Explosive power by weight or volume?

[El Chivo]

I know most reloaders measure by volume for everyday stuff, and when it's critical, by weight.

I heard a story about a guy who lives in the desert. He weighs out his rounds. When he noticed extra-hot loads, he sent the powder to the manufacturer for a look. They were amazed at how far off it was, and wouldn't tell him any more about it. He surmised that the powder lost moisture and so weighed less than it should have.

My question is, would the explosive power of the charge have stayed the same if measured by volume? Or would the granules have shrunk with the moisture loss?

(assume perfectly consistent measurement by volume)

[Tycer]

An uneducamated guess is that powders with a cellulose base will swell and those with a petroleum base do not.

I do not know which powders are which, but would also guess that newer powders are not cellulose.

And I can't wait to see how way wrong I am!

[J Miller]

Although I use my powder measure to throw charges I always verify their weights with my scale. I never just assume the powder measure setting is on for any powder.

I've also never had powder change is burning rate to such an extent. I never leave my powder cans open either. I open them, pour the powder into my powder measure and trickler then close the can. After loading I put the remainder back in the can and close it tight.

From my experiences if a powder changes significantly the loader must be leaving the can open when it should be closed.

Joe

[Boreman]

+1,what J Miller said. Be safe!!!!!

[Griff]

Except for the original gunpowder, ALWAYS weigh charges before loading ammo. Don't get me wrong, I use a volumetric measure, but only after verifying that the volume I'm using weighs correctly for the charge I want. While the Lee measures are also a volumetric measure, they've been calibrated for a specific powder.

Remember, these are "controlled bombs" we're making... it ain't rocket science, but... miscalculations can cause a big boooom!

[piller]

Power is mostly a function of how much volume of byproduct the material produces when the chemical bonds release. The speed with which they release gives the shattering effect, or brisance, and that is part of why faster burn rate powders are used in smaller volumes. The brisance of TNT is 1, and that is the base of the calculations used to destroy things. 2 units of nitroglycerine produce 7 units of byproducts. The swelling of the product of hygroscopic change, or shrinking if that is what happened, should have not affected things to the point of the factory going to Pucker Factor 10. Something was wrong with a mis-labeled product, or at least I presume.

[flatnose]

I have experienced large variations in powder densities in similar powder from different kegs. Even to the point of wondering if the keg had been mis labeled.
This happend only once, and I had to work up my loads again. I managed to reach the previous grain weight for the charge with no ill effects.

[gimdandy]

I believe that your answer lies in your description of his residence "desert". If you look in your reloading manual (hodgdon in this case ) and in the front it explains their "EXTREME" line of powders'. Page 45 in #13 SPEER talks about possibility of a load developed at 40 degrees and then fired at 100 degrees may have excessive pressure, this is under paragraph titled "Pressure Variations With Temperature " . Finally , since he lived in the desert I bet you he stored his powder in the hot desert !!!! Heat will destroy the integrity of gun powder .
It's very interesting about the old cordite ammunition that they used to use in Africa , and it was for these very same reasons

[El Chivo]

I have experienced variations due to temperature, but not in the powder itself. I'm switching to Hojjjduhn Extreme Powders for this very reason.

What I was wondering, if he had measured his degraded powder by volume rather than weight, would explosive power stayed consistent (even though the weight would have been less)?? Or would moisture leaving the powder make it shrink and make volume measurements untrue as well?

This guy is a good gunsmith, and has lots of stories that make you think. For example he was talking about WWII Japanese ammo. The powder they used would degrade after a few months and turn into nitroglycerine, so people picking up rounds of ammo after the war could have them explode in their hands quite readily.