During a renovation, I had to abandon my reloading room for a few months.(talk about a low point in life). Anyway, I neglected to empty my powder charger. How long can I leave powder in this state without drawing moisture? The room is conditioned - 72 degrees @ 45% humidity. Just not sure if I trust the powder anymore. It's about 1/3 of an RCBS charger full.

Dump it, how can you remember what type of powder it is after so long?

Thanks for the reminder - really,really good point! But...... I spend about two years on load development for each of my calibers, so I know it's IMR 4895.I was only about 6 months into a load at the time. Yes, I'd bet my life on that. Just wasn't sure how quickly powder draws moisture.

Your posting reminded me of a funny event relating to old powder.
Back when I still enjoyed abuse I was married. Now days I let my rifles abuse me it's more productive. Any way I had broken down and emptied a bucket full of misfires, bad loads, etc to get the brass and bullets back for reuse, they were all cast bullets.
I dumped the powder into a cofee can and when finished I spread the powder on my wife's Ageratum and daffidil flower bed. This was January, I figured the powder would break down and make fertilizer.
Now it's May, my wife has her friends over for bridge, I'm exiled to the back yard. "Don't want to let the ladies associate with the ruffian I married, you know."
Well I decided to cast bullets on the patio, ajoining the flower bed mentioned above. Said flower bed is under the kitchen where a table of ladies are playing bridge.
As you know while casting lead you need to flux the molten lead to clean it off. Well I'd throw the flaming slag over in the flower bed, figuring I'd pick it up in the morning and throw it away. All was going well until I got a bit enthusiastic in my pitching the flaming slag.
Well a wall of flame about 5 feet tall and 12 feet long shot down my wife's flower bed incinterating all of her daffidils and ageratum. The ladies were a bit taken aback by the sudden flash of light. The flash lit up the whole back yard, I was momentarily blinded the cats made themselves real scarce. Then I began to laugh.
The wife was not pleased with the late night weeding, but she eventually saw the humor.
Jim

Powder is cheap enough, dump it. Moisture levels vary results....why bother?

SP

The moisture content of powder varies pretty quickly with that of the ambient air. If you pour some 4895 out of the cannister into an open container along side the "exposed" 4895, both will have a similar moisture content in a few hours. (By the way, one reason many people believe volumetric measuring frequently yields better consistency than weight measuring is that the volumentric method doesn't change the amount of powder going into the load dependent on its moisture content.)

Since you spent so much time in load development, you must know the performance of this powder pretty well. Simply load some of it and check its performance now versus what you were getting 6 months ago. That should answer your questions.

I got a simple rule. Powder goes in the hopper, can goes on the shelf behind it. Stop for an hour that turns into week or two and the can for the powder in the hopper is right there.

I also don't worry much about humidity and smokeless powder. Ain't a benchrester and don't think it makes a difference for my purposes.

Somebody more obsessive than me might want to weigh out 100 grains of several powders, leave them out a few weeks and see if the weight changes significantly. With a cloth or filter paper cover to keep out dust, a change of more than one percent would surprise me.

I wouldn't worry one bit about that powder absorbing moisture from the air. One company (Alliant, I think) has old batches of powder they've stored in water for 50 or 100 years or something, and they just dry it out every so often to test it. It still shoots good. This old powder was made before modern stabilizers (e.g. diphenylamine) were incorporated into smokeless powders.

What I would worry about is this. When you open a can of that powder, you can smell a nice alcohol odor. When all that alcohol has evaporated from the powder, those powder grains are going to be that much more hard and/or brittle. If the hardness or brittleness of the powder grains causes the grains to break up slower or faster while they burn, the powder overall could burn slower or faster than you're used to.

Half a pound of powder probably cost you $8.00. How many nice jacketed bullets will you fire without confidence in your loads before those bullets would have paid for another half a pound of powder.

I believe the world is so safety obsessed that there is an unnecessarily large margin of safety around every product on the market, including gunpowder. I'd still chuck that powder. I understand it makes good fertilizer.

H. C.