Lee 458 Socom 3-Die Set. Includes Full Length Sizing Die Micrometer Bullet Seating Die Powder Through Expanding Die Universal Shell Holder Powder Dipper and Instructions/Load data. Select this die set if you are reloading mixed range brass. Nothing helps accuracy more than uniform start pressure that is the level of pressure to begin the bullets travel down the bore. Bullet seating depth affects this important pressure. For best accuracy seat the bullet so the Ogive is touching or nearly touching the rifling. If your firearm has a magazine that limits your seating depth and you are unable to touch the rifling with the bullet restore accuracy with the accessory Lee Factory crimp die.