The micrometer adjustable ram is used within a frame having die mount and lever. A die is releasably secured within the die mount and a firearm cartridge is releasably secured to the end of the ram for resizing or bullet reseating. In operation, the ram extends into an extended position and the cartridge held at the end of the ram is inserted into the die held within the die mount. To adjust the length of the cartridge that is inserted into the die and thereby the amount of resizing and seating done to the cartridge, a micrometer assembly is provided within the ram that can be adjusted by the reloader. Furthermore, the micrometer assembly can be locked prior to use to assure that the ram, and cartridge held thereon, are coaxially aligned with the center axis of the die for more precise and repeatable resizing and reloading.