Black Powder Burning Rate

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  • Last Post 12 April 2019
beagle6 posted this 11 April 2019

Does anyone know where black powder falls on the burning rate chart? A lot of folks think that it burns faster than smokeless but i am under the impression that it is very progressive burning. I also think it burns at pretty much the same rate whether confined or not. I'm sure there are members of the CBA who know the truth.

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JeffinNZ posted this 11 April 2019

It's a bit more complex than you might think.  To begin with we must consider grades of BP eg: 1Fg, 1.5Fg, 2Fg, 3Fg, 4Fg.  Next the variation between brands eg: Swiss is MUCH more energetic than GOEX etc.

Cheers from New Zealand

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beagle6 posted this 11 April 2019

Jeff

After shooting 10 years in the North-South Skirmish Assn, I definitely agree that Swiss has a lot more energy than GOEX. Costs a lot more too! What I was really refering to was the use in cartridges which I would guess to be about 1 1/2 F or there abouts. I would guess that something like Bullseye would slug up a lead bullet more than 1F or 2F Black.

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Maven posted this 11 April 2019

To reinforce beagle6's point, from another forum, take a look at this:  http://americanlongrifles.org/forum/index.php?topic=53705.25

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RicinYakima posted this 11 April 2019

beagle6,

"mad monk" on the before mentioned link, has the simplest answer. Black powder is nothing like smokeless powder. Black burns at "X" speed and the only thing you can do is play with the proportions of the mixture and the size of the granules. Smokeless burns faster and faster the more pressure it is under.

I think what you are observing is that it is "progressive" in pressure rise in a firearm barrel. That is because it only burns at one speed, so you want more pressure, you add more powder. Want the pressure sooner, make the granules smaller. Longer pressure in the barrel for more velocity? Make the granules larger. If you make them too big, they just get blown out the end of the barrel before they are consumed. That is loud crack, fire and slower bullet speed.

HTH

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BudHyett posted this 11 April 2019

Black powder is an explosive, smokeless powder is a propellant. The actuality is much more complicated than this simple expression.  The chemical composition and physical characteristics of the kernels for both determine burning rate and influence the results.

IMR powders have the same chemical makeup, burning rate is determined by physical shape. The faster powders are smaller kernels with holes through the kernel to allow burning from outside in and inside out. They are consumed more quickly. Slower powders have longer kennels with smaller holes to retard the burning. They are consumed more slowly. 

Black powder burning rate is not that simple. The size of the kernel does determine burning characteristics. It takes longer to consume bigger kernels, thus there is an observed slower burning rate. FFFg in a pistol barrel because you want energy quickly and not much space to burn it in. 1 1/2 Fg for target rifles because there is more space for burning. Black powder manufacturers use different proportions and mix the ingredients differently.

Thinking one's way through the ignition of black powder in a cartridge, there is a sequence of steps happening in milliseconds. The primer ignites as an explosive and the initial ignition of the black powder is an explosive. This creates both pressure waves and flame. The pressure waves progress through the powder mass and are absorbed by the base of the bullet, Pressure and temperature being intro-convertible, the base of the bullet begins to soften and expand. Simultaneously, the flame begins the powder burn that expands the powder column and pushes against the bullet base further expanding the base and beginning the bullet's travel. Now you have a semi-fluid mass filling the rifling bore and moving down the barrel. The powder continues to burn as long as the flame and pressure sustain ignition. 

Thinking ones way through the ignition of a smokeless powder cartridge, there is one difference. The primer ignites and the smokeless powder begins to burn and does not contribute as much to the pressure wave. When any fire starts, there is a pressure wave. The faster and stronger the ignition, the larger the pressure wave. Smokeless powder burns in a controlled fashion, shape and retardant coatings controlling the burn rate. Bullseye and similar powders will do much better. 

Based on the above, I know more than I understand. I shoot Accurate Arms #9 and 4100 powder, they are not as fast as Bullseye. However, they are more consistent. 

On a side note; I remember an article in the California Rifle and Pistol Association magazine where a shooter made his own black powder. He made three varieties, one with commercial briquette charcoal, one with hardwood charcoal and one with softwood charcoal. The softwood charcoal gave the least fouling and the highest, most consistent velocity. 

Country boy from Illinois, living in the Magical Pacific Northwest

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Squid Boy posted this 11 April 2019

BP was hard to get as a kid but potassium nitrate was easy so I made my own using sugar, sulfur and potassium nitrate. All melted together in an iron skillet over a low fire. Yes, I was the poster child for disaster but never had a flame up. When the stuff cooled it was hard as rock and I broke it up with a hammer and the put it in a pie tin with a couple steel balls out of a pinball machine. About an hour of shaking would grind it down pretty fine. Made great fuel for rocket motors and worked OK in shotgun shells but it liked water and you had to clean the guns pretty quick. The burning rate was fast. It was lots of fun. Just thought I would throw this in. Squid

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Wineman posted this 12 April 2019

Homer Hickam's book "October Sky" is full of references to the sugar, sulfur and other mixtures to launch his rockets. Even today there are plenty of recipes for this type of fuel. As a kid we would take empty pellet gun CO2 cartridges and drill out the foil. We would fill them with book match heads (the kind every restaurant would give you at the cash register), put in a piece of Jetex fuse and have an improvised rocket launcher with a piece of 1" pipe. Once I thought one might have detonated rather than fly. Fast forward 50 years and I'm working with a guy with a hand missing. After we get to know each other I ask him what happened. Same drill but he was using "Strike-Anywhere" matches and eventually stuffing them in caused an ignition and explosion in his house, taking his left hand completely off. Talking to this guy was like watching myself from another body. Same Sh*% different guy. Why I still have two hands and he doesn't is a mystery to me.

Dave

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Ross Smith posted this 12 April 2019

Bud gave a very good explanation. Black powder is an explosive. Smokeless has a progressive burn. Make a trail of black powder and one of smokeless 10 feet long and ignite them one at a time. The smokeless will burn slowly from one end to the other. The black will ignite all at once. They each have their own rules of usage and they are much different. There is a youtube video of a guy doing experiments and comparisons of black and smokeless. good luck and be safe.

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Squid Boy posted this 12 April 2019

Wineman, we are getting a little off topic but your mention of Jetex fuse really brought back memory's. Great stuff and yes it is a wonder I have all my digits especially when I started using powdered magnesium and sulfur. Anyway, black powder is highly degressive and the rate that gas is evolved is greatly reduced as the grain burns due to a reduction in surface area. I read a study that put the burning rate within a grain at .2 ft/sec but the propagation rate from grain to grain at 30 ft/sec. I don't think this helps the discussion much but as a low explosive I believe the cut off point is sub-sonic as far as burning rate is concerned. Everything above is high explosive. Thanks, Squid Boy

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Ken Campbell Iowa posted this 12 April 2019

... when my brain reached about 50 % formed, i found that i could cut the end off an extension cord, then form fine armature or magnet wire into a coil and connect it between the two extension cord bare ends.   plugging the cord into an outlet made a great spark of the coiled fine wire.  and the longer the extension cord, the braver i got with what i set off with the greatest toy ever for a bored farm boy.

***********

i really didn't need my basic training ... i already knew to duck when i heard a loud noise ...

*****************

when a few years ago remington offered their electric ignition rifle, i laughed .  been there ...

ken

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