The benefits of loading a cartridge long is that you may tailor the cartridge dimension to more closely fit a specific firearms’ dimenstions. This is a technique often used by many competitive shooters and accuracy enthusiasts to improve accuracy as part of the tuning process. https://bergerbullets.com/effects-of-cartridge-over-all-length-coal-and-cartridge-base-to-ogive-cbto-part-1/