Abstract: An adjustable case sizing die includes a die body having a threaded outer surface and a threaded inner surface. The threaded outer surface of the die body has a first pitch. The threaded inner surface of the die body has a second pitch smaller than the first pitch. A sizing insert is positionable within an interior cavity of the die body. An adjusting spindle is connected to a top of the sizing insert. The adjusting spindle has a threaded outer surface. The threaded outer surface of the adjusting spindle has the same pitch as the inner surface of the die body. The adjusting spindle is threadably insertable into the die body. Turning the adjusting spindle within the die body changes a height of the sizing insert within the die body.