Letting Powder Breathe ??

[Berger.Fan222]

Seldom have I read so many opinions that were arrived at without any investigation at all. In the August 2011 issue of Precision Shooting, an article titled "The Effects of Humidity on Velocity chapter 2" written by Alan Peterson, describes well done testing that firmly establishes the relationship between powder moisture content, and velocity. The test was very well done and documented. Drying and humidifying the same charges of 26 grains of H322 in a 6PPC caused a velocity difference of over 300 fps. The powders used in the test (with different calibers) were H322, N-133, H335, and H4831SC. The latter showed a range of moisture content from 0 to 1.9% and corresponding velocities of 2,895, and 2,570 for a 56 grain charge in a .270 Winchester. Just because this sort of information has not bee widely published says nothing about its validity. In every case, the dry powder produced the highest velocities. I have scans of the pages of the article. One of the most successful benchrest shooters of all time conditions his powder to arrive at a specific moisture content, and he is not alone in this practice.

As I recall, Don Miller's article pointed to two main theoretical causes of these effects:

1. When powder contains more moisture, a given weight of powder contains less nitrocellulose, because some of the weight is water. For example, at 2% water content, 60 grains of powder contains 1.2 grains of water and only 58.8 grains of dry powder. At 0% water content, 60 grains of powder contains 60 grains of dry powder.

2. When the powder contains a higher water content, energy is expended by the burning powder vaporizing the water rather than accelerating the bullet (or raising the pressure). Water has a very high heat of vaporization, so removing all the water from a quantity of powder leaves a lot more energy to raise the pressures.

It's not a matter of powder exposed to different humidity levels failing to ignite or creating dangerously high pressures (unless a hot load was already borderline). It's more a matter of powder with different humidity levels varying in muzzle velocity in ways that may well impact long range accuracy.

 

[fguffey]

"Keep your powder dry"

A reloader could purchase a vacuum pump and vacuum can and gages. After the purchases the reloader could weigh the powder then place the powder into the vacuum tank then place a vacuum on the container. After about an hour the reloader could weight the powder again.



F. Guffey

 

[BoydAllen]

The procedure was to first load cases with powder from a freshly opened can, and then do all the other processing to change the moisture with the powder in the open cases. This meant that the actual number of granules in each case remained constant. It was a clever piece of work. The method used was one that anyone could duplicate.

If you think about it for a minute, if a short range benchrest shooter is loading at the range with his powder in a measure that does not protect it from exposure to ambient humidity, and that humidity would tend to dry the powder throughout the day, that would increase the powder's effective speed, AND if the ambient temp was increasing throughout the day that would also cause an increase in pressure and velocity, (even with preloaded ammo). So, we have two factors at work that can both increase pressure and velocity. Some powders are less affected by these factors. That is why so many top shooters shot T powder (one lot of surplus 8208) until their supplies were exhausted, and that was the driving force that eventually resulted in the production of LT 32 and LT 30 (thanks to Lou Murdica, and Western Powders).

 

[Dusty Stevens]

We need a powder that adsorbs less humidity. Maybe a coating

 

[Alex Wheeler]

If you dont see a difference letting your powder breathe or letting your cases rest after sizing maybe your not paying attention. Its wise to form opinions from experience.

 

[Taildrag15X]

"Keep your powder dry"

A reloader could purchase a vacuum pump and vacuum can and gages. After the purchases the reloader could weigh the powder then place the powder into the vacuum tank then place a vacuum on the container. After about an hour the reloader could weight the powder again.



F. Guffey

Already have a vacuum pump and chamber but don't think I'll be opening any powder around them......

I keep the lids on unless I loading, then it's opened, poured in the measure, dumped in a case, sealed with a bullet usually with in minutes in the controlled environment of my basement.

 

[jlow]

I guess the question is what exactly is the effect of humidity. If it’s effect is being absorbed into the powder causing greater weight for the same volume which would mean the same wet powder weight would have less propellant, which BTW would explain why dry powder to have more velocity since there would be more powder for the same charge weight.

So going back to the OP’s question and from this standpoint, since the OP weight the powder first and already have them in the case, even if it absorbed water, it should perform like the same weight of dry powder weight today. It would be an easy test for the OP.

 

[BoydAllen]

I suggest that you read the article. The author's results for H322 in a PPC were that freshly opened powder (25 gr. charge wt.) contained .9% moisture. The powder that that was dried in the cases became .9% lighter. The powder that was humidified at 66 degrees came up to a moisture content of 1.8%. Humidification at a higher temperature (102 degrees) increased moisture content to 2%. Drying the powder increased the average velocity (compared to loads using freshly opened powder) from 2,892 fps to 3050 fps., a change of 158 fps. which is a little over 5%. The powder that was humidified at 66 degrees lost 159 fps (compared to loads using freshly opened powder). The powder that was humidified a the higher temperature, to 2% moisture lost 195 fps. Taking the extremes from fully dried to humidified at 102 degrees, the difference in average velocities was 353 fps. Just sitting around open in his basement lowered the out of container moisture content from .9% to .5% for a change in velocity of 98 fps. From these results it can be see that changes in the velocities do not track with simple changes in the weights of charges. Consulting 6PPC data in my Berger manual, for 68 grain bullets, the average computed increase of velocity per grain of 322 works out to be 111 fps. The maximum difference of charge weights for this powder in the test for this cartridge and powder was 2% which was roughly a weight difference (starting with a 25 grain charge) of approximately half of a grain. If changes in observed velocity were only based on differences in charge weight the they would have been about 55 fps at the extreme. This is the reason that this article is so important. Comparing dry powder to the most humidified, a weight change due to moisture, of 2% produced a velocity difference of 13%.

For the curious, the testing done with 133 with a out of the can charge weight of 28 grains showed a moisture content of 1.1%, which dried to .5% just sitting in open cases in the authors basement. This resulted in a a velocity increase of 87 fps from that .6% moisture change. Looking at the extremes, a 1.8% difference from dry to wet (@66 degrees) the difference in average velocities was 233 fps. The humidification at a higher temperature was not done with this powder.

 

[fguffey]

"Keep your powder dry"

First check the humidity level, then develop the load. later when using the same powder with the same load check the humidity level. If the humidity level is low add water. If the humidity level is high place the powder in a vacuum, or add desiccant bags.

I suggest cutting down on the time the lid is off the jug and I suggest using small jugs to cut down on the time the powder is exposed to the atmosphere.

F. Guffey

 

[fguffey]

For the curious, the testing done with 133 with a out of the can charge weight of 28 grains showed a moisture content of 1.1%, which dried to .5% just sitting in open cases in the authors basement.

Curious? I believe I could do that if I heated the case. I can not believe the air in the basement was dry enough to absorb moisture. I would have suggested he look for another reason for the difference in weight.

F. Guffey

 

[BoydAllen]

Frank,
That is the point of doing actual testing.
Something that many seem not to understand is that experiments can yield unexpected results, and when they do, our knowledge is increased. He described his basement as rather dry. He lives in Colorado.

 

[JRS]

You'll find a substantial article on the subject in the NORMA Reloading Manual.

 

[fguffey]

Boyd Allen, I understand relative humidity, wet bulb etc.. It is difficult to see sweat in the Mojave, it is difficult to get rid of it in Houston, I know, that is the reason they say: "But it's dry heat".

F. Guffey

 

[Brians356]

What's next??

Letting your brass.....REST??

Its called destressing. Its the next fad coming during the cabin fever season coming up

College kids today, hypersensitive and ever vigilant (especially girls), can be victims of "trigger" events or comments (even "microaggressions" such has being addressed as "miss" so-and-so), and colleges are providing "safe spaces" where they can play with dolls or curl up in fetal positions to recover their sense of empowerment. I kid you not.

 

[Brians356]

Frank,
That is the point of doing actual testing.
Something that many seem not to understand is that experiments can yield unexpected results, and when they do, our knowledge is increased. He described his basement as rather dry. He lives in Colorado.

I wonder what the RH is inside the canister when the powder is packed? A basement may be dry, but household activity (cooking, bathing) and the presence of expirating humans renders most indoor spaces with RH near 50% even in dry climes such as here in NV. (Indoor RH obviously can vary widely by region, season, and heating/cooling systems.) The presence of an inverted loading block over the cases was probably helpful. It's a coin flip whether I'd shoot them, not for safety reasons so much as they may have shifted burn rate enough to taint any test results, so why bother?

 

[savagedasher]

Frank,
That is the point of doing actual testing.
Something that many seem not to understand is that experiments can yield unexpected results, and when they do, our knowledge is increased. He described his basement as rather dry. He lives in Colorado.

I wonder what the RH is inside the canister when the powder is packed? A basement may be dry, but household activity (cooking, bathing) and the presence of expirating humans renders most indoor spaces with RH near 50% even in dry climes such as here in NV. (Indoor RH obviously can vary widely by region, season, and heating/cooling systems.) The presence of an inverted loading block over the cases was probably helpful. It's a coin flip whether I'd shoot them, not for safety reasons so much as they may have shifted burn rate enough to taint any test results, so why bother?

What is a Basement? ;D Larry

 

[Brians356]

What is a Basement? ;D

A root cellar to you, possibly. Or coal bin. No, wait, you in FL? Storm shelter.

 

[savagedasher]

What is a Basement? ;D

A root cellar to you, possibly. Or coal bin. No, wait, you in FL? Storm shelter.

Nothing below the ground. ;D That I have ever seen . Most where I live cant dig a hole 15 '' with out water. ;D Larry

 

[Brians356]

What is a Basement? ;D

A root cellar to you, possibly. Or coal bin. No, wait, you in FL? Storm shelter.

Nothing below the ground. ;D That I have ever seen . Most where I live cant dig a hole 15 '' with out water. ;D Larry

Then what do you do for cemeteries? Put 'em up on scaffolds, like the plains tribes?

 

[jlow]

I suggest that you read the article. The author's results for H322 in a PPC were that freshly opened powder (25 gr. charge wt.) contained .9% moisture. The powder that that was dried in the cases became .9% lighter. The powder that was humidified at 66 degrees came up to a moisture content of 1.8%. Humidification at a higher temperature (102 degrees) increased moisture content to 2%. Drying the powder increased the average velocity (compared to loads using freshly opened powder) from 2,892 fps to 3050 fps., a change of 158 fps. which is a little over 5%. The powder that was humidified at 66 degrees lost 159 fps (compared to loads using freshly opened powder). The powder that was humidified a the higher temperature, to 2% moisture lost 195 fps. Taking the extremes from fully dried to humidified at 102 degrees, the difference in average velocities was 353 fps. Just sitting around open in his basement lowered the out of container moisture content from .9% to .5% for a change in velocity of 98 fps. From these results it can be see that changes in the velocities do not track with simple changes in the weights of charges. Consulting 6PPC data in my Berger manual, for 68 grain bullets, the average computed increase of velocity per grain of 322 works out to be 111 fps. The maximum difference of charge weights for this powder in the test for this cartridge and powder was 2% which was roughly a weight difference (starting with a 25 grain charge) of approximately half of a grain. If changes in observed velocity were only based on differences in charge weight the they would have been about 55 fps at the extreme. This is the reason that this article is so important. Comparing dry powder to the most humidified, a weight change due to moisture, of 2% produced a velocity difference of 13%.

For the curious, the testing done with 133 with a out of the can charge weight of 28 grains showed a moisture content of 1.1%, which dried to .5% just sitting in open cases in the authors basement. This resulted in a a velocity increase of 87 fps from that .6% moisture change. Looking at the extremes, a 1.8% difference from dry to wet (@66 degrees) the difference in average velocities was 233 fps. The humidification at a higher temperature was not done with this powder.

Thanks Boyd. I think as usual with these cases, there are more than one thing going on, so increase in weight due to moisture content would be one but perhaps the moisture also retard the rate/degree of combustion. Regardless, what is in the article would be the worst case scenario. With the OP, it cannot be the worst case since the water weight is not a factor and so can be taken completely out of the equation. So whatever is left may have an effect but then you are still talking about super moist vs. absorption some moisture. My gut feeling is that safety is not an issue but the OP’s rounds may end up being slightly slower. Of course as in all cases like this, everyone has to decide what they think is safe and go forward with their own decision.