As a former Lee equipment user, your powder disk is not returning completely to the fill position, you don't have the powder measure at least 50% full, and you may have significant variation in case length. My suggestion is that you check your powder measure for smooth operation and full cycling of the disk front to rear. My experience with Lee disk powder measures was that they functioned, had to be kept spotlessly clean, and there was no correlation between the list powder charge and the actual powder charge.

Military brass has the thickest walls and R-P have the thinnest. I have had 38 spl loads that the bullet would turn easily, but were accurate without any squibs.

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S&WHF 366