Need Input on Maximum Wet Bulb or Dewpoint Temp for Reloading

[TexasMP40]

Does anyone know of at what point the wet bulb or dewpoint are too high that would negatively effect reloading?

I used the terms wet bulb or dew point, because I keep seeing posts using relative humidity.
The true indicators of how much moisture is actually in the air are related to wet bulb, dewpoint, grains of moisture/lb of dry air, etc.

Unfortunately, relative humidity (RH) is basically a useless term, since it changes in relation to the dry bulb temperature.
With same amount moisture present, as the air temperature (dry bulb) decreases the relative humidity increases and vice versa.
With air at a wet bulb of 55 degrees and an air temperature (dry bulb) of 100, the relative humidity is about 22%, but the same air with an air temperature (dry bulb) of 55, the relative humidity is 100%.
You can't compare 50% RH in Colorado with dry bulb temps in mid teens to the Gulf Coast with dry bulb temps in the upper 90's.

I'm just trying to determine at what point there is too much moisture present to reload.

 

[jpmimproved]

I don’t know that I’d go as far as to say relative humidity is a useless term, as it’s merely a calculated value from the dry bulb and wet bulb temperatures. If you get a psychrometric chart, any two values factors can find you the third. I’m assuming you are loading outdoors? If not, I’d be a lot more focused on other factors than the humidity.

 

[MClark]

I used to make solid propellant rocket motors for ejection seats. If I remember correctly the max wet bulb was around 45 f. We did not go very low because of static. Was a balance between keeping moisture out of the propellant and not blowing up.

As you stated relative humidity number by itself is useless.

Gunpowders should be less hydroscopic. But lower the better within reason.

 

[RegionRat]

It was too long ago to remember the water content we standardized on, but the air was something close to 9 grams per cubic meter during typical loading conditions near 68 F.

You are correct about the water content, but RH was more than good enough when it came to controlling powder water content in the labs and factories. It is what we use.

Here is an excerpt from that Norma Manual in the write up by @mc10


https://chronoplotter.com/2021/08/19/how-does-humidity-affect-powder/

The best thing I would advise, is to find your most common condition. The one that takes the least trouble to control, and normalize your powder and ammo velocity tests there. There is no right or wrong value, so you can pick any arbitrary goal.

For most of us who pay attention to batch to batch controls, we try to stay within 45 - 55% and 67 - 69 degrees F.

There are many other factors that can cause batch to batch velocity drifts, including the example of getting the water content within your tolerance and yet finding the new batch of powder still has a different burn rate than the one before.

 

[Mulligan]

It was too long ago to remember the water content we standardized on, but the air was something close to 9 grams per cubic meter during typical loading conditions near 68 F.

You are correct about the water content, but RH was more than good enough when it came to controlling powder water content in the labs and factories. It is what we use.

Here is an excerpt from that Norma Manual in the write up by @mc10

View attachment 1277843
https://chronoplotter.com/2021/08/19/how-does-humidity-affect-powder/

The best thing I would advise, is to find your most common condition. The one that takes the least trouble to control, and normalize your powder and ammo velocity tests there. There is no right or wrong value, so you can pick any arbitrary goal.

For most of us who pay attention to batch to batch controls, we try to stay within 45 - 55% and 67 - 69 degrees F.

There are many other factors that can cause batch to batch velocity drifts, including the example of getting the water content within your tolerance and yet finding the new batch of powder still has a different burn rate than the one before.

Good info ^^^^^
I read that VV powder company targets 50% RH in the mfg of their powders.
CW

 

[Jager]

RH and temperature are tightly bound. If you control temperature to a very small range, such as might be the case in a laboratory or other fixed environment, RH is a perfectly good measure for assessing air moisture. But if temperature varies a bit - such as the upstairs bedroom where I do my handloading (no heat in the winter; window AC unit in the summer), RH can easily be misleading.

I use dew point as my measure of moisture that smokeless powder is exposed to, as that automatically adjusts to temperature.

I load ammo year-round. My general thinking is that environmentals that are comfortable enough to sit in are probably okay to load in.

I typically see dew points in the mid 50’s to low 60’s. I don’t yet have enough empirical data to support any downrange conclusions.

 

[ballisticxlr]

I try to do my loading in 40-60% humidity in 60-70F temps. That temperature range is comfortable to load in and that humidity range is the "normal" range for where I live. Those being the cases, I basically never worry about it because I don't go reloading when it's uncomfortable conditions to do so.