Is excess powder really blown out?

[Ron Nance]

Assume for a minute that powder burns at a specific velocity.

The velocity of the ball is determined by the amount of pressure created.

As the ball travels down the barrel the volume of space increases lowering the pressure.
if you add more powder to create more pressure to create a faster velocity, the volume related pressure drop will eventually out pace the velocity.

Why?

Because the velocity of deflagration (burning) is limited. (this is the fundamental difference between black powder and smokeless. Smokeless doesn't burn or deflagrate, it detonates.)


Powder only burns so fast, at some point adding more won't result in any projectile velocity gains.( Unless other things are changed.)

Artificer, I think you may have typed it backwards. BP is a explosive and detonates where as smokeless powder does not detonate and burns. All BP containers are marked EXPLOSIVE and in the stores must be stored in a bunker where as smokeless power is placed on the shelf in the open.

 

[smo]

Artificer, I think you may have typed it backwards. BP is a explosive and detonates where as smokeless powder does not detonate and burns. All BP containers are marked EXPLOSIVE and in the stores must be stored in a bunker where as smokeless power is placed on the shelf in the open.

Funny thing is the last case of Goex I bought didn't have the word "Explosive " anywhere on it that I seen...

I don't have the case now .....

 

[Artificer]

Artificer, I think you may have typed it backwards. BP is a explosive and detonates where as smokeless powder does not detonate and burns. All BP containers are marked EXPLOSIVE and in the stores must be stored in a bunker where as smokeless power is placed on the shelf in the open.

Hi Ron,

Black Powder is a low explosive and the technical term for its burning is "deflagration." Of course, since that is too difficult to type as often and many people don't know it, I use the common word "burn." High Explosives detonate, not Low Explosives.

The reason BP must be stored in bunker or special containers is because it is so much easier to ignite and at lower temperatures than Smokeless Powder. Just touching a spark or flame to BP will ignite it, while it takes more than that to set off Smokeless Powder.

Gus

 

[fleener]

Black powder is a unique product. It is listed by the USDOT as a 1.1 explosives. By definition a 1.1 explosives is "Consists of explosives that have a mass explosion hazard. A mass explosion is one which affects almost the entire load instantaneously."

For sporting purposes, the powder can be reclassified from a 1.1 explosive to a class 4.1 flammable solid. Most of us buy powder that has been reclassified to a 4.1 and you will not see the words explosive or an explosive label on your bp.

While virtually all 1.1 explosives detonate, and not deflageration, it is generally stated that bp is the exception to that rule and that it deflagerates.

Explosives start at 1.1 as the highest level and then goes down in classification as follows 1.2,1.3,1.4,1.5,and 1.6 that are explosives, extremely insensitive, no mass explosions.

Fleener

 

[Zonie]

Food for thought:

Black powder has an auto ignition temperature of around 870°F. or slightly less. When subjected to that temperature it will ignite.

A diesel engine compression ratio is usually between 15:1 and 23:1

Compressing ambient air to a 20:1 compression ratio creates a pressure of about 294 psi

Rapidly compressing the air to a 20:1 compression ratio will heat the air to around 1300°F

Notice, this 1300°F temperature only took a pressure increase of 294 psi.

The pressure in the breech of a muzzle loader can easily be over 2000 psi.

Now, I realize that in the case of a firearm, it really isn't compressing the gas from a room pressure of 14.7 psi. Rather, it is creating the gas from a solid but I have to believe the temperature of the gas is at least 1300°F or, more likely well over that temperature and this high pressure gas would have no difficulty in moving between the granules of powder and subjecting them to both the high pressure but the high temperature as well.

If this is true, the temperature around each particle will be well above the auto ignition temperature of black powder so, it will start to burn all by itself.

That would rule out the idea that there is unburned black powder in the barrel, even at the front of the powder charge well away from the powder that is actually burning at the rear.

(All of the data numbers are easily found on the web if you are wondering where I found them and yes, I used multiple sources to rule out incorrect values.)

Like I say, something to think about.

 

[Carbon 6]

If this is true, the temperature around each particle will be well above the auto ignition temperature of black powder so, it will start to burn all by itself.

.

Excellent hypothesis.
I think you left out one very important factor though.
TIME.
Deflagration happens in a fraction of a second, traveling at a velocity in excess of 2000ft per second.

I can quickly pass my hand through the flame of a torch without getting burned. I suspect the powder is more resilient, most people begin to experience pain from temperature around 120 degrees.

 

[BrownBear]

All makes perfect sense to me after what I've seen and tested.

One thing interests me. When you see slomo or freeze-frame images of a shot, you'll often see orange streaks to either side of the main flame. Looks like glowing embers if I had to make a guess. If I was going one step further down the guessing path, I'd guess those "embers" are partially burned charcoal or some such, perhaps helping explain the residue found on the ground from a heavy charge.

After my own collection of the stuff from three shots and attempt to light it, I was absolutely convinced that dearly departed Paul V was full of prunes.

 

[fleener]

The speed of sound is around 1,125 ft/sec. Deflagration happens at less than the speed of sound. Detonation is over the speed of sound.

Fleener

 

[Carbon 6]

The speed of sound is around 1,125 ft/sec. Deflagration happens at less than the speed of sound. Detonation is over the speed of sound.

Fleener

I did say can be.
The speed varies depending on conditions, and since we know it makes a sound we have established a lower limit. Which is still fast enough to make my point.
In a 28 " barrel at that speed the velocity of deflagration is about 2/100ths of a second per inch.
That's pretty fast for heat alone to cause auto ignition. However the heat does increase the velocity of deflagration.
Even if the powder auto ignites it still deflagrates. Black powder is a mixture of 3 ingredients that have different auto ignition temperatures. Auto ignition starts the deflagration it does not bypass it.

 

[zimmerstutzen]

Somebody mentioned looking at it by percentages. Well if I shoot 100 grains and get the figure I posted, then adding 30 percent more ought to result in 30% more velocity, energy, etc. Problem, it only boosts it by less than 1% 2037 fps to 2052 fps. Another theory disproven. The other thought mentioned was that all that hot gas seeps through the powder granules and lights them up. at what point does the gas from the rear of the charge push the unburned powder together like a wad ahead of the gas and only burn from the rear as it travels down bore. If we took a straw 10 yards long and packed it full of powder, would it all burn instantaneously or would it act like a fuse. We know that filling a powder pan on a flintlock can create a fuse effect. the imfamous click, shhhhhhhhhhhhhhh, boom. if the powder burns instantaneously, that could not happen.

 

[Carbon 6]

We know that filling a powder pan on a flintlock can create a fuse effect. the imfamous click, shhhhhhhhhhhhhhh, boom. if the powder burns instantaneously, that could not happen.

I don't agree.
The "fuse"affect is actually a Fuse like affect. A poor analogy.
A properly set up flintlock will not produce a "fuse like affect" Therefore the problem that causes it is not powder related unless the powder is fouled resulting in a hang type misfire.

Also you mentioned,

The other thought mentioned was that all that hot gas seeps through the powder granules and lights them up.

I guess I would add that that "hot gas" is actually on fire and close to 3000 degrees.

 

[Carbon 6]

A diesel engine compression ratio is usually between 15:1 and 23:1

Your engine reference reminded me about Rudolf diesel's attempt to run a engine on coal dust.
In the 1600's Christiaan Huygens experimented with an internal combustion engine that ran on black powder.
George Cayley designed a gunpowder engine for use as an aircraft engine in the early 1800's, it never got off the ground.
The earliest record of a gunpowder engine was a patent letter in 1661 that supposedly belonged to Samuel Morland.
There have been others but none have succeed. It's really quite fascinating.

 

[Sinner]

While "shooting in the dark" will do nothing to prove or disprove the question of unburnt powder, shooting over a sheet will. It is well proven that excess powder will NOT be burnt and will exit the muzzle. Now, you of unbelief can discover for yourself in a very easy manner. Go forth, and discover the truth!

 

[Carbon 6]

Unburnt powder or unburnable powder ? Big difference.

 

[Ron Nance]

Gus and Fleener, Thanks for the info and I stand corrected. I guess a old goat like me can learn a new lesson. Please, everyone have a safe and great New Year.

 

[azmntman]

While "shooting in the dark" will do nothing to prove or disprove the question of unburnt powder, shooting over a sheet will. It is well proven that excess powder will NOT be burnt and will exit the muzzle. Now, you of unbelief can discover for yourself in a very easy manner. Go forth, and discover the truth!

Brownbear did it for me (per 3-4th post on thread). Thanks Brownbear

 

[fleener]

Ron, not a problem at all. Hope you and yours have a great New Year as well.

Keep your powder dry.

Fleener

 

[Black Hand]

While "shooting in the dark" will do nothing to prove or disprove the question of unburnt powder, shooting over a sheet will. It is well proven that excess powder will NOT be burnt and will exit the muzzle. Now, you of unbelief can discover for yourself in a very easy manner. Go forth, and discover the truth!

With all due respect, you have made an assertion but have provided no evidence. By saying "well-proven", you imply there is evidence and therefore up to you to provide it (or at least a link or links to the evidence).

Also, what comes out of the barrel may be carbon ejecta that is no longer able to ignite. Yes, it still looks like powder but it isn't...

 

[Artificer]

Somebody mentioned looking at it by percentages. Well if I shoot 100 grains and get the figure I posted, then adding 30 percent more ought to result in 30% more velocity, energy, etc. Problem, it only boosts it by less than 1% 2037 fps to 2052 fps. Another theory disproven.

I’m sorry you did not quite understand what Spence and I meant about increasing powder charges as a percentage of the charge from the shot before. We never wrote nor meant a 30 percent increase in powder charge would give a 30 percent increase in velocity. So let me try it another way.

As already mentioned, increasing the powder charge does not have a straight line increase in velocity. Again, the higher quantity the initial powder charge was before you added more powder, the less increase in velocity you will see. So, when you add 30 grains to a 100 grain powder charge (for an increase of 30 percent of the powder charge) in a 28 inch barrel, you will not see a 30 percent increase in the velocity of the projectile. So why is that?

A part of the answer is there is not enough time the projectile travels through the short 28 inch barrel for the propellant gas to increase the velocity of the projectile, as there is when the same load is fired in a 42 inch barrel. The projectile starts out faster with the 30 percent increase in powder in the 28 inch barrel, but since the barrel is rather short, the propellant gas doesn’t have as much time to force/act on the projectile inside the barrel, and to speed up the projectile, in the 28 inch bore. This because the propellant gas force is lost as soon as the projectile exits the 28 inch bore. In a 42 inch barrel, the same projectile and load would allow the propellant gas to increase the velocity more than the 28 inch barrel.

The other thought mentioned was that all that hot gas seeps through the powder granules and lights them up. at what point does the gas from the rear of the charge push the unburned powder together like a wad ahead of the gas and only burn from the rear as it travels down bore. If we took a straw 10 yards long and packed it full of powder, would it all burn instantaneously or would it act like a fuse. We know that filling a powder pan on a flintlock can create a fuse effect. the imfamous click, shhhhhhhhhhhhhhh, boom. if the powder burns instantaneously, that could not happen.

BP in a priming pan is open to the air and thus the propellant gas has no partial container for the gas to push against the projectile (or anything else), as it does in a barrel. The “container” for the propellant gas in a barrel, of course is not a perfect container. Pressure is lost through the vent hole in a flintlock or the nipple hole in a percussion gun, but there is still enough of a container for the propellant gas to push the projectile down the bore.

A 10 foot straw packed with powder and ignited at one end, also does not have enough of a container to partially hold the pressure of the propellant gas. So it will take much longer to burn than powder in the partial container of a barrel.

As you already mentioned, igniting the rear end of a powder column in a barrel does not give as high of velocity as when the powder column is igniting in the center – where the powder burns both forward and back at the same time. So igniting the rear end of the powder charge in a barrel, gives you something of a fuse effect inside the barrel and slows down (a little) the burning of the powder column in the barrel.


Gus

 

[Artificer]

Gus and Fleener, Thanks for the info and I stand corrected. I guess a old goat like me can learn a new lesson. Please, everyone have a safe and great New Year.

Thank you for the kind words and a wish for a Happy New Year to you and yours, as well.

Gus