Reduced load blow-up's

[Andy Cross]

To make a long story short a friend last year blew up his .222rem. It happened when he wanted to shoot cast bullets back loaded a lot to replicate something along the lines of a 22 mag rimfire. I won't elaborate on why it was desirable to do this.

Can reduced loads really generate too much pressure because so much more of the surface area of the powder is exposed to the primer flash ? Sounds plausible. Would a slower powder solve the issue ?

Andy

[MilGunsmith]

Yes, thIs Is true. With reduced loads you need to keed the powder compacted down against the primer, at work we use cigarette paper. Trailboss powder is also usable due to the high volume to weight.

[alinwa]

I agree with milgunsmith about the Trailboss, this is what the Trailboss stuff is designed for. I probably don't agree with the cigarette paper thing but I'm not going to go there. I also disagree with your reasoning about primer flash but am not here to argue. Please just be careful where you get your info..... Making up your own reduced velocity loads is DANGEROUS in a way that many people don't realize. IMO much MORE dangeroous than oveloading beyond the recommendation in the manual. "Slower" powder IS NOT the answer, it's more complicated than that so please find a reloading manual and use listed loads to the letter. I've had this argument a dozen times because I jump up on my hindfeet and holler WHOAHHHHH!!!! I'll stay low on this one because the board is restless and I'm tired

I'm glad your friend is all right.

WEAR THOSE GLASSES PEOPLE!

al

[FBecigneul]

And here I thought it was because there isn't enough pressure to get the bullet out of the barrel before the gas is expanded and it blows back between the chamber and the case before the case neck can expand to send the gasses down the barrel chasing the bullet instead of back along side of the case in the chamber and out the bolt.

[Cheechako]

Reduced loads can wreck a rifle but it's usually with light loads of a slow burning powder in a large case. It's called SEE (Secondary Explosion Effect). Since no one has been able to produce it on demand, in a lab or not, there is no acceptable answer as to why it happens.

A light load in a small case, such as you described, does not fit the pattern of known examples of SEE. Without having the details of the accident it would not be wise to speculate on what caused it. Very light loads, trying to push a cast bullet at very low velocity is not a good idea and that alone could have resulted in a bullet stuck in the barrel followed by another, and kablooey! That's just one scenario. FBike's is another. Al is right. Until your friend knows exactly what happened it would be smart to discontinue the experiments, assuming he has another rifle.

Ray

[Boyd Allen]

What powder did your friend use?

[jackie schmidt]

This phenomina has been discussed for decades, It seems Elmer Keith had at least one article every month in Guns and Ammo about it, such noted Rifleman as Nidener, Ackley, Roberts, etc, would often comment on the dangers of shooting reduced slower burning powder charges in cases, resulting in a castastrophic event.

By slower burning powder, they mean a powder that would normally be a full density charge, such as 4831 in a typical 30-06 load. 4198 would probably fit the bill for this occurance in a 222.

The problem was, nobody could ever duplicate it in a lab setting, and many tried. I can vaguely remember on particular test back in the 60's, a lot of time and effort was spent trying to achieve results that many had heard of happenning.

To this day, I do not think that anybody has managed to duplicate the phenomina, that being, shooting a reduced charge of a powder that would be considered standard for a given case, and having that case blow up.

The speculation was, and still is, detonation occurs rather than a true 'burn'. The old cure was to fill the air space in the case with COW, or "kpock" which I suppose is some sort of wadding.

If old Elmer Keith were still alive, he would be jumping on this report like a duck on a june bug.........jackie

[Andy Cross]

Hi Boyd,
If my memory serves correct he was shooting 50gn cast bullets with IMR 4198 powder. Not sure how much but was around the 8 to 10 grain mark. Apparently he had shot this load before successfully but on that particular day boom. Which means as others have said it seems unpredictable. He weighed all his charges and seated the bullet straight away So it is unlikely that some got more than one charge. The cases were quite new so it wasn't likely to be brass failure.

Andy.

PS He was ok shaken and stirred.

[JD Mock]

A friend of mine blew up his Panda 6PPC while fire-forming brass at the SS. He had left some grease inside the neck and failed to get a full charge of N133 in the case. The brass had the necks turned to allow plenty of clearance. George Kelbly had to get the bolt out in his shop and the action was completely ruined. George concluded that it had to be detonation caused by a light charge. This is the first time that I have seen it happen, but evidently it can. James

[alinwa]

This is off the subject but I want to share it in the hopes of making this subject more clear, or in the hope of SCARING someone into not trying it on their own.

I live on a remote property. I have a kid who likes to blow stuff up even more than I do.

And he's better at it than I am, that's saying something.

He's built/brewed/synthesized every explosive compound you've ever heard of and thrice't that that you haven't. From his perspective he's breaking chemical bonds and converting mass to produce force and heat. A fire does this. An explosion does this. Both produce force and heat but not at the same rate, the difference between the controlled burn of a cartridge (deflagration) and an explosion (detonation) is composed of TWO parts..... the obvious one is SPEED of the reaction and the other is YIELD. High speed and a good yield produces a fast reaction, a CRAAKKK as opposed to a BOOM.... (I generalize.) The type of reaction dictates the yield which in simple terms is the amount of mass, the PERCENTAGE of mass converted. When a high percentage of the available fuel (mass) is converted you get lots of work done with little mass.

Get TOTAL conversion and you rule the world. (E=MC squared)

Generally you get higher yield from detonation than from deflagration.

Guns are nothing more nor less than internal combustion engines, they're designed to contain deflagrations not detonations.

And gunpowder CAN be made to detonate. I didn't know this. My kid stuck a blasting cap into a pound of old nappy smokeless powder.... wwHHOOOWWAAAuugghhhhhh!

Serious yield!

Another name for the SEE mentioned is detonation. For some reason tiny charges sometimes seem to detonate. And it ain't like a case failure, these detonations take stuff apart.

Jackie nailed it, especially the part about my hero Elmer

al

[Stonewall]

Norma has specific warning in the Norma loading manual on reducing powder charges below those loads listed.
Some powder-bullet combinations have only one load listed- not to be changed.

More information would really help understand just what did happen to your friend .

al that might not be "off topic".

Glenn

[John Kielly]

I flicked back to .222 loads in one of my old reference books, The art of Bullet Casting from Handloaders & Rifle Magazine.

There wan't much interest 20 odd years ago in loading the .222 with cast, but the loads recommended used Unique, 2400 & 4227, all powders a tad quicker than 4198.

[243winxb]

http://firearmsid.com/Feature%20Arti...wder/index.htm Many safe ways to make reduced loads in firearms. The Hodgdon website lists 2 of them. Trail Boss powder & Youth loads using H4895. Then there is Lyman info on using pistol powders with cast bullets. All very safe methods of reducing velocity & recoil.

[alpacca45]

There is some pretty sound advice on reduced loading here: http://www.guns.connect.fi/gow/gunwriters.html, Just scroll down to the picture of the Late Peter Kekkenon with a blunderbuss.

I go of on a bit of a tangent in what follows, but it does return to guns, so stick with it. Here's my pet theory, with the supporting facts first:

As Al has said, the difference in effects between deflagration (burning) and detonation is down to the rate at which energy is released.

Put crudely, this is known as "power" - the rate of doing work.

If I can release the energy twice as fast, I have doubled the "power". The Quarries that I do work for will typically fire about 15 tons of explosive in a blast, With delays between holes to reduce the vibration levels, that is still giving about twice the power of a Saturn V rocket taking off, for about half a second!

As the previous replies have said, we don't know the exact mechanism which causes a usually predictable and slow burning powder to "detonate".

Deflagration (normal burning) progresses from the exposed surfaces of the powder grains by heat conduction.

Conduction is a slow process, think of how long it takes from the time you pick it up for the heat of a paper cup full of hot coffee to conduct trough the 1/16" or so of skin on your finger tips, so you have to put the cup down again.

Obviously heat gradient and the contained heat energy have a bearing on this too.
I'm quite willing to pick up red hot wood sparks with my bare fingers and throw them back into the fire, but I certainly wouldn't touch a glowing spatter from welding!

Never the less, the process of conduction is slow compared to detonation.

Detonation has the material turning to gas at a reaction front which travels through the material at the speed of sound in that material.

In granular solids, like smokeless powders, that is measured in several thousands of feet per second.

Sonic velocity in a material is proportional to the density (and in solids to the stiffness as well) of the material. References which describe glycerine tri nitrate as "a dense liquid", as though that were somehow un related to it being a particularly powerful explosive are missing half of the reason why it is a powerful explosive.

It's an explosive because it contains a lot of stored chemical energy, which is released when it burns, but it is a "powerful" explosive because that high density allows the reaction front to travel much faster than it would in a less dense medium.

Explosives also suffer what is termed "dead pressing".

If the density is too high, they won't detonate.

There is also an effect in weaker explosive, where a cylindrical charge has to be a certain minimum diameter before a detonation will manage to run allong it.

You see both of these effects as limitations in the ammonium nitrate - fuel oil explosives used in mining and quarrying: Dense emulsions and slurries need to have glass spheres, perlite or polystyrene granules included to reduce their density below the point of dead pressing, or they just won't go off.

You also see the problem of minimum diameter, prilled anfo explosives generally like to be in columns a few inches in diameter, otherwise you tend to get squibs.

I suspect that both of these effects are due to energy being bled away from the detonation front.

Nitroglycerine has a lot more energy per pound than most other explosives, so there is plenty of heat in that reaction front to keep the detonation going, despite the high speed that the shock wave can move through the material.

I suspect that in less energetic explosives, that the effect of dead pressing is due to the shock wave being able to outpace the chemical reaction, allowing the energy to run away from where it's needed for the reaction to continue.

Introducing voids, reduces density and so slows the sonic velocity and stops the shock from running away ahead of and outpacing the chemical reaction. (there is also the side effect of the gasses in the polystyrene beads flashing to white heat as they are compressed by the shockwave, and giving additional points of initiation).

The minimum diameter problem, is I think also due to shockwaves bleeding energy away from the reaction, through the host material. This affects prilled anfo in rock blasting. The sonic velocity of the anfo is around 3,000 feet per second, the sonic velocity of the rock is anywhere from around 6,000 for crappy broken stuff, to about 30,000 feet per second for really solid stuff like rocksalt or anhydrite, and really good granite or dolerite.

Back to guns.

Factors that seem to have favoured detonation seem to be:

• relatively large case capacity
• Relatively slow burning powder
• much reduced load

Larger case capacity gives reduced surface area relative to volume for quenching to occur in.

Relatively slow burning powders are in larger and denser and much harder to ignite grains than the porous or flaked grains of fast pistol and shotgun cartridges.

There you have two of the factors from my theories about how detonations progress or fail to.

The third, reduced loading, I don't really understand.

My pet theory is that the layer of heavy grains of slow powder lying in the bottom of the case, only gets warmed by the flash of hot flame and particles from the primer passing above it, rather than having the primer flame pass through the voids between the grains and bathing all surfaces of the grains.

My guess it that that may set the dense (so good conductor of heat away from the flash) powder grains cooking, and decomposing without really taking light - sort of like a barn full of wet hay heating up.

My guess is that over several miliseconds or more, that this fills the case with hot gas and it consumes any deterrent coatings the grains may have had. eventually, like the barn of steaming hay, the whole thing takes.

My guess at this point is that the process is maybe a bit more like pinking in a gasoline engine, that the detonation shock wave is propagated through the hot gas, rather than through the solid powder grains.

The cooking will have removed the deterrent coating though, so any burning of the powder will be much faster than if it had started burning properly, heat conduction will also be much faster due to the rapid pressure and temperature rise with the gas detonating.

That's my guess for why "detonation" is more likely with a big case and a slow powder.

By "Big" and "Slow", I've read accounts of KBs with .300 whisper(tm) and Win 296, though the question of squibs arises:

296 is a hard powder to ignite - check out all the unburned grains you get with it! I'm not sure that with a low recoiling and quiet round like the whisper, the firer would necessarily have recognized a squib and the bullet stuck a few inches up his barrel.

Anyhow, fast powders are easily lit, and seem to be the ticket to safe reduced loads.

Alternatively, get a pistol calibre carbine and remove the big capacity case from the equation

[buffalobob]

here wan't much interest 20 odd years ago in loading the .222 with cast, but the loads recommended used Unique, 2400 & 4227, all powders a tad quicker than 4198.

Locked my bolt up badly with 4227 and a reduced load in a 7mm Wby. I ventured outside the recommended limits with it. Totally my fault for going beyond the recommended limits.