You and I are in agreement because I'm having a hard time believing that a cartridge that operates at only about 1/3 the pressure of rifle cartridges could under any circumstances generate plasma. If it could, why wouldn't all rifle cartridges generate plasma?
is it true, or just myth?
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Well, this has indeed been a most interesting experiment, and reading all the possible reasons why the seemingly impossible happened has been just as interesting. I'll visit my son in California soon. He has some pretty high powered friends, one of whom is a doctorate in thermodynamics. Malcom works for the Lawerence Livermore National Laboratories where he helps design nuclear warheads. My son knows him because he is the father of my son's best friend. Perhaps he can help with this.
matter needs velocity to do damage (or work, like pushing a bullet down a barrel). no matter the matter (gas, liquid, or solid), no velocity means no energy or force.
i'm sure the resultant powder gases are different than normal. a gas analysis would shed some light on this.
i know from first hand experience that a light load of h110 does strange things: squib a bullet in the barrel, leave yellow powder all over the gun, hangfire, fire but at reduced velocity, etc.
smokeless powder is a big mystery. another chaotic system with too many variables.
murf
i'm sure the resultant powder gases are different than normal. a gas analysis would shed some light on this.
i know from first hand experience that a light load of h110 does strange things: squib a bullet in the barrel, leave yellow powder all over the gun, hangfire, fire but at reduced velocity, etc.
smokeless powder is a big mystery. another chaotic system with too many variables.
murf
barnbwt
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Correct me if I'm wrong, but isn't plasma exactly what the luminous fireball is? In any case, I was speaking generally, about how condensing the combustion resultants of a reaction can have an impact on the remainder's burn kinetics. As was mentioned in the Hatcher experiments, in rifles the result was excessive coking in the case, which would suggest poor combustion at what must be incredible pressures/temperatures. The clean burn exhibited in a 45acp case certainly suggests that combustion was close enough to normal to assume similar energy levels, depsite an elevated bore pressure/temperature.
I also don't think a 17WSSM with a compressed charge will result in either atomic fission or fusion, or a black hole, for that matter
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barnbwt
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H110 does not function well at low pressures; sooty black coke is the usual symptom. Different powders are optimized to burn at different temperatures, but the underlying reaction of nitrocellulose is similar (as is the energy potential stored up). Fast, high pressure powders like Tru Blue (5.7x28) are extremely clean burning, whereas moist nugget ammo composed of slower-burning nitrated political dissidents' toenails is not.
TCB
got it - the bullet doesn't move forward to obturate the barrel, so all the gases vent through the bullet/case gap (quite large as the bullet is still in the chamber throat) and down the barrel. as someone has already said, if you let the bullet move even the slightest bit, the bullet will obturate the barrel and you will get a kaboom!
murf
murf
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murf said:
That might explain why the primer pocket didn't become the vent for the powder gases as I had expected... because there was no practical way to make the chamber gas-TIGHT.
Using that model to explain what happened, even though the bullet was blocked, there there was still room for the gases from the powder-related chemistry to VENT around the bullet in the case (in the gap between the chamber and the rifling) and into the barrel. BUT even though the rod holding the bullet in place would not have filled the grooves in the barrel, threading the rod that held the bullet in place should have sealed up the end of the barrel pretty substantially...
I remain somewhat puzzled, but a bit less so than earlier.
pressure and volume are directly related. double the volume and the pressure is halved. so, the space in the barrel is probably ten times the powder space volume. in this example a 20kpsi load will reduce to 2kpsi almost instantaneously if the barrel is totally sealed. i'm sure there is a leak in there somewhere to vent the rest of the pressure. tark should be able to shed some light on this.
murf
murf
Oh my... I just read seven pages of physics because it was interesting!!!! All of it past my normal bedtime! I wish my physics teacher had told me all of this fun stuff. The only reason I stayed up late for physics before was because of the impending doom of an inevitable exam!
Someone please feed the physics junkies more often!!!!
Someone please feed the physics junkies more often!!!!
RetiredUSNChief
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I suppose the experiment could be repeated with the casing JB Welded into the chamber to see what would happen.
It would be interesting to see what would be happen if the BULLET were JB Welded in the case -- no barrel plug, just bullet stuck in the case.
barnbwt
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You can't glue a bullet in well enough to beat thousands of pounds of driving force. BTW, the 5.7x28 bullets are commonly glued into their cases, this being preferable to a crimp as a set-back preventative precisely because it does not drive pressures as high (also the 22 bullet jackets are paper thin)
TCB
TCB
Hmmm . . . you're right.
Now, as I recall, when the Army investigated the Springfield problem, one thing they found that was early ammo was tin-plated to reduce copper fouling. Over time, the bullet would cold-solder itself to the case, and that DID boost pressures.
Now, as I recall, when the Army investigated the Springfield problem, one thing they found that was early ammo was tin-plated to reduce copper fouling. Over time, the bullet would cold-solder itself to the case, and that DID boost pressures.
Hmmm . . . you're right.
Now, as I recall, when the Army investigated the Springfield problem, one thing they found that was early ammo was tin-plated to reduce copper fouling. Over time, the bullet would cold-solder itself to the case, and that DID boost pressures.
Now, as I recall, when the Army investigated the Springfield problem, one thing they found that was early ammo was tin-plated to reduce copper fouling. Over time, the bullet would cold-solder itself to the case, and that DID boost pressures.
RetiredUSNChief
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We don't need to.
The bullet would be held immobile with tark's plug. It would be sealed against gas leakage by JB Weld.
The bullet would likely deform somewhat under pressure, but it would likely remain sealed enough for this test.
I'm liking the theory of gas leakage up the rifling! With even a tight fitting rod down the bore, you've got considerable area in the throat and rifling to give the pressure somewhere to go besides backwards out of the primer. The case will expand and seal the chamber...but has an easy vent forward up into the barrel even if the threaded plug is sealed at the end. Probably even more volume (and hence lower pressure) than if the bullet moved into the barrel on a normal shot so this is a very logical explanation to what happened. Maybe.
Glue is a practical solution to the problem of keeping rounds together (as units) when being handled or used (so that there's no set back, or rounds falling apart as they are loaded or chambered).
That's different than using glue to keep the bullet from functioning as it should, when the primer is struck.
Then too, a lot of the more powerful glues are heat sensitive -- and lose their adhesive powers when things get hot.
That's different than using glue to keep the bullet from functioning as it should, when the primer is struck.
Then too, a lot of the more powerful glues are heat sensitive -- and lose their adhesive powers when things get hot.
In my earlier experiments, the plug threads brought the plug right up against the chambered round, that is, there was no middle piece; tark used the system I used in the second series with an intermediate piece because it is a bit easier to do.
"if you let the bullet move even the slightest bit, the bullet will obturate the barrel and you will get a kaboom!" As I noted, I made no special effort to seal the chamber (my goal was to keep the bullet from moving), but in some early tests the bullet did move a little resulting in a small motion of the slide. No kaboom, though, because that is not what causes a kb.
At normal small arms pressures, it is not the pressure from the burning powder that causes a kb. What causes a kb is a moving bullet with kinetic energy being stopped suddenly by an obstruction. That causes a dump of the kinetic energy in the form of heat, which softens the barrel steel so it expands like bubble gum, either bulging or (at higher pressures) bursting the barrel.
Jim
"if you let the bullet move even the slightest bit, the bullet will obturate the barrel and you will get a kaboom!" As I noted, I made no special effort to seal the chamber (my goal was to keep the bullet from moving), but in some early tests the bullet did move a little resulting in a small motion of the slide. No kaboom, though, because that is not what causes a kb.
At normal small arms pressures, it is not the pressure from the burning powder that causes a kb. What causes a kb is a moving bullet with kinetic energy being stopped suddenly by an obstruction. That causes a dump of the kinetic energy in the form of heat, which softens the barrel steel so it expands like bubble gum, either bulging or (at higher pressures) bursting the barrel.
Jim
I suspect if you repeated the experiment, with the plug only going halfway down the barrel, you'd likely bulge the barrel.
barnbwt
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Braze > Weld >> Solder >> Glue >> Bubble Gum > Spit
This could be the problem
Ah, now I understand the premise (I thought it was obstructing the bullet at the chamber using JB Weld). It would seal, but I'll bet the majority of the issue is, as mentioned, the neck of chambers generally being on the loose side for reliability. Restrain the neck from moving, and pressure will ram the rest of the case against the chamber walls. With no blow-by or bleed pressure escaping around the bullet at the neck to equalize pressure outside the case (see: HK chamber flutes) I would think it would stay pressurized far, far longer --perhaps even indefinitely at a point below the brass's/primer's yield stress.
Which raises the question; what the heck do you even do with a test-fire gun that you know has a full 30,000PSI corked up inside it (and that's after it's had a chance to cool down)? Tell the EOD team to bring something that can punch through a 1911 slide & barrel?
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