I had to pull bullets from about 30 rounds because I found out that they had too much bullet runout (I just got a concentricity gauge). When I went to dump the powder on a lot, but not all, of them, the powder would not easily pour out. I had to tap the case on the side of the powder bottle to get it all out. They were loaded in September and have not been in a humid room since then. They also were not compressed loads.
Why would the powder stick together and not dump out easily???