Home Forums Hunting & Shooting Ask The Gunwriters Ken! I must have been out of the room when they explained muzzle flash...help!

I'm almost embarassed to ask this but could you talk to us about it? What causes it? Can you do anything to reduce it? What characteristic of a powder effects how much or little occurs?
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Not too long ago John Barness (not one of our deeper thinkers) wrote in Rifle "The hot gasses burn up the air because everything burns better in air". I wrote him and asked if oxygen oxide was formed when air burned. So far he hasn't answered yet. The flash is caused by unburned gas (the process is oxygen poor). Unburned gas , and sometimes powder are expelled. How they treat the powder to minimize this I cannot answer. O K Shooter thinks that air space in the case will aid combustion. As you load from almost a case full to a full case the velocity passes through a "flat spot" where the relation of charge to velocity is not constant. I have seen similar results, but don't know if I agree with him.
<br> Now that I've answered this perhaps someone that knows more about powder will pick up on it.
<br>Good Luck!

I believe that that rate of burn also has a lot to do with it. I'm no expert, but I know that particularly with shorter carbine length bbls, muzzle flash can be reduced by using faster powders.
<br>badger

irv......I realize that the combustion of powder is never complete in a rifle and that the powder that does burn is combusted before the bullet travels very far down the barrel but I'm not sure what you mean by "unburned gas"?

Bill,
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<br>The way may chemist wife explained it to me is that smokeless powder has oxygen "in the mix", sufficient to create the rapid burning.
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<br>However, there is not enough oxygen in smokeless powder to COMPLETELY burn the powder. Adding atmospheric oxygen at a point where the gas is still hot enough to continue to reaction will complete the combustion. FWIW, Dutch.

I believe Dave Scovill answered your letter, and quite well. He sent me a copy of his answer, so I didn't bother.
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<br>Tests done by Homer Powley have shown that all the powder does burn within a few inches of the chamber, and except for a few non-burning solids (such as deterrent coatings) is completely consumed shortly after the pressure curve drops.
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<br>Muzzle flash is caused by the hot, still-expanding gases re-igniting when they hit the atmosphere, not by still-burning powder granules. You can blow unburned powder granules out the muzzle, but generally not unless you're shooting a cartridge operating at much lower temperatures than the powder was designed for. When loading the .45-70, for instance, with IMR4895 to 25,000 psi or so, you'll find unburned powder both in the barrel and on the ground in front of the muzzle.
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<br>But the granules of IMR4895 (or H4831) are all burned up within a few inches of the chamber when fired in a .30-06 or any other modern bottleneck cartridge that reaches 50,000 psi or more. Slow powders create more muzzle flash because the gases expand slower, leaving more hot gas to create more muzzle flash (and more muzzle pressure). But the flash is NOT created by still-burning powder granules.
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<br>An interesting sidelight to all this is that many tests (mine included) have shown that faster powders do NOT result in higher velocity in shorter rifle barrels, at least at any legal barrel length. The same powders that obtain the most velocity with a 24" barrel will obtain the best velocities in an 18" barrel. If you want to "retain the most efficiency" from a short barrel, use heavier bullets with slow powders. You'll lose less velocity with that combination than any other.

Hey Irv...Did we tell you that John Barsness is one of our valued members
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<br>Uhuh..Uhuh..Was that the left foot or the right?
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<br>Mike

A few more details, for anybody that's still interested.
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<br>About 30% of the gases flying out the muzzle are CO and H2, both highly unstable and desperately in search of oxygen molecules, in order to become the standard CO2 and H20 found in our atmosphere. But before they leave the muzzle they're simply part of the package of expanding gases, the powder burn long since complete.
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<br>The expanding gases do retain enough heat, however, to reach the flash point when striking the oxygen of the atmosphere. So when the CO and H2 leave the barrel they do oxidize ("burn"), and quite rapidly.
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<br>And yes, there's enough oxygen in the powder for it to burn completely inside the barrel.
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<br>I simplified all this, perhaps a little over-much, in my article in RIFLE, because most readers don't buy it for a chemistry lesson.

Here's Homer Powley's eleventh Technical Memo, "Muzzle Blast," from December 1963 -- the whole thing, more or less as it will appear in the book-form collection of Homer's TMs when I get it all put-together and publish it, as he requested:
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<br>You probably don�t know where most of the noise of a gun comes from. You have read about gases rushing out of the muzzle rapidly and then, with high-velocity guns, the formation of a shock wave by the bullet; these two things make noise. If you don�t know what a vacuum is, you might believe that there is a vacuum in the barrel after the gases are gone, so the collapse of the vacuum makes the noise; don�t believe this one.
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<br>In addition to noise from gas and bullet departure, there is a muzzle blast that makes most of the noise, and you can many times see it because of the flame. With large rifles, the noise is not a sharp, annoying crack but rather a slower �boom!� Just a few hundred yards from the gun, this is about all you hear unless the bullet passes very close to you, when you also hear the crack of the shock wave before you hear the gun. From a distance, the boom of a large rifle seems to lose direction. This is the reason that near settled communities, large rifles, unless very close, are not as annoying as small rifles, handguns, and shotguns.
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<br>Most practical rifle shooters know about muzzle blast, and a few of them know that unburned powder can be found on the ground a short distance from the muzzle. These few have then jumped to the conclusion that since not all of the powder has burned inside the barrel, it is burning outside the muzzle, and this is where the blast comes from. Don�t believe this one either.
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<br>With normal loads, only about 99 percent of the powder burns inside the barrel. The rest goes out the muzzle in the form of splinters � you can tell when you find them. All of the powder that is going to burn has done so at the place of peak pressure, which is only a few inches in front of the chamber. Some experimenters have used small cannon powders in rifles where only a low pressure (and velocity) develops, and unburned powder in the form of thin-walled tubes can be found, not only spitting from the muzzle but also trailed down the bore and left inside the case. In either case, powder burning in front of the muzzle can make only very slight noise.
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<br>When gunpowder burns under pressure, the solid is converted to a mixture of gases including nitrogen, steam, carbon dioxide, carbon monoxide, hydrogen, methane, free carbon (and from black powder, hydrogen sulfide). All of these � except nitrogen, steam, and carbon dioxide � undergo combustion in air. The relative amounts formed depend upon the kind of powder, the temperature and pressure when formed, the presence of catalysts, and the variations during expansion down the bore. They react with each other to change the composition. For example, carbon dioxide and hydrogen combine to make carbon monoxide and steam � this is known as �the water-gas shift reaction� and is reversible.
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<br>When these gases come out of the muzzle at high temperature and pressure, they ignite in the air to cause a secondary explosion by combustion and with the formation of a ball of fire. Most powders contain salts of some kind to reduce the blast and flash. An attempt is made to control the carbon monoxide if a gun is to be used in a closed space. Muzzle brakes or flash-hiders tend to spread the gases into cooler air with dilution and so reduce the effect.
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<br>So now you know.

It's nice to know that John is here, he can use all the help he can get.
<br>Good luck!

I have to admire a gun writer who will go online. It would be so easy to just hide behind an editor.
<br>Mule Deer puts it on the line and stays in touch with
<br>the real world.
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<br>Just seems like there is always a punk out there that
<br>has to show up in town with a chip on his shoulder and
<br>take pot shots.
<br>People like this cast a small shadow.
<br>Do you feel sorry for them Ready? I don't.
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I don't either and I would be pretty ashamed to type something I would't say in person. Man to man.
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<br>Mike

Re: Irv
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<br>I agree, and you note how brave he is to post his email address and location in his profile. NOT.
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Any gun writer who lets himself be surrounded by the opinionated ignorant -- and dares to "let it all hang out" where anyone can take a whack at him -- needs more than just help. Especially when he hides nothing -- name, location, e-mail address, whatever. I continually wish that my sense of candor and duty had let me be even more discreet about my own identity and access than my friend and colleague John is about his.
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<br>Now how d'you s'pose I know that? [vbg]

Thanks, Ken, both for your comments and posting Powley's quote. Hope you are doing well!
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<br>Over the years have received lots of fine correspondence and even phone calls from readers. It's very rare to meet a sorehead, thought they do exist. In general have found that if somebody really wants to track you down, they will, and since the readers pay my salary anyway, am always glad for any sort of dialogue.
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Mule Deer; It seems to be time to set the record straight.
<br> Scovill did answer my letter to you. In it he said that "there are no unburned gasses in the muzzle blast". This was in support of your statement that it was the air itself that was burning. No wish on my part to start a p-contest. but there is a lot of bad science quoted in regards to shooting.
<br>Good luck1
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Irv--I don't want to start any sort of contest.
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<br>I agree that there's a lot of bad science in gun writing. One of my specialties is testing accepted "facts," such as the myth of 30mm scope tubes providing a brighter image. I am also not exactly ignorant of basic chemistry, since I majored in biology at the U. of Montana.
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<br>My points about powder consumption in the HANDLOADER piece were two: faster-burning powders don't provide higher velocities in shorter barrels, and muzzle flash isn't caused by unburned kernels of powder.
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<br>I checked the article and the "quote" you cited earlier in this thread doesn't appear anywhere in the text. What appeared in the magazine is this: "So what's that big muzzle flash produced when we touch of a .300 Weatherby in the gloaming? No, Viginia, it isn't unburned H4831. Instead, it's hot powder gas lighting up the oxygen in the atmosphere. Add oxygen to any flame, and it burns hotter." I could have been a little more technical, and said, "it's hot powder gas lighting up when IT MEETS the oxygen in the atmosphere." How's that?
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<br>As I remember your letter to Scovill, you also contested the statement that the powder burns up about the time the pressure curve drops, in the first few inches of the barrel. Research (including Powley's) has proven this true. In fact, some handgun loads burn up their powder in the first half-inch. That's why Scovill stated that there are no unburned powder gasses in the muzzle blast. The gas is merely expanding, not burning. It's hot, yes, and it re-ignites when meeting the atmosphere--but the original burn occured way back down the barrel.
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<br>Am perfectly happy to have my writings criticized, but much prefer the critic to have their facts (and quotes) straight.
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<br>"Mule Deer"
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John, ol' Pard, re your " ... testing accepted 'facts,' such as the myth of 30mm scope tubes providing a brighter image," I have a wonderful old instrument for directly measuring the de facto brightness of a scope's image, if it'll help you test your scopes' brightnesses. It's a classic English SEI Photometer -- (Ansel Adams put me onto it, and though it was terribly expensive for a young biologist in the 1950s, I finally got one) -- a portable optical densitometer. It is, I believe, the original and still most accurate spot meter. The center spot in its wee telescope covers about one degree of angle (IIRC) and reads an amazingly wide range of brightnesses very minutely and accurately. (Clear down to the shadow under a piano keyboard in a dimly lit lounge, for example)
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<br>I've rigged-up a long Weaver base, with the saddle parts of two Weaver rings, to mount atop a tripod and hold a subject scope aimed at a white card. Back-to-back readings with the photometer -- one through, one over or beside the scope -- give a direct comparison of the brightnesses seen by the unaided eye and through the scope.
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<br>If it's worth a trip to Stevensville to try it, you're welcome. I'll even put you up overnight -- in somewhat less than regal comfort, unfortunately -- if a one-day trip won't be enough to get the job done. [406] 777-2878

Thanks very much for the offer! Can't make it until after hunting season, though, which looks like it will extend into January for me this year.
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<br>You brightness testing system sounds interesting, but according to all the optical engineers I've consulted, photopgraphic light meters don't work very well for telescope brightness tests. The big problem is their small field. If held close to the ocular lens, you're only testing the brightness through the center of the optical system, not overall brightness. If held farther back, at the apex of the exit pupil, ambient light from the side interferes with the reading.
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<br>In optics labs they use a different setup, a big sphere painted white inside and lit very brightly, called an integrated or intergrating sphere. The objective of the scope to be tested is inserted into a close-fitting tube in the side of the sphere, and a wide-lens meter fits tightly on the ocular end.
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<br>The light entering the scope is extremely consistent, and all the light leaving the scope is measured without interference from outside light. Have observed these are both Leupold and Zeiss labs, and they will measure transmitted light down to a tenth of a percent. But they're a little out of the economic reach of the average gun writer!
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<br>Actually, proving that 30mm tubes don't transmit more light was simple. The theory promoted by some people(primarily salesmen) is that the bigger tube allows the use of bigger lenses, which allow more light through the scope. The flip side, of course, is that a 1" tube somehow reduces the light, through mechanical constriction.
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<br>If this theory were true, the exit pupil of 30mm scopes would be bigger. This is easily tested by measuring the exit pupils of two scopes of the same magnification and objective-lens diameter. I did this with several pairs of similar scopes, and found that the exit pupil was exactly the same at the higher magnfications, regardless of whether the scope had a 30mm or 1" tube.
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<br>Only at magnifications under about 5x (depending on objective diameter) did the 1" tube constrict the exit pupil. At those magnfications, however, the exit pupil was typically at least 8mm in diameter, even in 1" scopes, more than the human eye can use. So there is no optical advantage in 30mm tubes.
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<br>Tests in integrated spheres bear this out. The only real advantage of a 30mm tube is a greater range of scope adjustment--but only lenses for 1" scopes are used. Several of the 30mm scopes on today's market use larger lenses, and have even less adjustment range than 1" scopes from the same companies.
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<br>We seem to have strayed from muzzle flash into optics!
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Luckily we really have no "topic police" here and it would be a shame to have to try and start a new thread every time someone mentioned something a little differant within a thread anyway.
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<br>many thanks to all the participants in this thread. I have learned many new things here.
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<br>Sooooooooooo..... I have one last question and let me make sure everyone here knows it is a question.... as I do not in any way pretend to be an expert on these matters.
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<br>I have owned a couple 30-378's with what Weatherby described as a 28 inch barrel. But with the brake it was more like 26 inchs of barrel really in my eyes. When fired at night it was awesome (and scary the first time) to see flames literaly burst out of the muzzle brake. I mean serious fire here guys! From reading magazines I always assumed this was because they always said you needed a 28 inch barrel minimum to burn all the powder from the large case on the 30-378. Now I assume from this thread that it would of probably had flames come out the muzzle brake when it hit the air even on a much longer barrel.... lets say just for this conversation it was a 32 inch barrel. Is this correct?
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<br>Again... You guys are awesome and thanks for hanging around here and putting up with what must at times appear to be silly questions.
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<br>Tex