While you work the press the dies do the actual work. Dies can serve a number of functions suck as primer pocket swaging, simply depriming or decapping a case to sizing, expanding the case mouth, seating the bullet, and even crimping the bullet. The key is to select the correct dies for your application and use them accordingly.
These speciality dies are listed because these are what we have experience with. There are countless speciality dies on the market and you should research any that you intended to use.
Universal Decapping die: This die functions only to deprime a case, a function often performed by sizing dies. Its useful to people to want to work the primer pocket or clean their brass and primer pocket without sizing the case. Aaron uses one of these on most cases. You often find these used in single stage presses and progressive presses that prime on the up stroke of the ram.
Primer Pocket Swaging die: This die is used to remove the crimp from primer pockets on military brass, or military style brass. Crimped primer pockets are often found on 5.56 and 7.62 NATO brass as well as most (If not all) 6.8 SPC brass. At least one Dillon press swages the primer pocket removing the need for this die. Both RCBS and Dillon manufacture primer pocket swaging machines that also eliminate the need for this die.
Powder Check die: Used almost exclusively on progressive presses this die usually warns the operator of impending doom from an under or over charged case. Some Powder Check dies actually prevent the press from continuing like the RCBS lockout die.
Bullet Feed die: Designed to be used with bullet feeding mechanisms on progressive presses these dies place a bullet into the mouth of the case. Hornady’s Bullet Feed Die comes with a Powder Through Expander to be used with their powder measure and case activated powder drop die.
Case Activated Powder Drop Die: While we are using the Hornady product name, RCBS and other manufacturers have similar products that allow their powder measures to be used on turret and progressive presses to automatically dispense powder into the case.
File Trim Die: This is a die that will allow you to use a file in order to trim a cartridge case to the correct length. These dies are often useful in forming cases into a different caliber. It is not uncommon to learn of someone using a file trim die to resize .30-06 brass for use in .270 Winchester rifles.
Sizing die: This die resizes the case completely or just the neck depending on application. Full length resizing dies resize the entire case returning it to factory specifications. A Neck sizing die resizes just the neck of the case leaving the rest of the case fire formed to the chamber. A neck sized case is matched to the rifle that it was fired in and should not be used in others. Additionally neck sizing should only be used in bolt action rifles.
Case Mouth Expanding die: Used primarily for handgun ammunition this die expands the mouth of the case so that a bullet can be seated easier. Too much or too little expansion can significantly shorten the case life and should be avoided.
Seating die: A Seating die is used to set the bullet at the desired depth. Many seating dies have some form of crimp capability, often that crimp capability produces a roll crimp. Some seating dies produce a taper crimp.
Crimping Die: A Crimping die is used to crimp the case mouth around the bullet. There are two types of crimps that can be applied. First is a roll crimp which rolls the case mouth into the bullet and is not suitable for use in most semi-auto handgun cartridges. The second is a taper crimp that tapers the mouth of the case so that it tensions round the bullet. A taper crimp is ideal for Semi-Auto handgun cartridges however it is not ideal for magnum revolver loads.