather it would be clear to most people) returns multiple sources citing 65 as the proof pressure, and the Tech Manual is cited if you have the handful of IQ points required to find it as the primary source in the reference section. I'm going to be wearing capri pants before long. You must be a hoot at parties. I don't "click" anyone, as you did provide some useful information but I am done with the annoyance. Vaya con Dios! |
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Posted: 5/3/2021 4:03:31 PM EDT
[#29]
So no one ever answered my question about what bounced off the table at ~ 3:16 in the video when he locks the action shut. Right before the Kaboom.
Maybe a piece that had cracked off from previous rounds? |
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Posted: 5/3/2021 4:13:09 PM EDT
[#30]
Quote HistoryQuoted: So no one ever answered my question about what bounced off the table at ~ 3:16 in the video when he locks the action shut. Right before the Kaboom. Maybe a piece that had cracked off from previous rounds? You can see it enter frame from the right (and below the level of the table top) immediately before he closes the action... really helps to slow down the video if you cant see it. |
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Posted: 5/3/2021 6:14:53 PM EDT
[#31]
Quote HistoryQuoted: its a moth/butterfly flying in the background. You can see it enter frame from the right (and below the level of the table top) immediately before he closes the action... really helps to slow down the video if you cant see it. Quote HistoryQuoted: Quoted: So no one ever answered my question about what bounced off the table at ~ 3:16 in the video when he locks the action shut. Right before the Kaboom. Maybe a piece that had cracked off from previous rounds? You can see it enter frame from the right (and below the level of the table top) immediately before he closes the action... really helps to slow down the video if you cant see it. LOL, Man, you're right. I'd slowed it down before, but never looked below the table top. It pops up just as the action clicks shut and gives the illusion that something sproinged off the gun. |
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Posted: 5/4/2021 1:44:27 PM EDT
[#32]
Quote HistoryQuoted: I remember 10? 15? (or more) years ago seeing pics of a barret opened up like a scissor jack. Want to say the bolt exited the receiver and crumpled the shooters jaw...but it has been a while. I don't know the circumstances that caused it, nor the injuries sustained, but this is likely the incident you are describing;  
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Posted: 5/4/2021 2:20:53 PM EDT
[#33]
Quote HistoryQuoted: I don't know the circumstances that caused it, nor the injuries sustained, but this is likely the incident you are describing; https://i.imgur.com/Zs8Swbq.jpg https://i.imgur.com/ycLfFOs.jpg That was from a round jammed with the carrier partially open. Someone tried to kick the action closed while the shooter was still behind the rifle. Extractor launched out the side and impeded in a soldiers cheek. Ammo was old WW2 AP |
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Posted: 5/4/2021 2:24:13 PM EDT
[#34]
I'm at work so I can't link the video right now, but Mark Serbu made a youtube video sort of addressing the incident.
In the future he plans to try and explain exactly what happened and will "destroy" some guns to see if he can replicate the failure. I'm pretty excited for that. |
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Posted: 5/4/2021 5:24:49 PM EDT
[#35]
 RN-50 Blow-Up |
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Posted: 5/4/2021 5:27:04 PM EDT
[#36]
There is also this video which is followed by this comment:
markserbu Excellent analysis! You picked up on some very esoteric details....we should talk.  My take on Kentucky Ballistics' Accident |
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Posted: 5/4/2021 6:43:05 PM EDT
[#37]
I Haven't seen this question asked yet or mention of it (which is shocking because nothing gets missed here typically).
Around the 3:18 mark when he closes the action something goes skipping forward across the table. Does anyone know what that was? I didn't even notice it but a friend asked me. ETA nevermind it appears to be a moth in the background. Just watched it on a larger screen. You can see the moth come in behind him and then up like it bounced off the table. |
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Posted: 5/4/2021 6:49:56 PM EDT
[#38]
Quote HistoryQuoted: I Haven't seen this question asked yet or mention of it (which is shocking because nothing gets missed here typically). Around the 3:18 mark when he closes the action something goes skipping forward across the table. Does anyone know what that was? I didn't even notice it but a friend asked me. ETA nevermind it appears to be a moth in the background Look 7 posts above yours. |
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Posted: 5/4/2021 6:51:57 PM EDT
[#39]
Quote HistoryQuoted: Look 7 posts above yours. Quote HistoryQuoted: Quoted: I Haven't seen this question asked yet or mention of it (which is shocking because nothing gets missed here typically). Around the 3:18 mark when he closes the action something goes skipping forward across the table. Does anyone know what that was? I didn't even notice it but a friend asked me. ETA nevermind it appears to be a moth in the background Look 7 posts above yours. Yeah.....I'm a dumbass
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Posted: 5/4/2021 6:57:25 PM EDT
[#40]
Quote HistorySeems to be pretty damn honest and above board..hope he gets it figured out... |
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Posted: 5/4/2021 6:57:48 PM EDT
[#41]
It's interesting, if you check his youtube channel. In the video right before the kaboom video, he was "torture testing" the same gun by filling it up with sand, mud, gravel, and other debris. Not saying it's related to the failure but my first thought was, 'that gun is going to blow up'. Then his channel went dark and the very next video he posted was the kaboom.
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Posted: 5/4/2021 7:00:43 PM EDT
[#42]
Quote HistoryQuoted: It's interesting, if you check his youtube channel. In the video right before the kaboom video, he was "torture testing" the same gun by filling it up with sand, mud, gravel, and other debris. Not saying it's related to the failure but my first thought was, 'that gun is going to blow up'. Then his channel went dark and the very next video he posted was the kaboom. Wrong.gif That was a Barrett 50 cal in the previous video. |
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Posted: 5/4/2021 7:50:17 PM EDT
[#43]
Quote HistoryQuoted: There is also this video which is followed by this comment: https://www.youtube.com/watch?v=bBNHI1_urWsThis guy's video is EXACTLY what I think happened. the case/primer failed and the cap went from being a clamping force on the case to being a pressure vessel. it didn't like that. |
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Posted: 5/4/2021 8:20:40 PM EDT
[#44]
n o p e
nvm |
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Posted: 5/4/2021 9:26:04 PM EDT
[#45]
Quote HistoryQuoted: That was from a round jammed with the carrier partially open. Someone tried to kick the action closed while the shooter was still behind the rifle. Extractor launched out the side and impeded in a soldiers cheek. Ammo was old WW2 AP I think you are confusing it with the BOHICA KB. There the shooter tried to force close the bolt and it KB'd. The KB Barrett was from a hangfire in Honduras where the shooter pulled back the bolt after the click...... then it went bang: https://www.arrse.co.uk/community/threads/barrett-50bmg-kaboom.107041/ |
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Posted: 5/4/2021 9:40:47 PM EDT
[#46]
Quote HistoryQuoted: Realistically as long as the threads are not of some horrible tolerance or the steel too brittle when the pressure is applied the threads will deform and begin to distribute the load across them. I wasn't going to comment unless someone mentioned thread tolerance. I sold my RN50 because I never could have peace of mind with it. The cap wobbled too much for me. I seriously think lug nuts may have better tolerance. I contacted Mark with measurements to see if it was defective. I laid a .10mm feeler gauge on the left side of the barrel face and while tilting the cap by hand toward the gauge side, screwed the cap on till it just touched the gauge. Then without turning the cap, I tilted the cap toward the other side and was able to insert a .70mm gauge in the gap created. So, a .6mm wobble in the cap. If the cap was just cracked loose, you could even notice slack front to rear. Mark replied that "Yes, sometimes the breech cap threads can seem loose, but they're fine I assure you." I fired it a few times, but eventually sold it and got something else due to the slack threads and the unnecessarily high scope rail. |
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Posted: 5/4/2021 10:22:31 PM EDT
[#47]
Quote HistoryQuoted: I contacted Mark with measurements to see if it was defective. I laid a .10mm feeler gauge on the left side of the barrel face and while tilting the cap by hand toward the gauge side, screwed the cap on till it just touched the gauge. Then without turning the cap, I tilted the cap toward the other side and was able to insert a .70mm gauge in the gap created. So, a .6mm wobble in the cap. If the cap was just cracked loose, you could even notice slack front to rear. Mark replied that "Yes, sometimes the breech cap threads can seem loose, but they're fine I assure you." Damn, if there was any play, that would act like a hammer. Try "hitting" something, with your hand resting on a table, then compare that to lifting your hand 1-2 inches before attempting to strike. If you measured the force over time, with no play in the cap, the force would be proportional to pressure and a relatively smooth graph. However, with some play, you'd get a big spike, and then what looks like vibration. That would definitely weaken the threads over time (though no idea if that's 100-rounds, 1000-rounds, etc), and different rifles would wear at different rates. |
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Posted: 5/5/2021 1:55:30 AM EDT
[#48]
Another video by Backyard Ballistics (7:44)
 Serbu RN-50 Failure: A Closer Look (not endorsing or rejecting his theories, but posting for consideration) |
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Posted: 5/5/2021 2:50:06 AM EDT
[#49]
Came back looking for more info on this and am reminded why they made us take a whole engineering communications class on how to write an email and not sound like an ass.
Which I promptly ignored and sounded like an ass as a newly minted engineer until I got out to the real world and had to interact normal people. |
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Posted: 5/5/2021 2:56:32 AM EDT
[#50]
Quote HistoryQuoted: I wasn't going to comment unless someone mentioned thread tolerance. I sold my RN50 because I never could have peace of mind with it. The cap wobbled too much for me. I seriously think lug nuts may have better tolerance. Was that wobble present with a loaded round or headspace gage in the chamber? Some wobble even in a bolt action will be normal without a round in the chamber but is hidden by the fp tension. When I mean thread tolerance I mean percent thread engagement. |
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