Firearms industry standard engineering safety factor: Youtuber almost dies from exploding gun

[moonbogg]

What is it? 2:1? 3:1? A youtuber named Kentuckyballistics had a .50cal rifle blow up in his face due to a "hot load" in a round. He said the rifle was designed for 55kpsi pressure, yet the manufacturer said the pressure required to cause the gun to blow up would be 85kpsi. He seemed to think that was a lot, but that's only a safety factor of just over 1.5. It seems low to me. Is that normal for a firearm to have such a low factor of safety? 55,000psi is fine but 85,000psi and you're dead? I wouldn't trust a lawn chair with a safety factor of 1.5 let alone a .50cal rifle.

 

[[DHT]Osiris]

What is it? 2:1? 3:1? A youtuber named Kentuckyballistics had a .50cal rifle blow up in his face due to a "hot load" in a round. He said the rifle was designed for 55kpsi pressure, yet the manufacturer said the pressure required to cause the gun to blow up would be 85kpsi. He seemed to think that was a lot, but that's only a safety factor of just over 1.5. It seems low to me. Is that normal for a firearm to have such a low factor of safety? 55,000psi is fine but 85,000psi and you're dead? I wouldn't trust a lawn chair with a safety factor of 1.5 let alone a .50cal rifle.

A 50% increase in a thing is probably well outside operating ranges for most things that have a recommended/required rating. How about a lawnmower? Vague googling says walk behind/riding mowers sit at around 3k RPM. There's zero chance in hell I'd walk behind one that was altered to run at 4500, as I wouldn't trust the mechanicals keeping it together to not fly apart and slice my feet off (or end up in my head, bonus points for the reference!).

Consider the vehicle comparison: If you've got a set of P Zero tires, newest ones apparently rated for 230MPH, are you really going to be surprised if they blow apart at 350MPH?

 

[highland145]

So did he load it hot and, if so, how hot?

 

[highland145]

Hot load.

GRAPHIC: Georgia man loses leg after lawnmower shooting stunt goes wrong

A Georgia man has lost his leg after shooting a lawn mower packed with an explosive known as Tannerite.We get a lot of calls about Tannerite. It can be extremely dangerous if it is not used correctly, says Walton County Sheriff Joe Chapman.Chapman released

news3lv.com

 

[Torn Mind]

Knowing my from Redfin viewing of Kentucky.....he was likely pretty far from civilization and major hospitals.

Clarksville TN to Nashville TN is about 50 miles. Fort Campbell KY to Nashville is about 60 miles.

KentuckyBallistics is in Murray Kentucky and about 120 miles from Nashville drive-wise. He's in the southwestern part of that state.

Richard Zednik had a sliced jugular vein by a skate and was saved by "stopping the bleeding."

Also, I was just going to listen to a few minutes but wound up watching nearly all of it. That's talent

 

[KB]

That's a >50% increase. Would you expect a kayak that rated for 250 pounds to handle 375lbs? nope

This guy is the reason why coffee cups say "CAUTION: HOT"

 

[sdifox]

The 50mm should had beem built as tough as the 16" gun on the IOWA class battleships

 

[right_to_know]

Posters are comparing apples to oranges.

You're not going to accidentally go 100mph more on car wheels rated for 200mph but there are plenty of faults that can push gun pressures up and those are often catastrophic in the event of a squib load or partial barrel obstruction.
Overloading a kayak lets the user see it slowly sink as they put more weight on it.

 

[[DHT]Osiris]

Posters are comparing apples to oranges.

You're not going to accidentally go 100mph more on car wheels rated for 200mph but there are plenty of faults that can push gun pressures up and those are often catastrophic in the event of a squib load or partial barrel obstruction.
Overloading a kayak lets the user see it slowly sink as they put more weight on it.

Yeah, and I wouldn't expect a firearm mfg to mfg a firearm to withstand double the intended load, that's just silly. A .50cal would probably be double the cost, and double the weight to withstand double the rated load.

What firearm survives a partial barrel obstruction with a rated load? A .22?

 

[herm0016]

Yeah, and I wouldn't expect a firearm mfg to mfg a firearm to withstand double the intended load, that's just silly. A .50cal would probably be double the cost, and double the weight to withstand double the rated load.

What firearm survives a partial barrel obstruction with a rated load? A .22?

Maybe a pellet gun...maybe.

 

[brianmanahan]

this reminded me of the 49ers fan here who lost his thumb from a big pistol

pretty gross pics

 

[Scarpozzi]

.50 Cal Blows Up in Shooter's Face | Military.com

www.military.com

Is this the video?

Yeah....be weary of buying cheap ammo from Russia and places too. A lot of manufacturers won't warranty guns if you shoot that stuff.

 

[moonbogg]

Posters are comparing apples to oranges.

You're not going to accidentally go 100mph more on car wheels rated for 200mph but there are plenty of faults that can push gun pressures up and those are often catastrophic in the event of a squib load or partial barrel obstruction.
Overloading a kayak lets the user see it slowly sink as they put more weight on it.

Indeed they are. I'm not sure that increasing the RPM of a blade to 150% of max rated increases the tensile stresses by 150% on the blade or other components. I don't know if those forces scale linearly like that. I suspect certainly not. For instance, one analysis I read for a marine propeller compared stress values at 4000rpm and 6000rpm, a 50% increase, the same as we're talking about here. The stress at 4000 rpm was 285 Mpa while at 6000 rpm was 739 Mpa, an increase of nearly 160%, NOT 50%. Safety factors could be based on material stress headroom, and that headroom may then be translated into a rating value based on usage terms the consumer can understand, such as an RPM rating for a lawn mower or a speed rating for a tire. The percentage of allowable increase in usage is not the same percentage of headroom in the strength of the materials.
With pressure, the increase in force is a direct product of pressure and surface area. Shock loads and other factors might reduce the safety factor further in a nonlinear way, similar to the propeller.
In the video, we can see that the barrel and chamber of the gun appear to be intact, yet the threads on the end cap failed. That was the weakest link in the design and happened to also be the most critical area of the gun as it related to the safety of the user. That end cap is right in front of your face. It makes we wonder if the failure mode of the gun was adequately considered and tested. But, I'm not familiar with firearm design, so that's why I'm asking questions about it. I get the feeling a lot of people will be asking questions about it as well after what happened.

 

[[DHT]Osiris]

Indeed they are. I'm not sure that increasing the RPM of a blade to 150% of max rated increases the tensile stresses by 150% on the blade or other components. I don't know if those forces scale linearly like that. I suspect certainly not. For instance, one analysis I read for a marine propeller compared stress values at 4000rpm and 6000rpm, a 50% increase, the same as we're talking about here. The stress at 4000 rpm was 285 Mpa while at 6000 rpm was 739 Mpa, an increase of nearly 160%, NOT 50%. Safety factors could be based on material stress headroom, and that headroom may then be translated into a rating value based on usage terms the consumer can understand, such as an RPM rating for a lawn mower or a speed rating for a tire. The percentage of allowable increase in usage is not the same percentage of headroom in the strength of the materials.
With pressure, the increase in force is a direct product of pressure and surface area. Shock loads and other factors might reduce the safety factor further in a nonlinear way, similar to the propeller.
In the video, we can see that the barrel and chamber of the gun appear to be intact, yet the threads on the end cap failed. That was the weakest link in the design and happened to also be the most critical area of the gun as it related to the safety of the user. That end cap is right in front of your face. It makes we wonder if the failure mode of the gun was adequately considered and tested. But, I'm not familiar with firearm design, so that's why I'm asking questions about it. I get the feeling a lot of people will be asking questions about it as well after what happened.

Yes, I'm aware that it was apples and oranges, my point though was that engineering is apples and apples. 150% tolerance increases is not normal for commercially manufactured goods, because there's costs involved that could be shaved off by reducing that to more like 120%.

So, regarding firearm loads specifically, here's a nice breakdown of loads and effects:

Primal Rights

Primal Rights

www.primalrights.com

41g was default load, catastrophic failure at 48g, or 117% increase. May not have specifically caused damage to the firearm in this example (they didn't say) but given the tight tolerances there, I would never want to be near a firearm that had a 125% load in it, much less a 150%. In retrospect the above .50cal might actually be overengineered already if it's able to withstand a 150% load. Makes sense for a $10k firearm.

EDIT: an exception to the above would be for any firearm specifically designed for overpressured ammunition, which I'm sure a .50BMG isn't given that there's like, one ammunition for it.

Overpressure ammunition - Wikipedia

en.wikipedia.org

 

[moonbogg]

The accepted standard for safety factor in product and component (including machine) design is 2:1 as a general baseline. If human safety is at risk, such as in the paintball industry, the industry standard factor of safety (minimum) is 3:1 for pressurized vessels and air guns. Those things hold 3000psi in normal use, and they don't explode until they see at least 9000psi. These things I am already aware of, and that's why I was curious about firearms safety factor because the safety margin seems close compared to other industries.
Regarding the gun that failed, it was not a $10,000 gun. It was $875 on release and just over $1000 now. It was designed specifically to be the cheapest, simplest .50 BMG possible. I have the benefit of hindsight of course, but I'm wondering if they did failure testing and if they got to see that end cap blow off straight back like that.

I'm starting to think that when it comes to firearms like a .50BMG, they are basically pushing material science to the limit already, so it simply might not be practical to have a huge safety margin. For instance, the yield of regular steel is around 30kspi. That means if you simply expose a flat section of a flat plate of steel to .50BMG pressure, it will start to deform and smash that steel plate without any stress risers or moments. It's like smashing a piece of cheese between your fingers, all you need is pressure. A typical firearm material is 4140 heat treated alloy with a yield of around 130kpsi, so even at best case using this steel, safety factor is already around 2.6 in perfect conditions. I still think the barrel should split open before an end cap comes flying off in your face.

 

[gorobei]

gun jesus did a special on gun failure (in/out of battery). he covers some of the op vid incident.

50 cal is on the extreme end of the cartridge spectrum, i would be overly cautious when it comes to firing factory spec much less overpressure loadings.

he goes over gun maker failsafing measures on some other guns.

 

[gill77]

gun jesus did a special on gun failure (in/out of battery). he covers some of the op vid incident.

50 cal is on the extreme end of the cartridge spectrum, i would be overly cautious when it comes to firing factory spec much less overpressure loadings.

he goes over gun maker failsafing measures on some other guns.

I really like Ian's videos. Knowledgeable guy.

Glad he mentioned squib loads. Not super common, but they do happen.

 

[Red Squirrel]

Holy crap that's crazy stuff. He got lucky as hell that he survived that, but also lucky he did not lose his eye. That was dangerously close.

 

[moonbogg]

Video response from the gun designer. He said the gun design is safe under any normal conditions, and I believe him. He's going to make an analysis video where he might try to replicate the failure and explain the analysis to help people understand what took place. I'm looking forward to this hugely. I want to understand.

Here is a great video talking about the event and explaining the importance of taking failure mode into account and offering some suggestions to make the failure mode more favorable for the safety of the shooter. He suggests that perhaps ventilation holes in the end cap could make the design more safe should it explode from a ridiculous load or barrel obstruction. In fact, the ventilation holes might prevent an explosion in such instances, which I think was his point.

 

[Kaido]

GRAPHIC: Georgia man loses leg after lawnmower shooting stunt goes wrong

A Georgia man has lost his leg after shooting a lawn mower packed with an explosive known as Tannerite.We get a lot of calls about Tannerite. It can be extremely dangerous if it is not used correctly, says Walton County Sheriff Joe Chapman.Chapman released

news3lv.com

 

[K1052]

Yeah....be weary of buying cheap ammo from Russia and places too. A lot of manufacturers won't warranty guns if you shoot that stuff.

I've shot a ton of Wolf and TulaAmmo over the years. While dirty crap it always goes bang and not KABOOM in my face as the gun explodes from way out of spec pressure.

 

[[DHT]Osiris]

Also always this classic:

 

[Scarpozzi]

I've shot a ton of Wolf and TulaAmmo over the years. While dirty crap it always goes bang and not KABOOM in my face as the gun explodes from way out of spec pressure.

I know....but my point is that I've purchased a few AR-15 uppers from a small company that specifically have tags saying it will void your warranty. I assume they're not the only company to have those restrictions and there's likely some questions either surrounding the manufacturing of the ammo. I suppose it could be they don't want you shooting OLD ammo that's been sitting in warehouses for years either.

I remember seeing Wolf all over the place. I'd trust them pretty well for being cheap/dirty ammo....but there were a few gun shops that had Russian and Czech rounds that were basically unlabeled for dirt cheap. They were just in brown boxes and ammo cans in bulk. (was around 2007/2008 that I saw them) I remember seeing places selling tracer rounds too....always wanted to buy those. =P

 

[Baked]

When I saw that video, all I can think about was, yup, saw this coming a mile away. He's so damn lucky to be alive and not blind from that shit exploding in his face. You play with fire, you're bound to get burned.

 

[Red Squirrel]

What exactly did he do wrong? Never really got much context. Is it because the gun was too hot when he placed another round in it?