Advanced musings on powder humidity

[secondofangle2]

I've been using humidity packs in my powder for about 2 years. Was at range the other day, shooting 50 BMG reloads, 2865 fps, SD<10, all good just like usual. Used up that batch, opened a new batch of reloads (marked on the label "RH 49%), velocity fell almost 100 fps average, and the SD was ALL over the place. I'm like WTF, tore them apart when I got home, the charges were all correct. Then I noticed the date of reloading: 7/6/2023. Here's one POSSIBILITY of what happened.

There were 4 humidity packs in the 8# jug of RL50 I used last summer and am still using. If I put them in the new jug when I started the reloading session, out in my garage with 100 degree temperatures, the 49% humidity packs would start releasing moisture to get to the 49% RH. Moreover, if it had not sat/mixed long enough, the powder may have uneven humidity, with granules close to the packs having more moisture until full mixing occurred. Who knows what the distribution of humidity was if it was inadequately mixed by the time it got into the Superspiller hopper.

I had not paid enough attention to what happens to absolute water content when temperature changes at a constant relative humidity. The water content goes up something like 5x or more if you go from 50 degrees to 100 degrees at a constant RH. See: https://brownell.co.uk/datasheets/basics_humidity.pdf

I'm not SURE this was the source of my problem, but I realized the humidity packs could be a HUGE mistake if you have temperature changes in your powder (I store mine in the basement and reload in the garage which varies markedly in temperature throughout the year).

If I want the water content of the powder to remain constant, I have to keep the temperature constant when those packs are in place. In my basement it's almost always 60-70 degrees year round. Humidity packs in the powder are fine down there, but if I take the powder to the garage in summer, the packs are going to immediately (and unevenly) start releasing moisture since the hotter air in the container can contain more moisture at a constant RH. Conversely, if I go out in the garage and it's below freezing, the RH in the container will go up, and the packs will start removing moisture from the powder. So I should always remove the packs prior to reloading, and replace for storage, is what I'm thinking. At least if the ambient reloading temperature is significantly different from where the powder has been stored.

The other thing is I'm going to start recording both the temperature I reloaded at and the RH of the powder (measured by Kestrel drop) at the time of reloading.

Finally, the amount of water in an 8# jug is pretty minuscule, so even large relative changes in water content do not cause big absolute changes. However, all the "experimental" evidence guys have posted seems to suggest it does make a difference.

Interested in any thoughts especially from engineering/physics/chemistry types.

Here is a link that allows you to calculate water content based on temperature and RH: https://www.lenntech.com/calculators/humidity/relative-humidity.htm

 

[JerkyFreak]

Finally someone gets it. Reloading should be done in a climate controlled area if you are worried about humidity changes in your powder.

Personally I reload between 20 to 25°C and between 50-55%RH. Outside those limits I either selectively use the AC and humidifier, or I wait until conditions are better. Ever since I started doing that, my batch-to-batch consistency has become much better.

 

[ma smith]

Good thread OP.

 

[Doom]

I've been using humidity packs in my powder for about 2 years. Was at range the other day, shooting 50 BMG reloads, 2865 fps, SD<10, all good just like usual. Used up that batch, opened a new batch of reloads (marked on the label "RH 49%), velocity fell almost 100 fps average, and the SD was ALL over the place. I'm like WTF, tore them apart when I got home, the charges were all correct. Then I noticed the date of reloading: 7/6/2023. Here's one POSSIBILITY of what happened.

There were 4 humidity packs in the 8# jug of RL50 I used last summer and am still using. If I put them in the new jug when I started the reloading session, out in my garage with 100 degree temperatures, the 49% humidity packs would start releasing moisture to get to the 49% RH. Moreover, if it had not sat/mixed long enough, the powder may have uneven humidity, with granules close to the packs having more moisture until full mixing occurred. Who knows what the distribution of humidity was if it was inadequately mixed by the time it got into the Superspiller hopper.

I had not paid enough attention to what happens to absolute water content when temperature changes at a constant relative humidity. The water content goes up something like 5x or more if you go from 50 degrees to 100 degrees at a constant RH. See: https://brownell.co.uk/datasheets/basics_humidity.pdf

I'm not SURE this was the source of my problem, but I realized the humidity packs could be a HUGE mistake if you have temperature changes in your powder (I store mine in the basement and reload in the garage which varies markedly in temperature throughout the year).

If I want the water content of the powder to remain constant, I have to keep the temperature constant when those packs are in place. In my basement it's almost always 60-70 degrees year round. Humidity packs in the powder are fine down there, but if I take the powder to the garage in summer, the packs are going to immediately (and unevenly) start releasing moisture since the hotter air in the container can contain more moisture at a constant RH. Conversely, if I go out in the garage and it's below freezing, the RH in the container will go up, and the packs will start removing moisture from the powder. So I should always remove the packs prior to reloading, and replace for storage, is what I'm thinking. At least if the ambient reloading temperature is significantly different from where the powder has been stored.

The other thing is I'm going to start recording both the temperature I reloaded at and the RH of the powder (measured by Kestrel drop) at the time of reloading.

Finally, the amount of water in an 8# jug is pretty minuscule, so even large relative changes in water content do not cause big absolute changes. However, all the "experimental" evidence guys have posted seems to suggest it does make a difference.

Interested in any thoughts especially from engineering/physics/chemistry types.

Here is a link that allows you to calculate water content based on temperature and RH: https://www.lenntech.com/calculators/humidity/relative-humidity.htm

You have learned the fallacy of blindly looking at humidity. The other item that you need to come to grips with is that putting powder in a measure in a ? humidity room does not magically change the humidity to ?. It is a mass transfer phenomena and takes time to occur. You powder in the fixed HDPE container also changes very little if any with variations in room RH. If the powder is keep in a place like Tuscon or Seattle then it will eventually acclimate to those humidities.

 

[straightshooter1]

I've been using humidity packs in my powder for about 2 years. Was at range the other day, shooting 50 BMG reloads, 2865 fps, SD<10, all good just like usual. Used up that batch, opened a new batch of reloads (marked on the label "RH 49%), velocity fell almost 100 fps average, and the SD was ALL over the place. I'm like WTF, tore them apart when I got home, the charges were all correct. Then I noticed the date of reloading: 7/6/2023. Here's one POSSIBILITY of what happened.

There were 4 humidity packs in the 8# jug of RL50 I used last summer and am still using. If I put them in the new jug when I started the reloading session, out in my garage with 100 degree temperatures, the 49% humidity packs would start releasing moisture to get to the 49% RH. Moreover, if it had not sat/mixed long enough, the powder may have uneven humidity, with granules close to the packs having more moisture until full mixing occurred. Who knows what the distribution of humidity was if it was inadequately mixed by the time it got into the Superspiller hopper.

I had not paid enough attention to what happens to absolute water content when temperature changes at a constant relative humidity. The water content goes up something like 5x or more if you go from 50 degrees to 100 degrees at a constant RH. See: https://brownell.co.uk/datasheets/basics_humidity.pdf

I'm not SURE this was the source of my problem, but I realized the humidity packs could be a HUGE mistake if you have temperature changes in your powder (I store mine in the basement and reload in the garage which varies markedly in temperature throughout the year).

If I want the water content of the powder to remain constant, I have to keep the temperature constant when those packs are in place. In my basement it's almost always 60-70 degrees year round. Humidity packs in the powder are fine down there, but if I take the powder to the garage in summer, the packs are going to immediately (and unevenly) start releasing moisture since the hotter air in the container can contain more moisture at a constant RH. Conversely, if I go out in the garage and it's below freezing, the RH in the container will go up, and the packs will start removing moisture from the powder. So I should always remove the packs prior to reloading, and replace for storage, is what I'm thinking. At least if the ambient reloading temperature is significantly different from where the powder has been stored.

The other thing is I'm going to start recording both the temperature I reloaded at and the RH of the powder (measured by Kestrel drop) at the time of reloading.

Finally, the amount of water in an 8# jug is pretty minuscule, so even large relative changes in water content do not cause big absolute changes. However, all the "experimental" evidence guys have posted seems to suggest it does make a difference.

Interested in any thoughts especially from engineering/physics/chemistry types.

Here is a link that allows you to calculate water content based on temperature and RH: https://www.lenntech.com/calculators/humidity/relative-humidity.htm

How did you store those cartridges since Jul 2023?

Unless the primer pockets are sealed and the neck is also sealed, the cartridges can leak pulling in outside air or pushing out the interior air. That is, there can be an exchange of atmosphere within the cartridge with the outside atmosphere depending on temperature differentials occurring as well as with barometric pressure changes.

 

[secondofangle2]

^ I have already posted about that experiment elsewhere.

I filled a 375 Cheytac case with water two years ago and it has not lost even a fraction of a grain. I weigh it every couple of months on an FX – 120i scale.

You can search for my post, but it is an unsealed new primer seated in a case fired multiple times and the bullet is seated with just a little bit of lanolin lube on it

So, no, under ordinary circumstances, moisture neither enters nor exits a loaded cartridge case

ETA: it is sitting on the bench in the garage with temperatures ranging from well below freezing to over 100° during those two years and the relative humidity tends to be between 20 and 40%, which ought to be plenty of gradient for water to exit that case

 

[Rocketmandb]

This is why I want to build a great big house. Inside that house will be a great big room. The room will have a great big humidity controller and its own great big temperature controller. This will be my great big reloading room.

 

[TheOE800]

Ammo humidors bro, I’m telling you that’s the next big precision rifle thing.

 

[straightshooter1]

^ I have already posted about that experiment elsewhere.

I filled a 375 Cheytac case with water two years ago and it has not lost even a fraction of a grain. I weigh it every couple of months on an FX – 120i scale.

You can search for my post, but it is an unsealed new primer seated in a case fired multiple times and the bullet is seated with just a little bit of lanolin lube on it

So, no, under ordinary circumstances, moisture neither enters nor exits a loaded cartridge case

ETA: it is sitting on the bench in the garage with temperatures ranging from well below freezing to over 100° during those two years and the relative humidity tends to be between 20 and 40%, which ought to be plenty of gradient for water to exit that case

That's really and apple to oranges kind of thing. You're looking as the results of water in it's liquid state instead of water in its gaseous state. BIG difference.

 

[6.5SH]

I've been using humidity packs in my powder for about 2 years. Was at range the other day, shooting 50 BMG reloads, 2865 fps, SD<10, all good just like usual. Used up that batch, opened a new batch of reloads (marked on the label "RH 49%), velocity fell almost 100 fps average, and the SD was ALL over the place. I'm like WTF, tore them apart when I got home, the charges were all correct. Then I noticed the date of reloading: 7/6/2023. Here's one POSSIBILITY of what happened.

There were 4 humidity packs in the 8# jug of RL50 I used last summer and am still using. If I put them in the new jug when I started the reloading session, out in my garage with 100 degree temperatures, the 49% humidity packs would start releasing moisture to get to the 49% RH. Moreover, if it had not sat/mixed long enough, the powder may have uneven humidity, with granules close to the packs having more moisture until full mixing occurred. Who knows what the distribution of humidity was if it was inadequately mixed by the time it got into the Superspiller hopper.

I had not paid enough attention to what happens to absolute water content when temperature changes at a constant relative humidity. The water content goes up something like 5x or more if you go from 50 degrees to 100 degrees at a constant RH. See: https://brownell.co.uk/datasheets/basics_humidity.pdf

I'm not SURE this was the source of my problem, but I realized the humidity packs could be a HUGE mistake if you have temperature changes in your powder (I store mine in the basement and reload in the garage which varies markedly in temperature throughout the year).

If I want the water content of the powder to remain constant, I have to keep the temperature constant when those packs are in place. In my basement it's almost always 60-70 degrees year round. Humidity packs in the powder are fine down there, but if I take the powder to the garage in summer, the packs are going to immediately (and unevenly) start releasing moisture since the hotter air in the container can contain more moisture at a constant RH. Conversely, if I go out in the garage and it's below freezing, the RH in the container will go up, and the packs will start removing moisture from the powder. So I should always remove the packs prior to reloading, and replace for storage, is what I'm thinking. At least if the ambient reloading temperature is significantly different from where the powder has been stored.

The other thing is I'm going to start recording both the temperature I reloaded at and the RH of the powder (measured by Kestrel drop) at the time of reloading.

Finally, the amount of water in an 8# jug is pretty minuscule, so even large relative changes in water content do not cause big absolute changes. However, all the "experimental" evidence guys have posted seems to suggest it does make a difference.

Interested in any thoughts especially from engineering/physics/chemistry types.

Here is a link that allows you to calculate water content based on temperature and RH: https://www.lenntech.com/calculators/humidity/relative-humidity.htm

These are cheap enough to keep one in your hopper and whatever container(s) of powder you are actively using. They store 20 days of data in a rolling log and are pretty easy on the battery. Beats moving a Drop around IMO.

Amazon.com

 

[Huskydriver]

I've been using humidity packs in my powder for about 2 years. Was at range the other day, shooting 50 BMG reloads, 2865 fps, SD<10, all good just like usual. Used up that batch, opened a new batch of reloads (marked on the label "RH 49%), velocity fell almost 100 fps average, and the SD was ALL over the place. I'm like WTF, tore them apart when I got home, the charges were all correct. Then I noticed the date of reloading: 7/6/2023. Here's one POSSIBILITY of what happened.

There were 4 humidity packs in the 8# jug of RL50 I used last summer and am still using. If I put them in the new jug when I started the reloading session, out in my garage with 100 degree temperatures, the 49% humidity packs would start releasing moisture to get to the 49% RH. Moreover, if it had not sat/mixed long enough, the powder may have uneven humidity, with granules close to the packs having more moisture until full mixing occurred. Who knows what the distribution of humidity was if it was inadequately mixed by the time it got into the Superspiller hopper.

I had not paid enough attention to what happens to absolute water content when temperature changes at a constant relative humidity. The water content goes up something like 5x or more if you go from 50 degrees to 100 degrees at a constant RH. See: https://brownell.co.uk/datasheets/basics_humidity.pdf

I'm not SURE this was the source of my problem, but I realized the humidity packs could be a HUGE mistake if you have temperature changes in your powder (I store mine in the basement and reload in the garage which varies markedly in temperature throughout the year).

If I want the water content of the powder to remain constant, I have to keep the temperature constant when those packs are in place. In my basement it's almost always 60-70 degrees year round. Humidity packs in the powder are fine down there, but if I take the powder to the garage in summer, the packs are going to immediately (and unevenly) start releasing moisture since the hotter air in the container can contain more moisture at a constant RH. Conversely, if I go out in the garage and it's below freezing, the RH in the container will go up, and the packs will start removing moisture from the powder. So I should always remove the packs prior to reloading, and replace for storage, is what I'm thinking. At least if the ambient reloading temperature is significantly different from where the powder has been stored.

The other thing is I'm going to start recording both the temperature I reloaded at and the RH of the powder (measured by Kestrel drop) at the time of reloading.

Finally, the amount of water in an 8# jug is pretty minuscule, so even large relative changes in water content do not cause big absolute changes. However, all the "experimental" evidence guys have posted seems to suggest it does make a difference.

Interested in any thoughts especially from engineering/physics/chemistry types.

Here is a link that allows you to calculate water content based on temperature and RH: https://www.lenntech.com/calculators/humidity/relative-humidity.htm

What's interesting is I have several different styles of air sensors in my home. They all agree that regardless of the season barring actually storms that roll through, my house stays pretty much around 30% rh all year long.

I have played around with just letting powder sit out from a fresh container for 3,5,7,10,14,30,60 days then loading and chronoing it. Fresh powder is always slower or seems.

... Every time I have run this anecdotal experiment regardless of it's winter or summer, seems like after day 10-12 the powder stops speeding up but to achieve that mv after day 12 requires a couple tenths of a grain extra.

My layman hypothesis is that as that powder reaches homeostasis with the Utah air and losses that water weight, and without changing the desired charge weight, there's less water mass so it takes a couple tenths of a grain to equal the same charge as the stating fresh powder.

Could be completely wrong but it seems to be consistent going on 2 years this winter.

If that's the case what's the advantage holding the powder at a rh vs just letting it acclimate ?

 

[JerkyFreak]

In South Africa, the powder is packed at around 50% RH at 25°C. Less than 40% static becomes a problem. More than 60% the powder burn rate slows way down. For those reasons I presume other manufacturers follow a similar procedure.

That would explain why your "fresh powder" at +- 50% RH would be slower that your acclimatized powder at 30% RH. You probably also have some challenges with static on your powder dispensers.