Measuring powders.

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Cowled_Wolfe

New member
Hello there. I've got a question which has been getting at me for what seems like ages...

With black powder, you measure by volume. With black powder substitutes, you measure by volume. With smokeless, you measure by weight... Why?

I've got two theories on the issue, but I don't have any certain knowledge:

1. Black powder and substitutes run at much lower pressures, so you can approximate the same weight each time if you go by volume -- in a smokeless rifle, an accidental extra grain or two might blow the rifle up.

2. Black powder and substitutes have some wierd physical property where one volume of powder will have the power of the same volume, even if they don't weight the same... One volume of smokeless will have the same power as another volume of powder only if they weight the same...

For some reason, the second theory seems wrong to me... But the first theory seems plausible... So what's the deal? Why is it volume for BP/substitutes and why is it weight for smokeless?

TIA for any info,
One very confused Wolfe...
 
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Rodger Peterson

New member
I have no idea, but here is a guess. Because of the way different smokeless powders are cut (ball, cyclinder, ect.) The same wieght may take up more or less space in the case. Black powder generally is called to fill the case completely no matter of uniformity.
 
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Mike Irwin

Staff
Black powder and most of the substitutes burn at a constant rate. Compressed tightly, or sitting loose in a pile, they burn at the same rate.

Smokeless powders don't do that. They're progressive burning. Lay a small pile on the ground, and it burns with a weak orange flame and is very sooty. Put it under pressure, and it burns a lot cleaner, and with a lot more force. The more pressure, the more efficiently it burns, which in turn creates more pressure, so it burns even more efficiently, so it generates even MORE pressure, and so forth and so on.

Black powder has one basic chemical composition, too. There are variations, but you need three standard ingredients -- charcoal, sulphur, and a nitrate. If you alter the composition too much, you get a propellant that simply won't propel anything.

Smokeless powders, on the other hand, have what really amounts to an infinite number of mixing permutations.
 
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d_mikey

New member
Another issue is that black powder and pyrodex are both very hydroscopic- they attract water from air. Weight may vary with humidity.
This is one of the advantages of smokeless over blackpowder. Blackpowder residue left in a gun will attract moisture and promote corrosion.

Mikey
 
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Smokey Joe

New member
Measuring black and smokeless powder

Here's another take on the subject:

The blackpowder substitutes are MADE to shoot volume-for-volume like original black powder. They are not made the same weight-for-volume as blackpowder. So if measured weight-for-weight with blackpowder the charge of a substitute would be off, possibly dangerously so.

Why are blackpowder and its substitutes measured by volume in the first place? My theory is that it is easier in the field to measure volume consistently when you're loading a muzzleloader after having fired at a deer. A volume-adjustable measurer is not nearly as fussy as getting out a set of scales.

When cartridge firearms were invented, their blackpowder charges began to be measured by weight, hence the names of some of the older cartridges, e. g. .45-70 (.45 caliber, 70 gr. of blackpowder,) .45-90 (same caliber but a larger case with 90 grains of blackpowder) .30-40 Krag, and so on.

When smokeless powder came on the scene, it was always used in cartridge arms, so it was measured by weight as well—although the charges were much different: a .45-70 cartridge with smokeless will definitely NOT have 70 gr. of powder.

As has been pointed out, smokeless powder is made a variety of ways. The different powders are NOT made to be measured volume-for-volume. It is nearly always loaded under controlled conditions, like a reloading bench, where a scale is readily to hand and a wounded deer, or other similar exciting emergency, is not present. When it is loaded by volume (as from a powder measure, or a charge bar in a shotshell reloader,) this volume is checked constantly by weighing the charge.
 
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Mike Irwin

Staff
Measuring by volume...

Unless you weigh EVERY charge, we all measure our powder by volume in some way or another.

Every mechanical powder measure, Lee dippers, etc., measure powder by volume. We simply select the right "hole" that will give us approximately the amount of powder (in grains) that we want.
 
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d_mikey

New member
I did a little further research on this topic as I found it interesting. One point that did come up was that black powder burns at very different rates depending on grain size and structure. Very small particles start much more easily and burn much faster. Larger grains are harder to get ignited, and burn slower. Think of it as the difference between twigs and logs.
There apparently are often warnings on black powder containers that warn not to shake the stuff. Breaking the grains to smaller size can lead to more dense, faster burning and more powerful charges So when measuring by volume, be sure you are using powder in good condition, and the exact type given in the formula.
 
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Mike Irwin

Staff
"One point that did come up was that black powder burns at very different rates depending on grain size and structure."

Yep, I should have explained that concept a bit more thoroughly.

However, even though the burn rate is different based on the size and shape of the grains, the absolute burning rate remains constant no matter how much pressure you put it under.

Oh, and technically black powder doesn't burn. It's a low explosive...
 
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