Reading a book on propellants and explosives, and the author claims that muzzle flash is mostly superheated gasses that have exhausted their internal oxygen supply, and which re-ignite when the gasses get into the normal atmosphere, which supplies new oxygen. Anybody ever heard this before?

I always thought as you pulled the trigger, you set off gases and pressure. That starts the bullet down the barrel, and hot gases expand as the bullet leaves the barrel. This causes a pressure wave in the air and that is what causes the bang or the noise of the gun. To that, all the powder behind the bullet is not always completely burned. Also when using faster burning powder's the less of a muzzle flash. I've seen some blinding flame thrower's using H-4895 52.5grs and a 150 gr bullet in a 30-06 with a 22in barrel. Also using H110-26grs behind a 240 gr bullet in a 7 1/2in Ruger Redhawk 44mag.

I wonder if there would be a muzzle flash on the Moon? The burning powder supplies its own O2 by means of the chemical reactions within the barrel.

But what happens in an absence of air?

Interesting questions.

Of course, a cartridge will fire in space, because it does supply its own oxygen.

According to the author, though, a lot of the muzzle flash happens when all the oxidizer in the powder is gone, and there is leftover combustible gas that has no access to oxygen until it exits behind the bullet.

It's a new idea to me.... just trying to get my head around it. I always figured it was just unburned powder. And I think it is true that you get more flash with shorter barrels and longer burning powders. So I wonder if the author's statement is correct??

The muzzle blast does contain gasses that have not fully burned. Sometimes unburned powder
ia also expelled. Gun "writers" will tell you that all the powder is burned just after the bullet starts
to move. Not quite right, they should say "all the powder that is going to burn".
The author (whoever it was) weas correct.
Good Luck!

Denton, yes that is correct . Somewhere in my books they mention that but I can't find it . Of course there are many variables , barrel length , type of powder etc and one of the mechanisms is to reignite the gases .This can produce an effect like a smoker blowing smoke rings and I have seen photos of this on large naval guns.

Probably has no bearing whatsoever, but it is interesting to note that when I lived in Florida I did two tanks per day SCUBA diving.

I loaded for BangSticks...in .44 Magnum and in 12 gauge. They both had "muzzle flash" in water as deep as 125 feet.

Smokeless powder is composed primarily of nitrocellulose, sometimes with a bit of nitroglycerine added (double base powders), but also contains several other organic chemicals. There is always a bit of residual solvent (perhaps 1-3% by weight), which will be ethyl acetate in Ball powders, or a mixture of ethanol and diethyl ether in IMR-type powders. Sometimes other solvents like acetone are used in applying deterrent coatings, and will still be present in small quantities in the finished powder. Deterrents can be of several sorts, some of which are themselves energetic (but oxygen-deficient) compounds like 2,4 dinitrotoluene (used on most IMR type powders), and some of which are "fuels" with no oxidizing groups in the molecule, like the dibutyl phthalate used on most Ball powders. There may be anywhere from 4-10% deterrent by weight in typical powders. Then there are stabilizers, like diphenylamine, 1-2% by weight. Some powders contain additional plasticizing or "gelatinizing" agents, like camphor (found in some Russian powders) or centralites. All of these are organic compounds rich in carbon and hydrogen with insufficient oxygen present to burn them. They all vaporize in the heat of the powder's deflagration and are present in the gas mixture produced. Nitrocellulose itself is oxygen deficient to varying extents, depending on the degree of nitration. The gases produced when it decomposes include carbon dioxide, water, nitrogen, carbon monoxide, and hydrogen. The last two of these are fuel gases. Nitroglycerine decomposes to carbon dioxide, water, nitrogen, and free oxygen, but it only releases a net amount of one oxygen atom per molecule of NG. NG is usually a minority component of powder if present at all, so even double-base powders are still quite oxygen-deficient.

Whenever a charge of smokeless powder is fired in a gun, this mixture of fuel gases containing the combustible products of nitrocellulose and a considerable amount of organic vapors from the solvents, deterrents and stabilizers (and compounds produced from them by thermal "cracking") is produced, and this flammable cloud blasts from the muzzle. When it does, it mixes turbulently with surrounding air containing oxygen. If it's hot enough and remains hot long enough for autoignition, this mixture can explode and make a bright flame resulting in a "secondary muzzle flash." This is the big showy bright orange-white flash sometimes seen. The primary muzzle flash is from the incandescence of the heated gases and suspended particles, like the little orange-red squirt from a shotgun or .22 rifle at night. (You would see that on the moon, but no secondary flash.) You don't always get a secondary flash, because the gases may already be cooled too much from expansion within the bore for igniting during the very brief time before they cool well below ignition temperature from further expansion and mixing with cool air, they may be rapidly cooled by being broken up into small jets by a flash-suppressing muzzle attachment, or they may contain flash-inhibiting substances like potassium salts (like the ~2% potassium sulfate found in IMR powders) that inhibit the free-radical chain reactions initiating the explosion. (This action is just like what tetraethyl lead did to prevent "knocking" in engines using leaded gasoline.) Other factors like the presence or absence of glowing sparks in the muzzle cloud can influence ignition, as well. Given the relatively small quantities of powder used in small arms cartridges, the delay time involved in autoignition of the gas/air mixtures, and the rapid cooling that occurs in the exhaust cloud at the muzzle, secondary muzzle flashes are more the exception than the rule (and can be quite entertaining), but they're a big problem with artillery. You'll see secondary flashes a lot more when using heavy charges of slow-burning powder, not because powder's still burning outside the muzzle, but because the gas temperature is higher when the bullet exits the muzzle with these loads. The solid powder extinguishes almost instantly when the pressure's released and contributes little to the flash. And individual powders will differ in their flashing tendencies due to differences in composition.

You keep this up and you ain't gonna be a new member for long. Keep your guitar strings tight, John. Have a great 2004. roger

Thanks, Roger, and a happy new year to you, too!