Powder changing property if loads made during real humid weather

[Jack R Tishue Jr]

A friend just ask if I'd post the question. He was going to reload this past weekend, but here (MD), the heat in the 90s and the humidity at 70+%. I told him in my opinion (I ve been reloading 60 years now), the amount of time your powder would be exposed to the moisture in the air, while loading probably wouldn't be long enough to contaminate it. BUT, told him I'd post the question here for folks to respond to, and give us their information. Thanks.. This with modern Smokeless powder, not real old time BP.

 

[MagnumManiac]

Modern powder is almost water proof with all the coatings, flash suppressors and flame retardants.

Fun fact; IMR have original recipe 4198 stored in a jar filled with water, every so often, they remove some, dry it out and test it against new batches to see if the new recipe compares.
Humudity is rarely a problem with powder, temperature swings in storage are the culprit in most degradation issues.

Cheers.

 

[ShtrRdy]

I've been wondering about this too. The thought being that when we reload we usually dump powder from the bottle into a hopper. The powder is then exposed to the air around it. If the powder is able to absorb or displace water from the air it could change the weight and/or volume of the powder. This, in turn, could change the amount of energy a "charge" of powder would have.

I found this article which describes an affect:
http://bulletin.accurateshooter.com/2018/03/humidity-and-powder-burn-rates-what-you-need-to-know/