I'd be dying for a chemist or engineer to get into this topic.

Mostly internal ballistics is what I'm focused on. Of course you can take this anywhere you want to go.

Double based, single based . . . extruded, flake, and spherical. Most of that data is discussed in load manuals.

I understand that the powder is coated with graphite and that's what makes it black. What about "buffers" and "retardants" that affect the way the powder burns?

How can one powder produce higher velocities at lower pressures? How can the same powder then produce lower velocities at higher pressures with a different weight bullet --- this comparing two similar powders?

I'm not a chemist or an engineer, but I'd say it might have something to do with the volume of gas that different powders create as they burn. Burn rate and gas volume are two differnt variables that could enter into whatever the equation might be.

I'm no engineer but once this topic gets going I think it will be HOT> One discrepency in theory that I think about is my quickload program seems to say that some powders won't burn completely in some of the shorter (20-22") barrels. A writer recently wrote that's bull and that alot of times slower powders like re22 are plenty useful in shorter barrels. I think I believe the writer.
Come on guys---I know there's thoughts and opinions out there.............

I plan on verifying this with a call to Hodgdon or IMR, but...

In the newest issue of Handloader Magazine, John Barsness says that it's a "myth" that any modern smokeless powder doesn't completely burn in even short barrels. He says that even a magnum case full of RL 25 or IMR 7828, the powder will completely burn within the first 5 inches of barrel.

He claims that the flash we see at dusk is from the hot gasses igniting oxygen in the atmosphere, not from unburned powder.

FWIW

Dan Newberry
green 788

Well, actually, neither. No modern powder burns completely inside the barrel. You can't put enough oxygen in gun powder to complete combustion. The kernels might be turned into gas, but the gas doesn't complete oxydation until you add atmospheric oxygen. FWIW, Dutch.

I am not an expert but I do alot of reading on all of the reloading related subjects so please don't hang me if I'm off a little on this!
How powder burns is a function of a few variables. It really does not burn, it chemically reacts to the heat of the primer turning into a gas and rapidly expands. Major variables are single or double based, shape of the kernel (extruded , flake, ball, flattened ball), size of the kernel measured in total surface area, and retardant applied. A burn rate chart is a little deceiving because it really is not a burn chart, it is the rate at which the powder is able to turn from a solid to a gas. That is why two powders listed on the cahrt can not be interchanged and loads derived from the order of the powders on the chart. Extruded powders like those from the IMR series are actually designed to "burn" from the inside out. If you examine the kernels under a microscope you will see a hole through the middle of the extrusions with a majority of the retardant on the ouside and end surfaces so the first part of the kernel to ignite is the hole down the center. Flake powders are extruded but they are sliced thin and are designed for faster burn rates and lower pressure applications like those needed for shotguns and some pistol rounds. Remember, there are always exceptions but these are general rules. Flattened ball powders like those from Winchester are designed with burn rates that overlap a great deal lowering the need for many different powders.
Every powder has advantages and dissadvantages to them. The extruded powders can be designed for very slow burn rates but they won't flow through a powder measure very well making it necessary to hand weigh the charges. H870 is one exception as it is a ball powder. Ball powders will flow through a measure like water and that is the main reason varmint hunters that shoot 100's of rounds in a weekend will choose them to aid in the speed of loading on progessive machines.
The higher the pressure the more completely the powder will burn. That is why it is crutial to have a tight crimp while loading shotshell so the powder has a way to build pressures and keep the ballistics of the shells as close as possible. If a shotshell is loaded properly there should be very few flakes left in the barrel. There will never be a complete burn because the lower pressures of shotshells will not permit every single flake to ignite fully. There are some powders that are known as dirty powders but that is mostly due to the residue leftover from the "burning process". Some of the powders designed for loading trap and skeet shells are much cleaner due to the lower charge weights is each shell and their respective burn rates. Rifles develop pressures 3-5X of those found in shotshells which allows the powder to react completely and not leave unburned kernels in the barrel. If you can find the article by John Barsness (Handloader, June 2002, No. 217) he explains this very well and he is my favorite writer in the varios gun related rags I receive every month.
I hope this helps and I'm sorry I was so long winded but I don't know how else to explain this and black powder is another subject for a different day.
Elk Country

That's the source of the muzzle flash - oxygen finally reaching the super-heated but unoxidized products of powder ignition, after the bullet emerges from the bore.

Adding an oxygen catalyst to the powder within the cartridge case may achieve complete oxidation of all gas products within the barrel...but that'd also change the burn rate of the combustion reaction going on within the cartridge and bore. This is something the average handloader doesn't have the equipment or skills for monitoring safely.

TXLoader

"It really does not burn, it chemically reacts to the heat of the primer turning into a gas and rapidly expands."

Elk,

If you don't think powder burns, take a few grains and put them in an ashtray. Now strike a match and light them. Next poke your finger in there and get one of those grains on your fingertip.

I guaran-damn-tee you will believe that it does in fact burn, and it does so at 3,000 degrees temperature.

Been there, done that...jim dodd

Jim,

I knew someone would have a problem with that statement. In the open air where the powder can mix with the atmosphere it will burn, I do it all the time with unknown powder when I pull bullets. However, when the powder is enclosed inside a cartridge case sealed from the elements it is a reaction to the heat of the primer that changes the powder from a solid to a gas. When that hot gas exits the muzzle and mixes with oxygen in the air, most people think that is the powder burning but that's not the case.
The hot gas is now mixed with oxygen and causes the ball of fire called muzzle flash. The term burn is used loosely here because it's a term most people can relate to. I'm not arguing with you I am just stating how the powder reacts when confined in and out of a cartridge case.
Elk Country

[ 06-19-2002, 01:07: Message edited by: Elk Country ]

I also read the "Myth" article. Just for fun, on your next trip to the range set up a plain sheet of newsprint about five feet in front of you favorite rifle muzzle and fire through it. If you get a single hole for the bullet and zero "specks" then all of the powder was consumed before reaching the paper. If you get "specks" and little burn spots, the good fairy didn't put them there.
Second point, have you ever fired a pistol, revolver or semi-auto using Red Dot or Unique? Where did all those little semi-burned flakes come from? But, then again, I'm not a magazine writer or a chemist. I just shoot for the pure enjoyment of it.

I don't know how much time I am going to invest in this discussion but hear are the basics:

1. all smokeless powder is nitrocellulose based.

2. ball and other double base powders have nitroglycerine added (some as much as 10%)

If all smokeless powder is nitrocellulose (it is), how can one powder burn faster than another? Well, they blend retardents and buffers to slow powder flame fronts down. Powder in a cartridge burns due to a pressure wave that travels at the speed of sound within the medium of transport and the retardents slow the progression by making the fuel more temperature resistant which keeps the powder from igniting as easily - lowering the pressure / time curve which reduces the peak pressure and the pressure rise time. Buffers are used to lower the mean specific density of the propellant without slowing the burn. It is a little like taking sawdust and lighting it in a box and then shaking it up to mix the burning dust with the dust that is not yet burning - it flares up fast.

By the way the muzzle flash is the burned products of combustion at very high temperatures. Powder contains enough oxygen to burn completely without any additional oxygen - they test the burn rate in a CLOSED container (ballistic bomb) and it does burn completely in less time than it takes to push a bullet through a 4 inch barrel.

PaulS

Elk,

The powder is like rocket fuel: it has both fuel and oxidizer as Paul points out.

jim dodd

Does nitrocellulose burn? - depends on your definition of "burn".

Truely, it doesn't "burn" in what most people would define the term - a fuel reacting with atmospheric oxygen to produce heat, light, hot gases etc. It is a self-contained chemical reation that splits apart the nitrate groups (N03) that are attached to the cellulose molecule - then uses the freed oxygen to react with the carbon, hydrogen etc making up the cellulose to produce mostly heat, CO2, H20, and N2; with some ash made up of residual carbon and other compounds. The retardants and shape of the powder grains as well as the actual chemical makeup of the nitrocellulose (how many Nitrate groups actually did attach to the cellulose molecule during manufacture - it can and will vary just as the size of the cellulose molecules will vary) determine the speed of the reaction.

IMR granuals have a hole down the middle to try to even out the reactions speed - with just the outside burning to the middle of the grain the reaction would produce lots of gas at first due to the higher surface area of the full grain, then get less gas as the grain gets smaller due to the burning. With the hole in the middle, the surface area reacting stays more constant as the middle burns out as well as the outside surface burning in; giving you a more even production of gas. The very large granules used for artillary actually have multiple holes down the middle in an effort to make the powder "progressive" burning - i.e. the grain of powder produces MORE gas at the end of it's burning than it does when it starts. This is desirable as the volume containing the gas is getting bigger as the projectile goes down the bore - lowering the pressure. Having more gas produced at the end keeps the pressure higher longer, and at a lower peak pressure.

Retardants are used to slow the reaction down - either by absorbing energy used to split the nitrocellulose apart or by using up some of the oxygen with a reaction that produces less energy. They also produce ash as they are typically made up of metal compounds that don't produce gases in the reaction, but compounds that are solids. These compounds are used to control the overall reaction of the powder - the more you coat the powder with retardants the "slower" the powder reacts.

The buffers are used to change the composition of the resulting ash - changing a reactive residue like an acid to other compounds that won't harm the bore of your gun.

The major problem with nitrocellulose is that it will break apart under temperature and pressure - and react to produce more temperature and pressure. So you have a positive feedback, the higher the pressure you burn your powder at, the faster the powder will react and the higher the pressure wants to go. This is why the old pre-WWII powders had problems going above 50,000 CUP, and why modern powders have problems going above 65,000-70,000 psi. The predictablility of the reaction no longer holds and you can get MUCH higher pressures by adding just a few more grains of powder. It isn't that you add very much to the total energy contained in the cartridge, but that a threshold of control was crossed and your powder reaction speed greatly increased - resulting in a very high pressure that destroys your gun.

At the same time the use of retardants also causes misfires due to not having enough heat/pressure produced by the primer to properly initiate the nitrocellulose reaction. This is why you don't use light loads of slow single base rifle powders- you can't predict what is going to happen. You use a fast double base powder and have the nitro-glycerine carry the reaction to the nitrocellulose and insure that it will react.

[ 06-19-2002, 06:38: Message edited by: CMcDermott ]

"Quick start" and "push".

The bullet only stays in the barrel for so little time for gas to accellerate it. How do you manage to give it the most amount of energy during this small window?

A fast burning powder will give the bullet a "quick start", but the pressure rises so fast you will need to reduce the charge weight, thus there's not much "push" once the chamber reach its max pressure.

A slow burning powder will "push" the bullet for longer time but it can't provide a "quick start" due to its milder nature, but to take advantage of its nature you increase charge weight.

An ideal powder will start the pressure curve fast and the curve stays high. Progressive burning powder is closer to ideal than the above two.

A powder(no matter fast, slow, or progressive) can be found to work great in a specific chamber size and bore size ratio.
One that fits best delivers the maximum energy allowable by technology.
One that fits not so perfectly delivers not-so-optimum energy.
One that fits miserably...well, you know.

All powder granules will burn in a "well-thought-out" load. Back when I was trying to reproduce mil-surp muzzle flash in my Polish M44 I tried 125 grain bullets and 55grains of IMR 4350, I checked the bore after the first shot and there's about 30 sticks of powder granules lying in the bore. But with same bullet, 50 grains of H335 will spit fire and burn clean. No muzzle flash is to be seen with the IMR 4350 load despite the fact that unburn powder remains.

"Retardant" can be flash retardant or burning retardant.
"Buffer" can mean PH buffer, nitrocellulose and nitroglycerin both deteriorate and produce acidity which change powder performance and even cause danger of self-combustion. Urea and aniline are known PH buffers in powders.

I believe muzzle flash come from oxidation of unburnt "materials" coming in contact with oxygen in the air. Hot air does not glow, if you see some air glowing it's either having chemical reaction or being ionized.

A powder's burning speed is mainly governed by its grain size(surface area), perforation of the granule(if there's any) and the amount of graphite coating.

Does smokeless powder really burn? If something is bursting into flames we can call it burning, right?

Gosh you know they actually put lead soap in powders? Say it's going to make the barrel easier to clean.

From the way some of you guys like its smell there's probably weed in it too.

All I can say is this science of burning cellulose based nitro/ash particles (or whatever you are talking about) is so fun I can hardly stand it. I am just glad there are smart people like you to help us less scientific enjoy such a great sport by producing great powders like R22, and IMR 4831 and others.

I must add that this conversation is very interesting, even if I don't truly understand it. A buddy and me argued one time over this question that I think is relevant to the conversation at hand.

If you put a gun in a void (like space) and pulled the trigger, would the gun go off? Does the cartridge use any of the stored atmosphere trapped during reloading to help in the reaction needed to produce pressure? If you loaded the cartridge in a void, would the reaction be any different?

Fun stuff!

If you shoot a gun in a void, the cartridge will still fire with no significant difference in velocity/energy due to virtually all of the oygen source coming from nitrate (NO3-) and nitro (NO2-) groups in the propellants. If the cartridges were loaded in an inert atmosphere (ie. N2, Ar, etc.) then there would be a small drop in velocity, but then again, if fired in a void there will be no wind resitance in or out of the barrel. On the down side (for the environmentalists among us), loading your rounds in N2 will increase the number of polluting particulates (eg. R-NO and R-NO2) produced. However, the pollution produced from a day of shooting will not compare with the particulates formed by your car from your trip to the range.

Finally, I have had a chance to properly use my chemistry degree in this forum.

I'm a chemist, and I want everyone but Shawn not to feel bad, because they never covered much chemistry that happens at flame temperatures when I was in school. Generally, most of what they cover happens between the temperature where ice melts and the temperature where bacon grease starts to smoke. Am I right Shawn? I don't know what goes on inside the gun.

You do not need any air around to have a muzzle flash. Black body radiation is sufficient. Those gases that smokeless powder (or black powder for that matter) turns into are so hot, they glow on their own. Back at the cartridge case, the temperature is hot enough to melt steel. Anything at that temperature (even a cavity with nothing in it) gives off light.

H. C.

HenryC470,

I have some doubts regarding what you said : If black body radiation is enough to cause gas to glow, then why the tip of a candle flame(the hottest part) is non visible? H335 produce a lot of muzzle flash but W748 produces none, does that mean the flame temperature produced by W748 is way cooler than that of H335? If a gun produces muzzleflash with 18" barrel, but none with 26" barrel, does that mean all the gas cool down so much in roughly 0.001 second?

All the documentations I read regarding muzzleflash stated the muzzleflash being product of unburnt, yet combustable material oxidized by atmospheric oxygen.
I wasn't sure if what I read is totally correct, because at least I know hot object can glow , and they are neither having chemical reaction nor ionized.

What temperature DOES modern smokeless powder burn at? I read it somewhere but have slept since then and forgotten. I am thinking the gunpowder burns and 4,000+ degrees! I know one thing, it burns at a hell of a lot higher temp than it takes to melt steel, which I think is about 1,700 degrees.

Pyrotek,

My understanding of big muzzle flashes you get with different loads is imilar to yours. I think I remember reading that it was caused by unburnt Hydrogen igintin on contact with the air. That is possibly why some laods that produce big muzzle flashes often make a real heavy BOOM.

Mike

H.C.,
You are right about how chemistry is taught to undergraduates. Rarely will high temperature reactions be discussed in detail (except in physical chemistry and then few people can understand it!). Fortunately, I learned a decent bit about high temperature reactions in graduate school- including the use of pyrophoric compounds which burst into flames simply by coming in contact with atmospheric air! However, combustion reactions were covered in detail in classes pertaining to instrumental analysis, so I have a sufficient background in combustion chemistry to give an informed opinion. But, I am not an expert on combustion chemistry- my area is inorganic synthetic chemistry.

I believe that muzzle flash is caused by unburnt powder that ignites once it leaves the barrel. This can be tested by comparing slow burning powders versus fast. Cartridges that use very slow burning powder like 7.62x54R and 300 Wby produce huge muzzle flashes, while faster powder burns more completely while exiting the barrel and therefore, have less intense muzzle flashes. Of course, this will be hard to prove since two dramatically different powders would have to be tested in the same gun and fired at night.

Pecos45,
The temperature that steel melts at varies considerable with the alloy make-up. Pure iron melts at 1535 C (2795 F). The more carbon or molybdenum added, the higher the melting point. But keep in mind that the temperature spike from the burning powder is very short lived, so any melting of the steel barrel will not be deep enough within the metal to make any noticable changes to the structure.

Unfortunately, I was not able to find the temperature of burning gunpowder in any of my books.

In short, I believe that the occurance of black body radiation will play some role in the muzzle flash, but I feel that unburnt powder will make a much larger contribution.

I think that the hypothesis that atmospheric air contributes significantly to muzzle flash is easy to test (and wrong, but I'm willing to be convinced).

Put your 357 Magnum snubby in your shooting hand, put your hand in a clear plastic garbage bag, squeeze the air out of the bag, inflate the bag with nitrogen or better yet helium or argon (right Shawn?*), and then shoot with the gun in an inert atmosphere. Repeat the experiment, but inflate the bag with ordinary air. If you use helium, you should probably do the air experiment with the bag pointing upward (safety note added on reflection: that puts the gun in an upward attitude as well, not always a good idea), because that is the way the bag will point when it's full of helium. If the muzzle flash is substantially the same, then the mixing of unburned powder with air to combust in the usual sense is not a significant contribution to the observation of muzzle flash. If the argon-filled bag doesn't light up but the air-filled bag does, then your usual muzzle flash does involve the burning of powder in air.

This could also be done by rubber banding the bag to the end of the barrel, and I suppose you could even use the barrel itself to inflate the bag.

Caution! Do not go the next step and use a bag filled off an oxygen cylinder. Do not. You will at the least burn all the hairs off your arm. The plastic bag will in all likelyhood burn and melt all over you, and if you have on a long sleeve shirt, every part of it that gets permeated with pure oxygen will burst into flames.

Here is a brief discussion of flame, temperature, and light.

http://webexhibits.org/causesofcolor/3B.html

*What kind of metal complexes? We used to sublime ethyllithium and tert-butyllithium. They burn with a real pretty purple flame as soon as the air hits them. Trimethylaluminum burns good, but no interesting color.

H. C.

[ 06-23-2002, 02:51: Message edited by: HenryC470 ]

Hmmm, that sounds like an excuse to fill up Saeed's shooting tunnel with Nitrogen or helium.... Helium would be even better!

I want the video! With sound! . Dutch.

H.C.,
Your proposed experiment sounds intriguing. However, it might hurt the gun. I have an old Mosin-Nagant with a shot-out barrel that cost $40 that would make a good test case (plus it has a nice, long barrel to keep the muzzle blast away from the shooter). I don't know if the guys at the range would approve. Seriously, attaching a helium balloon to the end versus one that was inflated with a tire pump might do the trick. I still would not want to pull the trigger. Perhaps a long string attached to the trigger and an old tire to put the rifle in will do the trick. Then video the shots in the evening....

Greetings,
According to Vitavhouri, all the powder that is going to be burned is burned within a couple inches of the chamber. Of course some particles may not burn for various reasons.
Muzzle flash can be caused by many things. I do not believe it is due to unburned powder suddenly deciding to burn at release.
The very hot gases within the barrel cooling are possibly the reason for the muzzle flash.
When a chemical reaction takes place with sufficient energy , electrons are promoted to higher energy states around their atoms. When the electrons will fall back through the levels to their ground states they may release a photon. Depending on the energy level the wavelength of the photon is the color light we see. The wavelengths of visible light is roughly 425 to 720 nanometers. Since I generally see a yellowish flash this would be between 525 and 590 nanometers.
Gasses cool very quickly, sometimes I see a flash sometimes I do not, this can simply be due to very minor differences in the mass of powder burned and the temperature of the gas at release from the muzzle.

There are many types of chemical reactions; very fast as in the swapping of H atoms among water molecules (billion times per second) to the very slow, oxidation of iron (rust). When we see flames we have known since childhood this is "burning". Gunpowder does burn in the sense we can see the "flames".Temperature and pressure do increase the reaction rate (burning rate). Modulating the reaction rate is achieved as has been noted through the addition of various compounds to the nitrocellulose. Some speed it up, some slow it down.
Reactions can begin if their initial energy barrier is exceeded, this barrier is called the activation energy. As noted this can be so low that a reaction can be initiated at room temperature simply in the presence of oxygen. Once the activation energy is exceeded the reaction proceeds, if it is exothermic the reaction is favored and will proceed to completion.
Rapid reactions are difficult by their nature to quantify. We know if we take pure liquid nitroglycerin and add energy we get large volumes of gas and a great deal of heat given off very quickly. Exactly how the reaction proceeds is not too well understood due to its rapidity. This brings up another topic; what is combustion and detonation? A reaction that proceeds so swiftly that a shockwave forms that preceeds the reaction is called a detonation. An example is the nitroglycerin. The decomposition and recombination of the atoms occurs so swiftly as to be almost instantaneous.
Hopefully I am not rambling and this makes sense, it is kind of late here.

The only point I want to add to Roger's post concerns explosions. Theoretically speaking, they are fairly well understood. Explosions do not occur at a set reaction rate. Essentially, an explosive reaction starts with a very exothermic reaction with a reaction rate (say 100 s-1). The heat from the reaction causes the reaction to increase in speed to 1000 s-1. This in turn produces much more heat which then speeds up the reaction and so forth. As stated in Roger's post, eventually (within a fraction of a second) the reaction is proceeding so quickly that a shock wave is formed.

For anyone interested in reading scientific info on this, look for the book "Interior Ballistics: How a gun converts chemical energy into projectile motion" by E.D.Lowry. He was the Director of Research at Olin Chemical. He gets down to the molecular level of the burn reaction. Its an old book but the info is wonderful. Might have to check your library, I doubt its in print anymore.

I'm not a chemist, nor am I a gunwriter. But John Barsness be damned. He apparently has never fired a casefull of 7828 out of a 22 inch barreled 7mm Rem mag light sporter at dusk, and had a fellow shooter beside him shooting a 30" barreled target rifle in the same caliber and load. Now there is something coming out of that light sporter barrel that looks like something burning, and I'll bet if it was shortened to five inches, it would REALLY look like there was something burning coming out of that barrel..........bet it's powder............... Grant.