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 its 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.

 

[Huskydriver]

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.

0 static issues that I can tell but I do have my bench and all the equipment grounded including my thrower etc so maybe that's why?

 

[JR1200W3]

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

Where do you live? Aren't you in Utah?

 

[Emerson0311]

Rimfire ammo seems especially vulnerable to outdoor humidity fluctuations. Just drag conditions? Powder burn rate? Anyway, high humidity lower velocity seems to be a thing?

 

[jthor]

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

I’ve been putting humidity packs in my powder for about the same time. Recently I’ve made these 3D printed humidity pack holders. Red part is PLA plastic and the black part is TPU (Rubber).

 

[JR1200W3]

The powder is going to perform the drier it gets. When it acclimatizes to Colorado and Utah air you'll get higher velocities and better SDs. Putting dessicant packs in your powder out here is dumb. You're far better off leaving the lid off for about a week. Or even pouring it out in a turkey basting tin for 3 days. Trying to fight it out here just ends up with constant dicking with it for no good reason. It'll perform better with Colorado acclimatization. Try it. Pour a half a cup into an open container like a glass bowl and leave it in your house in a controlled temp room for three days, load it and shoot it.

And ask Steve Eames about drying powder if you want. That will really make your head explode.

 

[jthor]

My 31.7 of RL15.5 in my dasher has been pretty consistent at 2860 for 2 barrels now with using the 49% humidity packs.

I actually started using it because of Colorados weather. I would get faster speeds oddly enough in the winter and have to drop my powder charge and then slower in the summer. I equated that to the winters having a lot less humidity and then the summers having more. Once I put the humidity packs in my powder that all stopped.

 

[JR1200W3]

I haven't had swings like that in my Dasher since acclimatizing my powder. I discovered it by leaving powder in a hopper for two months in the winter and went to a match with 105's going 3060fps. Right after that I developed a load for a 6BR barrel going 2800fps. I had to open a new jug and the same charge was going just under 2700 with pressure. I left it out for 3 days and gained 90fps and the pressure went away. Then I read a FB from Steve Eames where he was talking about laying 16lbs of Varget out in the sun in the summer in Utah to dry his powder out.

I initially acclimatize my powder when the RH is around 25-28% which seems to be 90% of the year. Only during periods like this week do you see the humidity over 30. Once it's acclimatized you can simply pour it back in the jug and recap it. Even though the jug doesn't completely seal it, it retards the swings significantly. I haven't had major swings in velocity doing it this way, when I'm able to have one load for over 12 months. I'm more likely to shoot a barrel out, have a barrel speed up, or see a slight decline in velocity due to lands eroding.

It could be the case that once you started paying attention to how you handled your powder, that alone was the consistency required to eliminate the swings. And you can get the same results trying to control the moisture content at a random % or at your relative %.

 

[jthor]

Im not against trying that. I have several 1lb containers I could off load some of my 15.5 in and then try some that’s been dried to the RH you spoke of.

 

[JR1200W3]

Im not against trying that. I have several 1lb containers I could off load some of my 15.5 in and then try some that’s been dried to the RH you spoke of.

When you say you saw velocity swings from winter to summer or vice versa....how did you treat the powder then? Did you pour it out and acclimatize it? Start at a base line? Or did you just open the jug, load and close the jug, shoot, open -> load -> close -> shoot, etc? Were the swings you saw from a long, continual acclimatization from a new jug to a year later of using the powder? Because I think it would be hard to say what the swings were from if the powder hadn't homogenized in the first place.

 

[Baron23]

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

Yep, that's why they call it RELATIVE humidity.

 

[jthor]

When you say you saw velocity swings from winter to summer or vice versa....how did you treat the powder then? Did you pour it out and acclimatize it? Start at a base line? Or did you just open the jug, load and close the jug, shoot, open -> load -> close -> shoot, etc? Were the swings you saw from a long, continual acclimatization from a new jug to a year later of using the powder? Because I think it would be hard to say what the swings were from if the powder hadn't homogenized in the first place.

Then it was just open, load hopper, close and then shoot. I was shooting a match once a week that year and noticed it. Didn’t really know what to do to fix it at the time until I saw something somewhere about the powders humidity changing the burn rate/characteristics. That’s when I tried the humidity packets and then redid load dev after a week. That’s when I started getting consistent velocities from one week to the next.

 

[JR1200W3]

Then it was just open, load hopper, close and then shoot. I was shooting a match once a week that year and noticed it. Didn’t really know what to do to fix it at the time until I saw something somewhere about the powders humidity changing the burn rate/characteristics. That’s when I tried the humidity packets and then redid load dev after a week. That’s when I started getting consistent velocities from one week to the next.

Ya, so your powder was in the process of acclimatization. I wonder how many people out west confuse barrels speeding up with powder speeding up when they get a new barrel/ cartridge, buy a jug of powder for it and start loading(repeatedly exposing the powder).

I don't fight it now. I lean into it. I dump an entire jug in a pan for three days and then repackage it. Just eliminates one variable. And it's a one time deal. I don't have to worry about getting the beans above the franks like the OP.

 

[JR1200W3]

Well, the OP long ago blocked you and for good reason.

Oh and this is not referring to Thor, it’s the retard

I know you're not going to see this, but your musings aren't advanced. You're just doing the equivalent of sorting primers by weight with powder. But you definitely think you're smart, and have the idea that if you do it then it's advanced. But it doesn't have to be that complicated. You're overcomplicating it and tripping over yourself. Hence your opening post. You make my case for me. It's the definition of not getting out of your own way.