Powder grain size effects on velocity

[Newtire]

Black powder burns from the outside to the inside. Smaller grain sizes burn faster than larger grain sizes. But while smaller grain sizes can give an initial higher pressure it all depends on the barrel caliber and barrel length. A larger caliber rifle typically does better with larger grains which give a slightly longer burn time to achieve best velocity. A pistol or revolver can benefit from smaller grain powder. But, depending on the gun, all the granulations will work. Certain guns will prefer exceptions to the rule.

This is something I had never thought of before. Makes real good sense to me.

 

[chorizo]

This is something I had never thought of before. Makes real good sense to me.

Based upon my reading carbines do better with the faster burning powders as the pressure peak is sooner and it allows for a more complete powder burn in the shorter barrel.

I am about to find out in my carbines if the weather/temp ever gets above arctic level.

 

[Some_Mook]

I don't believe 4f is going to blow your gun up though. Black powder only generates so much pressure.

Where people can run into trouble is when the pressure develops too fast in too short of a time-frame.

It takes time to bump up a projectile and get it moving from it's at-rest position. If the charge is releasing energy faster in that time frame because the charge is being fully consumed in less time, as it would be in a smaller versus larger grain size, the pressure is developed faster. The powder doesn't 'burn faster' but the powder's total time for complete conflagration is shorter and the development of peak pressure is faster.

Black powder of a given composition of materials and density, by mass, only contains a certain amount of potential energy.

Black powder is classified as a low explosive, but it is still an explosive material.

A high explosive would be categorized as such because it chemically converts all of it's stored potential heat energy instantaneously when detonated.

Black powder grain size regulates the speed at which it's potential energy is released. The total amount of potential energy available is regulated by the chemical composition of the powder and the density of manufacturing. Different wood = different charcoal = different energetics of composition. Greater density = greater potential energy in a smaller volume of space.

Smaller grain size develops it's peak pressure sooner because all of the potential energy is released sooner because the smaller grains are fully consumed sooner.

A faster rise in peak pressure is a more violent event.

By way of analogy, in a gasoline combustion engine if the fuel and air charge combusts too fast, the result is described as detonation (it explodes). Detonation blows holes in pistons. A lean air/fuel charge (less gasoline) burns hotter in a shorter period of time than a rich charge (more gasoline) and the faster build-up of heat and pressure from the hotter lean charge can cause the gasoline that has not yet burned to spontaneously combust all at once instead of linearly.

This sudden release of energy is very violent, and can cause damage even though the total amount of potential energy in a rich charge is greater than that of a lean charge it is the rapidity of the development of peak pressures that do the harm.

 

[chorizo]

Where people can run into trouble is when the pressure develops too fast in too short of a time-frame.

It takes time to bump up a projectile and get it moving from it's at-rest position. If the charge is releasing energy faster in that time frame because the charge is being fully consumed in less time, as it would be in a smaller versus larger grain size, the pressure is developed faster. The powder doesn't 'burn faster' but the powder's total time for complete conflagration is shorter and the development of peak pressure is faster.

Black powder of a given composition of materials and density, by mass, only contains a certain amount of potential energy.

Black powder is classified as a low explosive, but it is still an explosive material.

A high explosive would be categorized as such because it chemically converts all of it's stored potential heat energy instantaneously when detonated.

Black powder grain size regulates the speed at which it's potential energy is released. The total amount of potential energy available is regulated by the chemical composition of the powder and the density of manufacturing. Different wood = different charcoal = different energetics of composition. Greater density = greater potential energy in a smaller volume of space.

Smaller grain size develops it's peak pressure sooner because all of the potential energy is released sooner because the smaller grains are fully consumed sooner.

A faster rise in peak pressure is a more violent event.

By way of analogy, in a gasoline combustion engine if the fuel and air charge combusts too fast, the result is described as detonation (it explodes). Detonation blows holes in pistons. A lean air/fuel charge (less gasoline) burns hotter in a shorter period of time than a rich charge (more gasoline) and the faster build-up of heat and pressure from the hotter lean charge can cause the gasoline that has not yet burned to spontaneously combust all at once instead of linearly.

This sudden release of energy is very violent, and can cause damage even though the total amount of potential energy in a rich charge is greater than that of a lean charge it is the rapidity of the development of peak pressures that do the harm.

A great explanation of why prudence is the watchword in experimenting with loads out of the norm.

 

[Nuthatch]

i tried my homebrew for this. what i found was ffff produced a more noticeable "crack" when loaded with just thumb pressure on the rod.
accuracy was dismal in the .54. ff and fff gave good results.
what did amuse me was if i thumped the ball/patch with the rod until the rod bounced i had a heck of a time igniting the charge. my story is it compressed the ffff into a pellet without the angular grain to catch fire. I had to pick the vent repeatedly to make it work.

I've noticed that the raw meal powder is MUCH slower to burn, presumably because there just isn't any space for the flame to move through the powder. After granulating, it's incredibly fast.

I figure this might be why I've had some issues with accuracy with it (pretty sure it cost me a turkey last season). Since I don't compress my powder or use a binder, simply crushing with a range rod during loading can change the granulation. As I have gotten more consistent in my loading procedures, my accuracy with it has improved.

 

[smoothshooter]

When I shoot 30gr of Goex VS 30gr of 777 there is a big difference.
So as I figure out how to keep the smoke from covering the gates Im gonna chrony the 44 again.

Is 777 hotter?

 

[chorizo]

Is 777 hotter?

Yes, 10 to 15% more vigorous is what has been observed

 

[Britsmoothy]

Some of the fear mongers on here have me wetting my pants....with laughter!

The above is a mix of 4&3f and it goes in my 10g with up to 2oz in front of o so desire!

So what they are sayin, the fear mongers, is that if I get a load of coal slack and throw it in my stove I'm gonna melt the stove! No, it doesn't.
The slack behaves like a solid lump and actually burns slower! Also just as my stoves have a vent so do muzzloaders.
So fear ye not fear mongers, especially in the light of the fact ye canny not produce one single account of failure of a piece from using 4f in anything!
Utter nonsense....

 

[Tenring]

Black powder in a solid form burners more like a fuse, It needs air space around the kernels to generate pressure therefore faster ignition and greater the speed. In any form it’s not going to blow up any guns but to use 4F definitely would not be my choice unless it was absolutely my last resort and all I had. 4F is for priming, Silly Rabbit Trix Are For Kids, LOL A little Levity to go along with it..

 

[Britsmoothy]

4F is for priming,

No it's not but it can be used for priming, just the same as 3,2&1,f can be.

I have not seen one can of 4f with any warnings on how it should not be used. Have you?

 

[nkbj]

No problem with adjusting my charges through load development. The lesser density in settled charges, burning characteristics and fouling were different but it went boom and the intended point of impact got perforated. Not the type of powder to use in revolvers if you're after more velocity due to their fixed volume in the chambers.

 

[Tenring]

i Have used 2F And 3F for priming without issue, I should have said Preferred most suitable size would be 4F. Everybody Happy Now…

 

[Patrick Shaw]

I'm bent on trying to improve the round ball MV of my Pietta 3" barreled 1860s over the 525 fps that The Duelist recorded using 3F. The measured-by-weight charges of 4F listed in the First Edition Lyman BP Manual with their actual Lead Units Of Pressure measurements plus Chrono Data gives me hope of doing exactly that some day.
Another avenue I intend to (UBER-CAREFULLY!!!) explore is the possibility of reducing tiny quantities of Sheutzen 4F ground to "Dust" or 5F and segregating it from the main charge with nitrated paper to prevent mixing. Thinking now I might clamp some leather over the flash hole to prevent the 5F from slithering out, put tiny quantities of Dust in first, a paper membrane - and then the main charge under a ball rammed to the prescribed fifty pounds of force used by Lyman.
I have read of historically preserved paper .44 CB "cartridges" being dissected and analyzed as containing 17gr-by-weight of 5F. Those also were safely used in the 8" barreled 1860s of their day. In fact before the modern Cowboy Action Black Powder Pistol craze began using a mixture of 2F&3F in their BRASS cartridges - 5F Dust was indeed sold as "CTG" (cartridge) powder by the barrel (only) to manufacturers of .44 paper cartridges. Practically speaking it could not be loaded as loose powder 1) Because it would slither out the flash hole and 2) because of the small quantities involved and the imprecision built into volume loading of "Dust" (the stuff is like flour - it goes through a #100 screen after all!) - it just "wasn't done" (people had Common Sense back then - no need for legislation and regulation of every-dang-thing)
Please give me your well-considered opinions on this. I can't say I know all about it already

- but I have a pretty good picture of what NOT to do when experimenting with internal combustion devices.