As I said I can think of lots of reasons to dump the powder back in the can, takes about 4 minutes, all of you have added some reasons I hadn’t considered.
I have not yet read what I would consider a good reason to leave it filled.

My progressive is set-up for 10mm, I had planned to load another 400rds, however I need to do a final range check, and three weeks have passed without me getting there. It may come to pass with the holidays that it will be another three weeks. Too long for powder to stay in the hopper in my view.

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