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Detonation ?
torizus
Member Posts: 120 ✭✭
What is the general consensus among experienced loaders when it comes to "light loads" and so called detonation ? Does light powder volume versus remaining case volume increase the chances of a round detonating in such a manner as to spike pressure to the point of destroying a handgun?
One example I was given is when a minimum powder load is shifted in a case such as when the barrel is pointed down and then the gun is fired, the position or lay of the powder can have several flash points thereby increasing pressure. Is this common ?
One example I was given is when a minimum powder load is shifted in a case such as when the barrel is pointed down and then the gun is fired, the position or lay of the powder can have several flash points thereby increasing pressure. Is this common ?
Comments
I have seen chronograph results change in relation to powder position in rifle cases with lead bullets. I have not seen a velocity spike that indicated abnormal pressure.
Recently the 125 grain bullet in a 357 mag and all 41 mag loads using Blue Dot were pulled from the books. I wonder if a inconsistent pressure spike was seen, causing the recall.
I tend to use Unique for reduced loads in large pistol cases, I have never heard of that powder causing issues, real or imagined. My go-to powder for rifle cases and lead bullets is 2400 although 5744 might be better in some.......
I spoke to Alliant's head ballistician about the Blue Dot issue, and all he was willing to tell me was that they saw "abnormal results" in the pressure curves in those two cartridges. He would not specify what that meant - clearly out of legal caution, for which I do not blame them.
Powder position in the case can and does cause velocity variation, but I personally believe that you have to deliberately position the powder to create it. Normal handling and cycling of the gun between shots will evenly distribute the powder in the case -- unless you are in the habit of shooting at your toes. (If you are, the velocity won't matter at that range, LOL!)
I'll sleep better knowing this phenomenon is a possibility but not probable. Although it is something to put in my FYI and best practices box.
I went head first into this hobby and bought just about any dang thing someone makes for reloading not to mention all the guns, the inspiration to try reloading came from this forum but the interesing and fun part that sustains it is knowing I have access to the pros knowledge when I need it...thanks again.
explain this one, and the load data given is "as best remembered"
There were 9 empty cases on the table, and 9 holes in the target when the 10th round was fired. Shooter (my gunsmith) lost parts of several fingers.
He feels that this one may have been due to metal fatigue, but also holds that a "dual ignition" can also occur. IE the bullet starts to move under pressure, the increased volume causes the pressure to drop allowing the bullet to stop, and than when the pressure builds again it's dealing with a "obstructed barrel" situation (pressure exceeds metal strength before the bullet starts moving again).
A few years back there was some imported (Chilean?) 50BMG ammo that blew up several M-2's. He witnessed one "misfire" where the operator was fast enough on the charging handle that when the gun didn't fire, he ejected the case at which time the powder flamed off (bullet was still in the throat). Not exactly the same as a "light load" but a similar/related cause.
BTW the "proper name" is S.E.E. "Secondary Explosive Effect" (note EFFECT, IE like an explosion, not a actual explosion)
IIRC, SEE HAS been duplicated in lab testing, and it's a somewhat random thing IE: something like 1 in 1000 tries
RR and bp
explain this one, and the load data given is "as best remembered"
There were 9 empty cases on the table, and 9 holes in the target when the 10th round was fired. Shooter (my gunsmith) lost parts of several fingers.
He feels that this one may have been due to metal fatigue, but also holds that a "dual ignition" can also occur. IE the bullet starts to move under pressure, the increased volume causes the pressure to drop allowing the bullet to stop, and than when the pressure builds again it's dealing with a "obstructed barrel" situation (pressure exceeds metal strength before the bullet starts moving again).
A few years back there was some imported (Chilean?) 50BMG ammo that blew up several M-2's. He witnessed one "misfire" where the operator was fast enough on the charging handle that when the gun didn't fire, he ejected the case at which time the powder flamed off (bullet was still in the throat). Not exactly the same as a "light load" but a similar/related cause.
BTW the "proper name" is S.E.E. "Secondary Explosive Effect" (note EFFECT, IE like an explosion, not a actual explosion)
IIRC, SEE HAS been duplicated in lab testing, and it's a somewhat random thing IE: something like 1 in 1000 tries
Wow, If I had to hazard a guess it would be a failure of the receiver at the thin spot where the feed tube passes under the barrel, it is a known weakness on lever guns. Many have failed at that spot with similar results. It may have been cracked for years without being visible, the cracks are hard to detect unless the feed tube is removed and the metal is fluxed in that area. He just happened to pull the rigger when the crack decided to let go, destroying the gun, and unfortunately injuring your friend.
Here's a lab test of a multiple charge of Bullseye being fired.
In a cartridge that has an excessive amount of free space, (light load without any filler) the primer can spread and separate the individual grains of propellant and allow them to ignite simultaneously. This circumvents the "progressive" properties of the propellant and causes a very high pressure spike of short duration.
This is far less likely to happen in pistol ctgs.
But I have to quibble about your use of "progressive burning." Your description is not at all what a propellant designer would use. Rather, progressive burning means that an individual kernel of powder exposes more and more surface area as it burns, thus burning progressively faster until it is consumed. Extruded kernels with a deterrent coating on the outer surface and a microscopic hole through the center burn progressively because they burn from the center outwards. Powder that burns from the outside in (flake propellants are one example) burn REgressively because they expose less surface area over time. Powders designed to burn both ways are neutral burners.
What you say with regard to individual grains (flakes, spheres etc)being progressive burning due to increased surface area is true. But the progressive nature of the powder column as a whole is determined by the rate at which the flame front passes from ignition point to the last grain of powder. With small charges of powder in a more open environment, it is possible to ignite ALL of the charge at once. Ergo...BANG !
Rocky, in the loads you are referring to, the loading still has a density of 70% to 80% or better. (you can still hear it rattle) Loadings that are prone to detonation are in the 25% or less category. It is not so much the "available energy" as the rate at which it comes to bear that causes the damage. (aka shockwave)
Then there's the handgun aspect. Many handgun loads use only a pinch of very fast powder. The "flash across and light everything" model happens with nearly every shot from a handgun, yet no detonations seem to happen there with factory ammo. Handloads, yes; but as I pointed out, those invariably turn out to be double-charged or worse.
I'll go with what the real expert tells me, guys. The discussion is interesting but the real science of it is probably out of all our depths.
detonation occurs when the load density is far below that 1/2 way point, and the entire charge can be ignited as the flame jumps across it unimpeded.
that is why many of the catastrophic failurs pictured on the net, are from light loads and often people being cheap and trying to figure out how to make fast burning powders work in cases that are far larger than the intended cases for the faster powders.
As I said above, unless the case is 100% full, the primer explosion blasts all the powder around, driving flame, hot particles and highly compressed (hot) trapped air into every interstice between kernels. Almost all of it is exposed to temperatures above ignition temp on nearly every shot, and nearly all of it gets ignited every time. Only in long and thin cartridges will there be any differential between the rear and front of the powder column, and that is created by compression of the powder into a nearly solid plug.
The Secondary Explosion Effect is real, but it is due to other, much more complex causes than imaginary "primer flashover."
Might we be looking at a Crimp factor here ? Was it used in any of the known incidents ? If so,to what degree ?
Just asking..as I read the responses, I find my limite
In the history of SEE, it is most often seen when (and it was a fad in the 60's) trying to make light recoiling plinking loads for the big boomers. Example: 30 carbine level recoil in a 300 RUM case.
Above someone mentioned a 70% fill threshold, more often it was seen when the powder fill level was in the 20% (or lower) range.
Manuals offer you a starting point, and that level is well above what will cause SEE (there are some powders that explicitly recommend that you NEVER go below the manuals starting level)
as far as blasting flame into every millimeter of the case, and encompasing the powder 360*, that is not how it happens. The "burn rate" of powder is the exact caveat to that theory. Powders are listed by "burn rate", which means that applying any average tested brisance (the amount and lenght of time a flame comes out of the flash hole), the powder will burn and build pressure at the specified rate, in a given case capacity. By using powders far too fast for that given capacity, you change the pressure curve. A fast powder in a case too large will build pressure more rapidly than the surrounding metal can handle. When experimenting with light loads, especially in powders too fast for the case capacity, you are looking for trouble, or worse.
also, the only way powder and fire become compressed is the ignition of the powder charge, while the bullet remains almost still. The milliseconds during ignition create pressure as the load ignites, and the bullet starts to move. The majority of powder, burns in the barrel, not it the case. If it took place in the case, the cases would burn through in several firings. Brass is far less dense than steel.
There isn't space to counter all your incorrect points, so I'll just disprove the most comical of them. Powder lays like gravel? Puff some air at gravel, and then puff at some powder. The concept that powder just lays there while a small explosion blasts at it is ludicrous.
Unless someone has a cogent question for me, I'm finished with this thread. The positions have gotten implacable and unresolvable.
well Rocky, you're sure wrong there. Not only is it possible to see what takes place in a cartridge case at the time of firing, it happens as a step in production of large caliber munitions. Xray is used to expose the film used in ultra high speed photography. Ya can watch it all !
AND, the only way powder is puffed around, is if the load density is too low, leaving room for the powder to be blown around. When a correct load desnity is used, there isn't enough space for the powder to be "blown around" as there is maybe some 10-20% capacity left unfilled.
maybe this explains why there has never been a detonation in full or close to full cases[?] it only happens on light loads or light loads of powder too fast for that case size, it never happens when correct load density is used with appropriate burn rates. This is EXACTLY why the lawyers make the reloading manuals have statements about not going below the recommended charges, this way, when you blow the gun up playing with undercharged cases, they have no liability because they told you not to.
JustC, you brought up the supposed "flashover" with small charges, and I maintain that such a thing is impossible. In fact, what I call the "leafblower effect" would be MORE likely to over-ignite a small charge than a flashover where only the top of the powder surface is exposed. Yet, in 99.999% of times, such loads function normally. If small charges cause SEE events, they are darn poor at it.
BTW, on another website a guy reports that he blew up a Mauser in 6.5 Swede - with a nearly full charge of 4064. He weighed every charge TWICE and visually observed the powder level in every case before seating a bullet. So don't say a SEE has never happened with a full charge of slow powder.
Both these things reinforce what I've been saying all along: that SEE events do happen, but the popular "explanations" of what cause them are probably wrong. Something causes them, but we haven't yet learned what.
And here's a magazine writeup quoting an unnamed powder company ballistic lab. Both seem to confirm my major claims. http://africanxmag.com/secondary_explosion_effect.htm
hence my point
Another thing that was causing guns to blow up was in those large cases with light charges, they could be "double-charged". There is enough room to get two charges in the case and not really know it. So, when seating the bullet, no undue problems are encountered in bullet seating. But when fired, the gun comes apart
again, my point. Those who experiment with powders too fast for the case capacity, are asking for SEE. There is a clear cut reason that powders are listed by burn rate. They are meant for specific case volumes coupled with a particular projectile weight range. When using unsuitable powders, they are in the danger zone. If they double charge a bottleneck rifle case, with pistol powder, I would bet they couldn't look into the case and see the difference. Pistol powder loads would be around 10grs if double charged, and when the case will hold 80grs, they are wayyyy off into the playground.
He had another thing to add, and that was that S.E.E. does not just occur with "slow" powders, but can and does occur with fast powders as well. His experience has been with "Cowboy Action Shooters", who are loading small charges of fast powder
the article also doesn't state that this happens with full case loads of slow powder, a very important peice of info. I have run H870 and even 50BMG powders in a 300RUM. However I was using heavy 200+ gr pills and the case was FULL. What I got was reduced muzzle velocity and dirty cases, which is a sign of LOW pressure. Low pressure doesn't blow up guns, high pressure does. Now a light load of slow powder, with a spark jumping across it, I could see SEE possibly happening.
also remember, powder companies use what they call "test guns". These are large actions with huge barrels. The amount it takes to blow up a test gun as opposed to a hunting rifle, IMHO will be different. They really should include chamber pressure data with their load data, that would be a big help for the reloader. They have strain guages that they use in testing, so they should include the avergae chamber pressure with the load data. I for one, would appreciate that as a reloader. Also keep in mind, their barrels are far more quality that the factory pencil barrel.
not to say it is explained in simple terms, but eh large majority of SEE I have seen on the net, and posted by the owners over the years, are from someone messing with small charges of fast powders. Stick to the load manual suggestions. I don't experiment outside the manual, unless it is with heavy charges of slow powders pushing heavy bullets.
Terry is a very inteligent person as I have read his posts on another site for many years. I am going by the examples posted on various sites over the years, and the comments from the person who actually blew the gun up.
Thank you JustC, I feel vindicated.
Rocky, in the loads you are referring to, the loading still has a density of 70% to 80% or better. (you can still hear it rattle) Loadings that are prone to detonation are in the 25% or less category. It is not so much the "available energy" as the rate at which it comes to bear that causes the damage. (aka shockwave)
I agree with JustC. However, the loads you need to watch out for are not the 25% and below, they are the 25%-60% loads with slow powders. I have used 25% or less loads on a number of occasions to pop out a bullet stuck in the barrel from primer or super light load discharge. At that light of powder load the primer does flash across the entire powder charge and ignites it all. However, the reduced load doesn't give enough pressure to damage the gun. Only enough to remove the bullet from the barrel. Above 25%, and especially closest to about 50%, the charge can produce enough pressure to damage the firearm.
Rocky,
I don't know how you come to believe that smokeless powder in a contained case does not "burn" It burns just like a cigar...only about 21,000 times faster. Which as heat is released gives us that nice high pressure curve by which we can launch bullets. Because we contain that pressure momentarily in a brass case.
I can give you a like example of that in C4. I can take the same amount of C4 and in three different configurations, cut a tree in half, blow a hole through the middle of it, or detonate (burn at an extremely high rate of speed) it with minimal damage to the tree. It's because the compound burns directionally that I could do that. Smokeless gunpowder burns directionally, That's why we can use it to push bullets so fast.
Blowups in Cowboy loads are due to double-charging, not SEE. If the primer blast (it is absofrickinglutely not a "spark") across a light charge of fast powder causes SEE, then why DOESN'T it happen in thousands and thousand of handgun firings and almost all rifle firings?
Nobody here has yet explained how their pet theory does NOT cause SEE most of the time.
Oh, since we're tossing qualifications out there, I speak regularly with genuine ballistic experts in the small arms industry. Not nuclear energy, not military explosives and not "something I heard somewhere." I even eat lunch with them. NONE of them give the ideas here much weight.
Perhaps the enraptured members on this thread would like to learn how and why internal ballistics catastrophically blow out a revolver's cyclinder in locations ranging from horizontal-left, to various minutes of arc vertical, and to horizontal-right, BUT do not blow cylinders below horizontal. All photographs that I have seen of blown out cyclinders showed the damage at or above the horizontal plane, and not below the horizontal plane. Perhaps there is a scientific, ballistician's explanation for this observable effect. It appears that Rocky is more knowledgable than anyone else on this subject. I for one would appreciate learning the explanation.
It's because the strongest part of a revolver is the bottom. And, the weakest part is the top. If you look at the rifle that tailgunner put up you will see most of the damage went downward. Another picture a short while ago showed a rifle, a Mosin-Nagant I believe, that had the bottom blown out of it. That's where the gas and pressure is designed to go in case of catastrophic failure.
SEE involves a secondary explosion, generally thought to involve a reflecting and self-amplifying pressure wave within the case. The mechanism causing it is not understood, but the effect can be reproduced sporadically in the lab.
Another not well understood phenomenon involves a hang-fire, loss of propellant deterrent coating, and re-ignition at a greatly increased burn rate. This is what happens in handgun rounds using reduced charges of H110/W296. It is believed that the primer fails to generate enough heat and pressure for ignition, but does displace the deterrent coating. After a noticeable hang-fire of less than a second, the powder does ignite (probably due to still-incandescent primer particles) but without a deterrent coating, burns instantaneously. Here's a photo of a reduced H110 that fortunately did not re-ignite:
You can see the natural greenish-yellow of the propellant absent its darker deterrent.
Finally, there are over-pressure bursts caused by double-charges, wrong powder or foreign matter (like tumbling media) in the case. These are neither mysterious nor misunderstood: they are simple mistakes.
Revolvers lose the top three chambers and the topstrap mainly because the first chamber to burst directs its energy in all directions, but that energy is quickly dissipated. There is enough to burst the top chamber and peel away the two adjacent ones, but by then the pressure is exhausted. If the event were a true explosion, with supersonic shock waves, the destruction would be much greater. In fact, the classic three chamber burst is almost definitive proof that what happened was NOT a true detonation but only an over-pressure firing.
Here's another photo of one in action, for your enlightenment: