quote:

Reason this worked out the way it did is it didn't reach anywhere near 230,000 psi. When the brass case gave way at around 120,000 psi, the gas venting lowered the chamber pressure immediately, and the powder burn rate decreased dramatically.

That would be my thought but I have no actual data to support it. Only my gut feeling.

Ramrod is spot on.

Yep, exactly as I said earlier in the thread. Once the primer blows and the case head melts, the gas is released and the pressure is relieved. Gas does a lot of damage but the receiver, bolt and barrel are intact. That is how we got 120mm tank M256 tank cannon to operate at well over 100,000 Psi; primers are electric and are screwed into a steel case base, so the weak point is not the primer or brass.

I have been asked what had happened to the rest of the case.

If you look at photos 9-11, you will see it, minus the head, in the barrel.

Very unique way for vapor deposition of brass !

I learned to shoot on a Mauser 22 ,a miniature M98 .As a kid I had lots to learn about shooting . One day I fired and heard a pssst.I stopped and wondered what that noise was .The gas had come out the safety hole on the side of the receiver ! So that's what it's for , thanks Mr Mauser !

Yes. Weld muzzle closed, install strain gauge etc., stand outside, repeat procedure, you will have confirmation. Great photos, thank you.

Costly ineffficient handgrenade. Great pictures.

In order to destroy rifles a few years ago, I loaded like you did , put the barrel in the ground and used string.

I did not make pictures, it was for work and experience, not for fun.

Except that it was fun to see a Berthier 1892 being departing like a missile and staying intact.

Something that might be interesting if there ever is a next time, chronograph the shot. It would be interesting to see those numbers along with the damage.

My hats off to you Saeed. Very cool stuff.

Terry

Yes interesting thanks for the post and pictures

I have some blank powder that's a lot faster the bullseye I wonder what kind of pressures a case full of that would do.

Other than pure destruction what did you guys learn?. As to strain gauge measurement, once
the steel begins to leave the linear pressure/strain region (Hookes law) the measurement is meaningless.

quote:

Originally posted by TC1:
Something that might be interesting if there ever is a next time, chronograph the shot. It would be interesting to see those numbers along with the damage.

My hats off to you Saeed. Very cool stuff.

Terry

Also a piece of cardboard taped verticle in the wrist area of the stock would be a nice touch too. It would be interesting to see where all that powdered brass is going in relation to the shooters face.

Again, my hats off to you.

Terry

You definitely do not want to be holding it in your hands but aside from massive lacerations and burns to your hands and face, you would live.

quote:

Originally posted by ramrod340:

quote:

Reason this worked out the way it did is it didn't reach anywhere near 230,000 psi. When the brass case gave way at around 120,000 psi, the gas venting lowered the chamber pressure immediately, and the powder burn rate decreased dramatically.

That would be my thought but I have no actual data to support it. Only my gut feeling.

In spite of this, the amazing fact is that the CZ vented the gas efficiently enough that the action held together.

Normally when the case head lets go the ENTIRE FACE of the bolt takes the pressure(less what is vented away).

Just think what this means: that 60,000psi is not just pushing against the rear of the case(+- 0.130in squared), but is now pushing against the ENTIRE surface area of the bolt face(+-0.380in squared) plus the front of the lugs. This is over 4 times the pressure the action normally has to withstand.

This is why actions go when case heads blow.

Next time you try this, get a mannequin to hold it. I would like to see what damage would be done to a person.

Think about it; the actual pressure applied to the bolt is only a fraction of the actual chamber pressure (whatever it might be). On a 300 mag, the working surface for the pressure is about .197 square inches. So, assuming a chamber pressure of 100,000 PSI, the actual pressure on the bolt is 19,700 pounds, or just shy of ten tons. Any modern bolt can take ten tons of pressure. Now, high pressure gas flying everywhere is definitely not a good thing.

quote:

Originally posted by Saeed:
I have been asked what had happened to the rest of the case.

If you look at photos 9-11, you will see it, minus the head, in the barrel.

Melt" I believe the case head was crushed. With the case body locked to the chamber and the case head crush the case head separated from the case body.

F. Guffey

Saeed, Did I miss the video? Must have been quite a light show in that tunnel. CB

quote:

Originally posted by F. Guffey:

quote:

Originally posted by Saeed:
I have been asked what had happened to the rest of the case.

If you look at photos 9-11, you will see it, minus the head, in the barrel.

Melt" I believe the case head was crushed. With the case body locked to the chamber and the case head crush the case head separated from the case body.

F. Guffey

It's all semantics. In a normal case firing sequence, the powder burn is so rapid and the gases leave the barrel so quickly that the brass cannot absorb any appreciable heat energy from the burning powder gases. This has been proven time and again by plastic under bullet wads not melting when used as part of a cartridge load.

The mechanism exhibited in this case failure, in my opinion is somewhat like this: The pressure initially expands the case, sealing it to the case walls. The pressure creates a back thrust on the head of the case, which stretches the case walls immediately in front of the web, until the case contacts the bolt face. Then, the continued thrust of the case head on the bolt deforms the bolt, allowing more case stretch to occur until it exceeds the capacity of the case to stretch and the brass breaks. At this time the escaping gas has such a high velocity that the friction of the gases on the adjacent brass and steel create a plasma, a superheated gas that can vaporize adjacent steel and brass, effectively melting it. This is a local surface phenomenon, not a global heating of the brass cartridge. The vaporized metals are carried by the plasma until expansion of the high pressure gases drops the temperature below the vapor point of the metal vapor, at which time it redeposits as a thin layer on adjacent cooler surfaces.

Of course, throughout all of this, there is mechanical tearing of the brass and adjacent steel surfaces, which blows particles of metal out along with the plasma and gases.

Crushing of the case head between the high pressure gases and the bolt face is a part of the whole process, as is crushing of the case walls against the chamber. However, the brass is extremely strong in crushing, particularly in confined conditions, so the crushing is a small part of the failure, far outweighted by the the stretching, mechanical tearing, and plasma cutting parts of the failure mechanism.

dave

As I said -- awesome and terrifying to see.
Thanks for the rocket science, dave. Instructive.

quote:

Originally posted by custombolt:
Saeed, Did I miss the video? Must have been quite a light show in that tunnel. CB

I do have a video, but have been a bit busy with visitors and our CNC lathe computer has conked out.

I will process and upload the video in the next few days.

quote:

Originally posted by dpcd:
Think about it; the actual pressure applied to the bolt is only a fraction of the actual chamber pressure (whatever it might be). On a 300 mag, the working surface for the pressure is about .197 square inches. So, assuming a chamber pressure of 100,000 PSI, the actual pressure on the bolt is 19,700 pounds, or just shy of ten tons. Any modern bolt can take ten tons of pressure. Now, high pressure gas flying everywhere is definitely not a good thing.

sorry but,
I am of the understanding that pressure is equal in all directions, be it at the base of the bullet,chamber wall,
or in the direction of the bolt face.

What varies are the force/thrust figures according to the variations in specific surface areas
that are being exposed to the equalised pressure.
A larger internal case head dia. will have more bolt thrust than a smaller internal case head dia, at identical pressures.
like wise, a larger dia. base bullet will receive more thrust than a smaller dia. one, at identical pressures.

quote:

It's all semantics.

True, but time is a factor, the first failure was the firing pin spring, the ability of the spring to overcome pressure was exceeded by the pressure pushing the dent out of the primer, and then the dent in the primer went from being an inney to an outie with hot, high pressure metal cutting gas flowing back through the bolt face.

In timer that is read in milliseconds the case head was crushed, when the case head separated and no longer sealed the chamber the hot, high pressure metal cutting gas escaped through the receive.

I have tested receivers without the intent of destroying them, the receivers were sold with the understanding they could be suspect. The dent in the primer was flattened and the case heads were upset/crushed, the flash holes opened up and the primer pockets did the same. It is said normal case head expansion for factory ammo is close to .00025", my case heads expanded .025". I used R-P 30/06 cases because the case heads measured .260" from the bottom of the cup to the case head. I could have used LC almost any year but The case head thickness for the CL and military surplus case head thickness measured .200".

F. Guffey

Should be a hoot like the rest. Sure got the imagination juices flowing. Thanks.

quote:

Originally posted by Saeed:

quote:

Originally posted by custombolt:
Saeed, Did I miss the video? Must have been quite a light show in that tunnel. CB

I do have a video, but have been a bit busy with visitors and our CNC lathe computer has conked out.

I will process and upload the video in the next few days.

quote:

Originally posted by Trax:

sorry but,
I am of the understanding that pressure is equal in all directions, be it at the base of the bullet,chamber wall,
or in the direction of the bolt face.

What you have said is true up till the time the case ruptures and releases gases into the action. If the gases can't escape out fast enough to drop the pressure, the bolt face is subject to the gas pressure. The bolt face has more surface area than the interior of the case, so the pressure times the exposed surface area of the bolt is greater than that same pressure times the area of the inside of the case back. If gas release holes are present, the leaking gas may have a much lower pressure than it did inside the chamber. So, the difference in breech thrust is difficult to predict.

The separating cartridge at failure is why you use the diameter of the chamber when calculating normal breech thrust for a cartridge. The greatest breech thrust will occur at the time when the cartridge stretches and separates, so that the projected area of the cartridge that is receiving pressure is greater. Then, the bolt thrust is equal to the pressure times the area of the chamber cross section. If the cartridge doesn't separate, the breech thrust is equal to the pressure times the inside cross sectional area of the cartridge, which can be substantially lower than the ruptured cartridge.

dave

quote:

Originally posted by ssdave:
..The bolt face has more surface area than the interior of the case, so the pressure times the exposed surface area of the bolt is greater than that same pressure
times the area of the inside of the case back.

Yes of course, my previous post more or less explained the the same thing with given examples.
but pressure [not force or thrust] is still equal in all directions, which is the point I was correcting dpcd on.
There may be more or less thrust on some parts due to their different surface areas, but pressure itself still remains
equal in all directions,.... i.e.; the interior case head,case wall, boltface and base of bullet, can all have different
surface areas/thrust figures, but the pressure they are each exposed to, will be the same.

quote:

Originally posted by ssdave:
The separating cartridge at failure is why you use the diameter of the chamber when calculating normal breech thrust for a cartridge. The greatest breech thrust will occur at the time when the cartridge stretches and separates, so that the projected area of the cartridge that is receiving pressure is greater. Then, the bolt thrust is equal to the pressure times the area of the chamber cross section. If the cartridge doesn't separate, the breech thrust is equal to the pressure times the inside cross sectional area of the cartridge, which can be substantially lower than the ruptured cartridge.

Q./ in the event of a case-head separation in a severe overload situation like Saeeds test,
does gas then flow-escape around the outside of the rear section of case?

IF so, that would mean that the thrust figure [based on the chamber diameter] should be calculated using a pressure figure
that was less, than if the the case had not separated[where gases are more restricted or contained]

quote:

Originally posted by Saeed:

quote:

Originally posted by custombolt:
Saeed, Did I miss the video? Must have been quite a light show in that tunnel. CB

I do have a video, but have been a bit busy with visitors and our CNC lathe computer has conked out.

I will process and upload the video in the next few days.

Should be good video.

Has Walter been anywhere near the CNC lathe computer while you were not watching him?

Trax; no need to correct my analysis; my numbers are right. It is true that pressure acts equally in all directions; my numbers assume that. I am not sure what you are trying to correct me on. If you read my post, you will see that I said, given a hypothetical chamber pressure of 100,000 PSI, the pressure exerted on the bolt translates to 19,700 pounds. A 300 mag cartridge gives a surface area for that pressure to act on of .197 square inches. Math is math.

quote:

Originally posted by RIP:

quote:

Originally posted by Saeed:

quote:

Originally posted by custombolt:
Saeed, Did I miss the video? Must have been quite a light show in that tunnel. CB

I do have a video, but have been a bit busy with visitors and our CNC lathe computer has conked out.

I will process and upload the video in the next few days.

Should be good video.

Has Walter been anywhere near the CNC lathe computer while you were not watching him?

Funny enough, Walter had nothing to do with this.

Last year our Bridgeport milling machine packed up, and the Bridgeport agent said they can fix anything, except the computer!!

And it was the computer that had given up the ghost.

I took it apart, and went looking for something to replace it with.

We have what we call computer alley. It is a place that one can pretty much find anything concerned with computers.

One place said that motherboard and CPU are well and truly fit for a museum, as they were so old.

But, he did find one close enough, that we installed and got the machine back to work.

In fact, I made some plastic cartridge trays on it today.

The CNC lathe's replacement computer unit has not come yet.

quote:

Originally posted by dpcd:
Trax; no need to correct my analysis; my numbers are right.

The correction I made was not about your numbers on the bolt, but about your statement concerning pressure
which I distinctly highlighted earlier.....

quote:

Originally posted by dpcd:
Think about it; the actual pressure applied to the bolt is only a fraction of the actual chamber pressure (whatever it might be). On a 300 mag, the working surface for the pressure is about .197 square inches. So, assuming a chamber pressure of 100,000 PSI, the actual pressure on the bolt is 19,700 pounds , or just shy of ten tons. Any modern bolt can take ten tons of pressure . Now, high pressure gas flying everywhere is definitely not a good thing.

There is no fraction of pressure, since the actual pressure applied in the direction of the bolt is exactly the same amount of pressure thats is applied
to the case wall,internal case head,or projectile...all of those surfaces would be equally subject to 100kpsi.

What varies are the amounts of Force/thrust created according to those individual variations in surface area that are all being exposed to an identical amount of pressure.
Which is what your math shows concerning the bolt.

Hence, the more appropriate statements would have been:

- "the actual pressure applied to the bolt is only a fraction of the actual chamber pressure"
- "the actual force applied to the bolt is only a fraction of the force applied to the chamber."

- "the actual pressure on the bolt is 19,700 pounds"
- "the actual force on the bolt is 19,700 pounds"


- "Any modern bolt can take ten tons of pressure"
- "Any modern bolt can take ten tons of force"


ITs important to remain aware of the difference between pressure and force.

The difference between chamber pressure and linear force exerted onto the bolt is what I was explaining; sorry I used the wrong word. I am well aware of the difference.

An amazing testimony to modern metallurgy, but not to say that our early 1900s 98s or even older commercial guns would fare as well.

I have only participated in one incident of firearm destruction and I di not note much difference in the shot until I wen to acquire the rear sight for the next shot and hat thought that blade had come out.

Not until I tipped it up did I note that not only was the blade not there the top strap of that Ruger Super Blackhawk was missing also.

DANG, and that was a really . . . REALLY great shooting gun too.

Upon reflection I know exactly what happened and it was 100% my fault!

A fellow shooter gave me the top strap about a year later after he found it lying in the grass down range.

Sits on my loading bench as a reminder.

Pending Saeed's posting of the video kaboom,
I reckon a CZ 550 Magnum might be OK to build a .408 Chey-Tac on ...
but keep the pressures down to one-quarter of Saeed's kaboom load.
Should be OK with that bolt thrust,
as CZ roll-stamps the action on their .505 Gibbs to indicate 3800 bar or 55,100 psi maximum working pressure.
Saeed tried to do over 4 times that on a smaller casehead.
If he had tried 232,000 psi in a .505 Gibbs ... more spectacular KABOOM?
The skeletonized bolt face would not be a strengthening feature.

A reinforcing bolt in the stock grip would not have helped much here:

Of course the gun didn't "Blow UP". THe breech
and barrel held. The case head failed and the
gas in the magazine well blew the stock.
Once more; What have you learned ?.

Interesting experiment, thanks for sharing! Did you happen to catch a muzzle velocity?