The M18 accident; what might have happened and how it could be prevented

[Bronezhilet]

First off, notice the "might" in the title. It is not yet known what exactly happened. What I'll be talking about is something I heard from someone close to the people involved. It might turn out to be not true, or it might be true. To be sure we have to wait for the official report of the investigation.

 

Second, it might seem I am attacking the victims of the accident, this is not the case. But if they made mistakes, I will point them out.

 

 

So most of you have probably already heard of the accident with the M18 Hellcat. What I have heard from people close, is that the round went off when they opened the breech after a misfire, or slightly after they opened the breech. So, a misfire huh. Nasty stuff when it involves explosives.

 

So, what happened?

 

Well, misfires happen. There's nothing strange about that. I assume a lot of you have experienced misfires with small arms, and you know the procedure of dealing with them. But with misfires like these are handled (completely) differently. I asked around a bit, and apparently the gunner waited a few minutes after the misfire before he opened the breech. This is good, but not good enough. Not by a long shot. If I remember correctly, when your small arms firearm misfires you keep the barrel pointing down range for at least 30 seconds. After 30 seconds you can safely assume the round will not go off by itself. It's different when a proper amount of explosives is involved. You do not wait 30 seconds.

 

You wait at least 30 minutes. But between a misfire and waiting is another step. But I don't know if that step is possible on a Hellcat. More modern tank guns have two firing systems. The normal one, and an emergency one. If there was a misfire you were supposed to try the emergency firing system next, and if that didn't work: Time to wait.

 

After waiting 30 minutes there are two things you can do. The first is to open the breech and check everything. Carry the round to a safe place, and blow it up. This is usually what you can do with normal, proper rounds. But in this case, with more shady ammunition I would go for option two: Call Ordnance. There are multiple things that could be wrong with the round, and I'm go out on a limb here and claim that the gunner did not have Ordnance training. In the military, if something goes wrong, Ordnance immediately becomes the supervisor of everything that happens. There might be Generals running around, but that mere Sarge (or whatever rank they have in the US) is in charge.

This is what Ordnance would most likely do:

- Establish what round is actually in the gun. Is it an original WW2 round, or is it aftermarket? What primer did they use? What powder? Is it an AP shell, or HE? Does the shell have a fuse? If yes, what type of fuse?

- Try to establish what happened with the round before it went into the gun. How was it stored? Did you put it in your shed, or in a bunker with AC?

This is all to determine one thing: Is the round stable? In other words: Can I move the round?

 

If the round is determined to be stable, Ordnance can do two things.

1. Open the breech from a safe distance, and making sure the round will be caught before it hits something. Considering an historic piece of equipment is involved, this can result in the best possible ending. Which is a round being ejected without problems. But it is possible that the round will detonate inside the vehicle, destroying the tank and sending shrapnel all over the place. For Ordnance, the problem isn't the tank being nuked, it's the shrapnel.

 

2. Remove the gun from the turret and move it to a safe place. Ordnance will put at least three shaped charges on the outside of the chamber. One aimed at the primer, one aimed at the propellant and the last one aimed at the shell itself. The whole barrel will then be covered with several tons of dirt and the charges detonated. Voila, another safe ending to a dangerous situation. The gun is properly ruined, but nobody is hurt (except maybe some feelings).

 

I'm assuming that the gunner knew how to handle firearms and various weapons. He had fired the gun before, he knows how it works. He might not have much experience with misfires, but he does know that he should wait a bit before opening the breech. But at this point, it's not a round you have in the gun. It's not a misfired round. It's not a nuisance. It's a faulty round.

It's an explosive. It intends to kill. And it intends to kill you. And it intends to kill you immediately.

 

Treat it as such. Don't touch anything. Sod off to a safe place. Call Ordnance.

[Meplat]

Only one "system" with two methods of actuation on the Kitty. The electrical firing is just a solenoid that trips the mechanical release.

 

The vast majority of civvy arty loads are homerolled. If you're lucky you have some original cases, some projos that are sound, and from there it's "Figure it out".

In the case of the 76, most are taking the far more common 3" naval projos and turning down the obturator rings (The 3" runs at a higher pressure than the '76, even though the nominal shot size is the same.).

 

The projos are usually "set" in the case (You'll see masking tape used sometimes) and not solidly crimped (improves case life) which can cause a mess when dealing with a misfire or fouling . Seen more than a few times where the projo pulls out and you're left with a spill of propellant as the case is drawn out.  Then the cleaning rods come out and the projo is persuaded to back out the tube.

 

Priming can vary. A lot. Considering the number of misfires I've seen with original, supposedly "sound" arty primers, versus often homerolled primers I'm not going to guess as to what was used.

 

Propellant can be variable, and here is where I think there was an issue.  The stuff can absorb moisture which will change it's behavior to an extent. How it's stored will also cause issues. Too much heat will "cook" the volatiles from it (when you open a can of surplus ammo and get that sweet-ish nitro smell for example) and change it's burn rate and sensitivity.  So a weak primer plus a load of surplus propellant that was not well stored at some time in it's life, and you have potential problems.

 

Lastly is an issue with surplus armor in general, and that is most of it is old, and parts, especially for the noisy bits are incredibly scarce (By design).  We have no idea what state the lockwork was in and how sound or unsound it may have been.   We also do not know how well treated or mistreated they were in previous use, and these things saw LOADS of previous use (or abuse) . 

Unless you're very very wealthy and have scads of free time, you're having to rediscover everything about your chosen piece from scratch, as there is shockingly little hard info out there about them ( Also "By design"), and you're having to do this when you can, as you can.

 

All of which leads to the potential for accidents like we had recently. Any one of a number of potential things could have caused it, and eventually you can get so wrapped up in the safety that you're afraid to shoot the silly thing.  (kind of defeating the purpose of owing a live eargesplittenloudenboomer.)

 

It's definitely a hobby that has the potential to get messy. 

I'm just hoping some shitbird bureaucrat does not use this as an excuse to close the registry on DD's, because compared to some hobbies, it has a fantastic safety record considering the energies and potential for "oh shits" you're dealing with.

[Toxn]

Nah, they'll just wait until some idiot makes a IRA-style mortar and tries to use it to blow up his school. Which, given the dearth of imagination shown by your average wanna-be school blower-upper, might take a while to happen.

[Bronezhilet]

Only one "system" with two methods of actuation on the Kitty. The electrical firing is just a solenoid that trips the mechanical release.

 

The vast majority of civvy arty loads are homerolled. If you're lucky you have some original cases, some projos that are sound, and from there it's "Figure it out".

In the case of the 76, most are taking the far more common 3" naval projos and turning down the obturator rings (The 3" runs at a higher pressure than the '76, even though the nominal shot size is the same.).

 

The projos are usually "set" in the case (You'll see masking tape used sometimes) and not solidly crimped (improves case life) which can cause a mess when dealing with a misfire or fouling . Seen more than a few times where the projo pulls out and you're left with a spill of propellant as the case is drawn out.  Then the cleaning rods come out and the projo is persuaded to back out the tube.

 

Priming can vary. A lot. Considering the number of misfires I've seen with original, supposedly "sound" arty primers, versus often homerolled primers I'm not going to guess as to what was used.

 

Propellant can be variable, and here is where I think there was an issue.  The stuff can absorb moisture which will change it's behavior to an extent. How it's stored will also cause issues. Too much heat will "cook" the volatiles from it (when you open a can of surplus ammo and get that sweet-ish nitro smell for example) and change it's burn rate and sensitivity.  So a weak primer plus a load of surplus propellant that was not well stored at some time in it's life, and you have potential problems.

 

Lastly is an issue with surplus armor in general, and that is most of it is old, and parts, especially for the noisy bits are incredibly scarce (By design).  We have no idea what state the lockwork was in and how sound or unsound it may have been.   We also do not know how well treated or mistreated they were in previous use, and these things saw LOADS of previous use (or abuse) . 

Unless you're very very wealthy and have scads of free time, you're having to rediscover everything about your chosen piece from scratch, as there is shockingly little hard info out there about them ( Also "By design"), and you're having to do this when you can, as you can.

 

All of which leads to the potential for accidents like we had recently. Any one of a number of potential things could have caused it, and eventually you can get so wrapped up in the safety that you're afraid to shoot the silly thing.  (kind of defeating the purpose of owing a live eargesplittenloudenboomer.)

 

It's definitely a hobby that has the potential to get messy. 

I'm just hoping some shitbird bureaucrat does not use this as an excuse to close the registry on DD's, because compared to some hobbies, it has a fantastic safety record considering the energies and potential for "oh shits" you're dealing with.

So tl;dr: An Ordnance dude wouldn't even dare to think of moving it. At least not before it sat for, I dunno, a few hours?

 

My guess is that either primer or propellant was slow burning, the shock of ejection ignited properly working primer/propellant, setting off the rest of the propellant

 

I'm not saying everybody should stop shooting cannons, far from that. I really like working, historic guns. But in my opinion this was absolutely preventable. Yes, misfires happen, but the 30 minute rule is present in every single manual of things containing explosives. Even a 'mere' Centurion gunner could tell me about the 30 minute rule. It's not rocket science. I can't stress it enough, it's out there to kill you, treat it as such.

[Meplat]

So tl;dr: An Ordnance dude wouldn't even dare to think of moving it. At least not before it sat for, I dunno, a few hours?

 

My guess is that either primer or propellant was slow burning, the shock of ejection ignited properly working primer/propellant, setting off the rest of the propellant

 

I'm not saying everybody should stop shooting cannons, far from that. I really like working, historic guns. But in my opinion this was absolutely preventable. Yes, misfires happen, but the 30 minute rule is present in every single manual of things containing explosives. Even a 'mere' Centurion gunner could tell me about the 30 minute rule. It's not rocket science. I can't stress it enough, it's out there to kill you, treat it as such.

Kind of.  I'm guessing the propellant was damaged/damp, and there was an issue with whatever wadding causing it to shift forward when loaded. When it hung and someone hit the GTFO lever, the propellant that was good setback into the stuff that was smouldering, and Newton's laws took over from there.

 

Anyhow, you'd have to be at a shoot to see why the 30 minute idea just would not work.

[ZloyKrolik]

Considering that a video crew was there filming the shoot, and one of the crew survived until the 1st responders  got there and spoke to him, it is a good chance that the cause of the accident will be verified.

[Cannonmn]

I've been in touch with fellow Cannon shooters who have what I believe to be accurate info about the tragic accident. I've been posting the latest reports and my interpretation on the Graybeard Blackpowder cannons and mortars forum, and I'd link to there but I'm not sure that's allowed here. Thread is "Cannon accident." I also thought it had something to do with a misfire, a week or so ago, then got better info. What I am sure of now is that the crew of the M18 in Bend were of course hand loading their ammo, but they took many shortcuts which made their ammo very dangerous and created much higher chamber pressures than the gun could withstand, thus on what we think was the third round fired that day, the gun's breechblock was shattered and the breech ring cracked at the instant of firing. The fragments and hot gas released into the occupied turret caused the fatal injuries.

[Khand-e]

You're allowed to link to them.

[Cannonmn]

Link to more details-page 2 has the later info, reply 43 is latest. Next two I think confuse things.

http://www.go2gbo.com/forums/blackpowder-mortar-and-cannon-sponsored-by-seacoast-artillery/cannon-accident-310747/30/

[LostCosmonaut]

Welcome to SH.

[CrashbotUS]

If you want some serious pucker material, go down on a gun line when one of them has a hung round or misfire. Even with all the modern equipment and proper ammunition it is pretty scary, I can't imagine doing it with home rolled

munitions. 

Watching some poor mortarman catch a mortar round as they slide it out of the tube or seeing a howitzer crewman ram a 155mm shell back down the cannon tube while someone else removes it from the breach and carries them over to the "dud pit" will make you happy you picked a different job. 

[Khand-e]

or seeing a howitzer crewman ram a 155mm shell back down the cannon tube while someone else removes it from the breach and carries them over to the "dud pit" will make you happy you picked a different job. 

 

Erm, how long did you do this exactly? I'd simply be surprised if I finished that job without seeing a "dud carrier" get pink misted at some point.

[Bronezhilet]

Watching some poor mortarman catch a mortar round as they slide it out of the tube or seeing a howitzer crewman ram a 155mm shell back down the cannon tube while someone else removes it from the breach and carries them over to the "dud pit" will make you happy you picked a different job. 

Don't tell this to Dutch EOD guys. The whole EOD would collectively flip their shit.

[CrashbotUS]

Erm, how long did you do this exactly? I'd simply be surprised if I finished that job without seeing a "dud carrier" get pink misted at some point.

 

I was an artillery observer for over 15 years and never witnessed anyone being injured or killed while clearing a gun tube.  Attending fire support mission briefings on the gun lines, I've seen many misfire clearing procedures take place. It's taken very seriously, check fire is called and everything comes to a halt until the rounds are cleared or the gun is otherwise made safe. 

FM 3-22.90 covers clearing procedures for 60mm to 120mm mortars, check it out if you like. TM-9-2350-311-10 covers unloading and misfire procedures for howitzers.  

 

For howitzer misfires there are certain things the crews can do to remove the primer, powder, and unload the round after the "safe period"  but before needing to involve EOD (hang fires are always turned over to EOD) . Mortar rounds are made safe by the crew and stowed  someplace at least 100 meters away until they can be disposed of. 

[ZloyKrolik]

I just saw a preview of the WoT December 2015 commercial, and it had the M18 "Rachel" in it.

[Walter_Sobchak]

I just saw a preview of the WoT December 2015 commercial, and it had the M18 "Rachel" in it.

Yes, The Chieftain was there shooting a video about a week before the accident.  He made a statement about it over in the Chieftain's Hatch section of the WoT forum.  I'd link to it, but I'm too lazy to find it right now. 

[Belesarius]

I've been in touch with fellow Cannon shooters who have what I believe to be accurate info about the tragic accident. I've been posting the latest reports and my interpretation on the Graybeard Blackpowder cannons and mortars forum, and I'd link to there but I'm not sure that's allowed here. Thread is "Cannon accident." I also thought it had something to do with a misfire, a week or so ago, then got better info. What I am sure of now is that the crew of the M18 in Bend were of course hand loading their ammo, but they took many shortcuts which made their ammo very dangerous and created much higher chamber pressures than the gun could withstand, thus on what we think was the third round fired that day, the gun's breechblock was shattered and the breech ring cracked at the instant of firing. The fragments and hot gas released into the occupied turret caused the fatal injuries.

Welcome to SH. Thanks for the info.

[Walter_Sobchak]

more on the ammo from the accident.  http://weaponsman.com/?p=27364  Scroll down a bit to this comment:

 

One thought on “Tank Destroyer Fatalities — Caused by Bad Reloads?”

1. Ordhistorian November 27, 2015 at 11:55

   Yes indeed, they were using military primers designed for 40mm Bofors cases. They did not use the 19 inch long igniter tube on the top of the primer, that would be filled with black powder to ignite the propellant. They fired 2 or 3 rounds before the gun blew up, and the first couple of rounds were hang-fires. That is when they started putting a black powder igniter charge in the bottom of the case. All of their rounds were short, so instead of raising the barrel, Steve said “I guess we need to add more powder”, upon which Chuck (the supposed explosive expert that was being paid $1500 a day to be there) said “Say no more”. He then increased the powder charge from 3 Lb. to 3-1/2 Lb. and threw a handful of black powder in to mix with the increased propellant charge, intermixing it with the M30 cannon propellant.

   I don’t know if they were using a cardboard “distance piece” to hold the powder in place at the bottom of the case. If a distance piece was not used, the powder would lay on its side, allowing the ignition to flash over the top of the charge and possibly detonate it instead igniting it to burn.

   The M30 propellant they were using is designed to be used in 155mm Howitzer propelling charges. The grains are much larger (0.46 inches X 0.935 inches) than the M6 propellant (0.3 inches X 0.7 inches) which was designed in the 50’s to be used in the 76mm gun. It is no wonder they were having hang-fires, because the powder grains were too big and slower burning. Intermixing the black powder with the propellant was insane! Anyone that has ever read a reloading manual knows that you never mix powders in the same charge. Adding powder instead of raising the muzzle is the stupidest thing in the world for any shooter to do.

   Lastly, as an added note, Chuck Hegele, the supposed “Explosives Expert” has now been involved in blowing up 3 pieces of artillery, the Hellcat twice, once in the summer of 2013, and most recently this particular incident. In the Summer of 2014 he blew up his own 8 inch Howitzer, and the video of that is on YouTube. The first incident with the Hellcat in 2013 occurred because they were using 50 BMG primers, instead of military artillery primers that have an isolated floating firing pin that seals off any gas from the primer. They had a pierced primer in the 2013 incident, and gas blew back through the firing mechanism, destroying it. Luckily no one was hurt at that time.

[Belesarius]

I don't know a ton about explosives, but mixing propellant type sounds like a freaking BAD IDEA to me. The fact that a 'professional' went along with it is more than a little disturbing.

 

It sounds like it was a miracle these guys didn't kill someone before this incident.

[Walter_Sobchak]

Here is the video of the 8 inch gun that "Ordhistorian" references.  

 

https://www.youtube.com/watch?v=IzdQq1YwE0A