Powder humidity changes inside loaded cartridges

[Ex E6]

An older refrigerator works very well indeed plugged in or not . The key is placing your original container of powder into a secondary plastic bag and sealing it . This method helps retain RH rather than increasing or losing it .

A frost free freezer operating at 0 F. has around 38–42% humidity. When the freezer goes into the defrost cycle about every 12 hours for around 20 minutes, the temperature will rise about 10 Deg.F. and the humidity will rise to about 70–80%. Around four hours is required to drive that temperature and humidity back down again.
The defrost cycle has about the same effect on temperature and humidity as opening the door on a hot, 95 degree day to get something out of the freezer. However, it only takes about 90 minutes to drive the temperature and humidity back down after closing the freezer door.

So if one was to find an older chest freezer ,you'd have a relatively stable RH storage in a powder magazine of sorts .
Depending upon your particular area and it's normal RH ,would dictate either secondary wrapping and or plugging the freezer or Refrigerator in .

 

[JerkyFreak]

What people should consider is that combustion properties change with humidity. Between 45% and 55% the change in muzzle velocity for an uncompressed .308win load is reasonably small and predictable. Below 40% and above 60% the changes become progressively larger. The above is only true for extruded powders. Ball powders are much less affected as far as I know.

Another thought; below 40% RH you get more problems with static electricity. Above 45% static is usually a non-issue.

 

[Ex E6]

What people should consider is that combustion properties change with humidity. Between 45% and 55% the change in muzzle velocity for an uncompressed .308win load is reasonably small and predictable. Below 40% and above 60% the changes become progressively larger. The above is only true for extruded powders. Ball powders are much less affected as far as I know.

Another thought; below 40% RH you get more problems with static electricity. Above 45% static is usually a non-issue.

Ball powders are Dbl based and relatively speaking are unaffected by RH .

One thing many shooters are forgetting is : You've been working up YOUR loads with out worrying about RH for decades and as such have compensated for atmospheric differences in particular regions . Hence along with chamber and barrel variations is WHY shooters loads vary , in addition to charges varying suitable velocities for individual preferences .

 

[Fred @ Bison Tactical]

Right now (Spring) in the Denver CO area we have 24% humidity (according to my Kestrel). I think we range somewhere from 15% - 60%.

I think I am going to change from the normalizing method of decreasing the humidity content of the powder, to stabilizing it at 49%.

The goal for me is more consistency, so making sure to never leave out powder, and keep the containers sealed with humidity packs seems like a safer way to keep the powder consistent.