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Old March 11, 2012, 01:46 PM   #1
varmiter
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BP Load Compression

Has anyone done any experimentation on how accuracy, velocity are effected, or if they are effected by the compressing of say 3Fg powder.

My theory, and it’s only a theory mind you, is that the harder a powder is compressed, the slower the burn rate. Two granules of powder, sitting next to one another when the fire travels it will find a path between the two granules and they will burn quickly. However if those two granules are pressed hard together, the fire cannot find a pathway between them and thus travels around them actually slowing the burn rate.

Does this make sense or am I all wet?

Chris
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Old March 11, 2012, 01:58 PM   #2
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See my response on The High Road. Better yet, here it is:

If you can explain the physics of:
Quote:
if those two granules are pressed hard together, the fire cannot find a pathway between them
then perhaps I'd say no, you're not all wet. But it seems to me that heat (which is what causes the individual granules to burn) will easily be more easily transferred between two granules that are pressed hard together.

The heat of the gas from the percussion cap is what initially ignites some of the powder granules; heat, and hot gas, from those burning granules ignites the adjacent granules, etc.
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Old March 11, 2012, 03:56 PM   #3
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This is an interesting discussion...not everybody is fascinated by the science behind their favorite pastime, but to me it is one more thing that makes it enjoyable. That said, I'm no intellectual on these things (but do like to sit in on the conversation to see if I can learn something).

Keep goin"!
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Old March 11, 2012, 04:49 PM   #4
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A little background. I’m in the process of setting up to make my own BP. Which is CONSIDERABLY different to the commercial BP substitute.

Apparently, the substitute(s), actually perform more consistently when only lightly compressed. The reasoning is the binding agent on the granules used to help control the burn rate are broken down under high compression. Since real BP does not have such an agent, unless you add it yourself, it is a much hotter load by weight.

I’m a lazy sod and like to use my spare time doing something that will make my range time much more fun, and or interesting. My BP out of the ball mill has the consistency of talcum powder. This airfloat is then compressed under almost two tons of pressure into a puck/plug, from here I can granulate it down the ‘f’ size I want. Anything finer than that goes back into the press for recycle, so nothing is wasted.

Once again, REAL BP.....I would like to create a plug that fits the chambers in my BP revolvers. I can make a bunch up and take them to the range. Makes reloading much easier, and faster. I just don’t know how well it will work, or even if it will work at all. One thing tho, real BP is much hotter than the substitutes, so it will be like starting up a load for a particular cartridge in smokeless. Start low and work up.

Oh.....instead of the $20.00/lb for the substitutes, I have the cost down to $1.78/lb. Now you know why I'm so interested in making this work.

Chris
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Old March 11, 2012, 05:34 PM   #5
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Quote:
Apparently, the substitute(s), actually perform more consistently when only lightly compressed. The reasoning is the binding agent on the granules used to help control the burn rate are broken down under high compression. Since real BP does not have such an agent, unless you add it yourself, it is a much hotter load by weight.
777 is the only one I'm aware of that needs light compression. I know you can squash the heck out of Pyrodex and it has no effect.
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Old March 11, 2012, 06:21 PM   #6
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Quote:
Since real BP does not have such an agent, unless you add it yourself, it is a much hotter load by weight.


Real bp is 'hotter' by weight than 777?

I don't think so.

777 must be reduced by 15% by volume to get a charge equivalent to a given weight of real black powder. That's REDUCED by 15%. Thus 100 gr/volume of real black powder will give the same muzzle velocity and energy as 85 gr/volume of 777....

777 is less dense than real black powder, so that a given volume of 777 will weigh significantly less than the same volume of real black powder; in fact, 100 grains by volume of 777 weighs 77.7 grains, while 100 grains of real black weighs 102 grains.

So, if I load equal weights of 777 and black powder (say 100 grains), the 777 charge will be 15% (at least) MORE POWERFUL than the real black powder charge.
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Old March 11, 2012, 08:06 PM   #7
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OOOOKKKKK

While that may be true, the approximate 33% higher price makes it a complete non starter for me.
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Old March 11, 2012, 08:59 PM   #8
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You can choose to use or not use 777 for any reason you wish; I don't use it myself. I just thought it was important to set the record straight on the relative power. Where did you get the idea that black powder was so much hotter?
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Old March 11, 2012, 10:51 PM   #9
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Pyrodex is a straight across sub for real bp by volume but go by weight and Pyro will blow your socks off.
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Old March 12, 2012, 03:52 PM   #10
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I ran a little experiment to see just how light a load I could shoot in my 1860 Armys. I used no wad and I started getting delayed ignition of KIK FFg at around 18 grs. You could hear the cap fire then the main charge. If I added a 1/8" lubed felt wad the charge would go instantly as you would expect. The only variable I could see was the amount of compression I put on the powder.
I went back to 25 grs/weight or 29+ grs volume (not quite 30 in my measure).
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Old March 16, 2012, 12:34 PM   #11
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I know at least some modern powders rely on rapid pressure inside the case to increase burn rate. A British 303 with strings of cordite has space in the case.
Heard a story don't know if it really happened.
Soldier captured on exercise refuses to divulge info. He had a thick piece of cordite wrapped round his thigh and a fuse attached. When threatened with lighting the fuse he sang like a bird. Cordite I believe will burn like a firelighter in the open air. Would you risk it.
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Old March 16, 2012, 10:34 PM   #12
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Cordite, smokeless, or nitro powders all burn slowly in open air if lit with a match.
So will most high explosives, as the "underwear bomber" learned the hard way.
or so I have heard
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Old March 25, 2012, 11:46 AM   #13
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Read Hatchers notebook

It has a picture of a truck flattened by an explosion. CAUSE. The military burn explosives(cordite?) or used to then in open air bonfires. This particular bonfire was made to large, the pressure of the unburned explosive accelerated the burning process causing an explosion which killed the occupants of the truck which was quite a distance away.
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Old March 25, 2012, 12:45 PM   #14
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I have not, but I remember years ago reading an article by someone who used some device that could measure the psi of the compression force, and if I recall correctly, unless one compressed the powder charge so heavily that it shattered the individual grains, the more compressed the charge, the higher velocity was obtained, along with a much lower standard deviation.

Many high explosives burn slowly, but when set off by a detonator, they detonate, well, explosively! That is why smokeless propellant is not an explosive, but blackpowder is (albeit not a high explosive).
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Old March 25, 2012, 06:30 PM   #15
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I sell substitute bp. most customers now want and demand trip7. i didn't like it. i still use pyrodex. jim shockey/trip 7 has (or probably has) lubricants that make it clump if moist. pyro has graphite in it but it is the best i know of when substituting real bp. But dang it----most customers want trip 7. So there must be a reason
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Old March 26, 2012, 02:49 PM   #16
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There is- they haven't tried BH209!

27 shots without swabbing the bore and #27 loaded as easy as #1.
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Old March 26, 2012, 03:28 PM   #17
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I do not claim to be an expert.For BPCR,I made a brass depth gage for my powder level in the case,so I can set up for about 1/16 in compression.

I have an old Ned Roberts book(reprint,not original) "The Single Shot Cartridge Rifle" or close to that.I found a very interesting tidbit that I have not tried yet.He includes the recipes some of these old timers used loading cartridges.

Intuitively,I might think that if I were to put in a small amount of priming powder over the primer(I do not) I might use a fine granulation.

These guys would put 5 or 10 grains of fg.Coarse powder,over the primer.I can see some advantages.Less likely to foul the flash hole,more porous,to allow the primer flame to filter through and disperse,and a touch softer start,so perhaps less likely to slump the ogive on softer alloy bullets.

It may be something to work with.
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Old March 27, 2012, 07:13 AM   #18
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Bp

Black powder - a low explosive - burns pretty much at the same rate whether it is confined/compressed in a cartridge as it does in the open air. Smokeless propellents are progressive burners...the higher the pressure, the faster the burn.

I have always wondered:
Quote:
27 shots without swabbing the bore and #27 loaded as easy as #1.
Why is that quality important? It is an oft cited quality of various powders and guns. As a shooter who swabs after every shot, I don't understand why being able to shoot 5-10-20-27 in a row is important. Nothing wrong with the idea, of course, but so what.
Jus' askin'.

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Old March 27, 2012, 07:58 AM   #19
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BP burn

All BP burns from the outside in and unlike smokeless powder it's all the same. By that I mean that in the making of BP, the three chemicals are mixed together with water and it's compressed into a large look like hockey puck.
Some powder makers use what is called a ball mill to break it down into the needed grain size. Goex uses the wheel mill.
Your Fg powder and 3 F powder are the same with the only difference being the grain size and how long it's refined.
If a company leaves it various grain sizes in one batch then that powder will burn slower than one that has all of the grains about the same size and smooth outer surface. This will make for a faster burn.
Take a slide of 3 f and 2f and look at them under a microscope. You will understand right away why the 3f produces higher velocity.
Look at Swiss powder and then Goex and you will see why the Swiss is a better and more consistent powder.
In BPCR shooting you will have some bullets that are seated on a compressed charge of .385 and above. These rounds are very accurate.
The top shooters are even placing newspaper or tissue across the primer flash hole to even out the flash and receive a better burn for it.
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Old March 27, 2012, 08:09 AM   #20
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The original question has been lost in a lot of verbiage about subsitutes.
IMHO, compressing will change bp performance. How and by how much, I don't know. However, I am sure there is no advantage to doing so. The top precision shooters (bench, slug and long range) are more concerned with consistency of compression round to round than how much. And their 'compression' is really not much, just a firm seating of the ball. I see no point in fretting over or messing with this notion. Load, be consistent and enjoy.
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Old March 27, 2012, 03:31 PM   #21
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Quote:
There is- they haven't tried BH209!

27 shots without swabbing the bore and #27 loaded as easy as #1.
I can beat that with my 58 Enfield and Pyrodex. Besides why should I pay three times as much for less powder that takes a 209 primer to set off?
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Old March 27, 2012, 04:42 PM   #22
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compression

slight clarification:
Quote:
in the making of BP, the three chemicals are mixed together with water and it's compressed into a large look like hockey puck.
Some powder makers use what is called a ball mill to break it down into the needed grain size. Goex uses the wheel mill.
There's more to it than mixing with water and forming a puck. The water is present so as to insure that the mix will not ignite as it is being worked by the mill. Simple mixing results in "green powder" aka polverone. To be true black powder the ingredients must be incorporated - combined so that they cannot be separated.
The ball mill (wheel mill?) is used to incorporate the three chemicals. The process takes hours. After they are incorporated and while still damp the mix is pressed into a cake and then forced through a screen - actually a series of screens, iirc. It is the screening that determines grain size. Then it is glazed.
It is always possible that the large scale manufacturers use other methods - alcohol precipitation is one - but the method described is the classic means.
Does Goex use the alcohol method? It is much more risky than the mill.
There is continuing discussion on various fora about whether compression is needed at all. I thumb press my Postells into unsized cases...contact with the powder - yes. Compression? Not much, if any.

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Old March 28, 2012, 02:16 PM   #23
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Quote:
Why is that quality important? It is an oft cited quality of various powders and guns. As a shooter who swabs after every shot, I don't understand why being able to shoot 5-10-20-27 in a row is important. Nothing wrong with the idea, of course, but so what.
Jus' askin'.
Well, I'd say that when shooting some sabotted bullets, after shot #1 they can be a PITA to load. At the bench, no problem. In the field, if your first shot is off, and shot #2 is loaded and fired without effect, shot #3 may be a long time coming. Had it happen once. Not a pretty picture.

So, in that light, it is nice to know that a quick follow-up shot, or a third, can be just that- quick.
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