777 pellets and moisture

How hydroscopic do you find 777 pellets to be?

I shot a bunch yesterday from my speedloaders (loaded last year) to get rid of them and litterly was all over the place. Same thing happened last year. Broke out the ones I sealed in a plastic bag in the box, and back to 2MOA accuracy.

I know any blackpowder or pyrodex product, can collect moisture. Just didn't think 777 pellets would. Velocity was also all over. After two years, same thing, I think they are prone to moiture issues.

[lemoyne]

777 and all APP powders are hygroscopic, this is a known fact. The APP powders are worse than 777 but all powders that are hygroscopic become erratic when they absorb a little moisture out of the air. Most will still fire but usually the first thing to go is accuracy.
I have some Pyrodex that is 20 years old and it fires just fine but I think it chemically aged some as the groups are an inch to two inches bigger.
According to the manufactures Blackhorn is the one supposed to have a long shelf life.
I know water does not affect it much as I ran some experiments wetting it and drying it and it worked just fine.

[HEAD0001]

I quit shooting T-7 because of its Hygroscopic properties. I had a couple different cans of of loose T-7 clump up. And I have been storing powders for close to forty years. It is the only powder I have ever had a problem with. No more of it for me. Back to black. Tom.

I try to keep my reloading room at 40% humidity. Kinda tough in deep summer. During the winter, goes down to 20% with my dehumidifier running.

Thanks for the replies.