Types of Rifle Dies and How They Work


There are two basic types of rifle dies that are needed to complete the reloading process:

  • The first is the resizing/depriming die
  • The second is the bullet seating/crimping die.

Both are used in conjunction with each other to make sure your brass casings are shaped and sized correctly. Let’s discuss each of them and the basics of how they work.


Brass must be resized because when a cartridge is fired, the case expands to fit the chamber.

The case must be resized to factory specs when reloading to ensure reliable functioning. All rifle dies are made of steel.

This means that to resize the brass, case lube is required. Case lube will prevent the case from becoming stuck in the die.

Sizing dies come in two main styles: full-length and neck. Both styles of dies will remove the spent primer from the case, while resizing the brass.


The full-length die does exactly what it says, it resizes the brass back to factory specs from the neck all the way down to the base of the case.

This die should be used when loading for semi-auto, lever-action and pump-action rifles, or when loading the same caliber for multiple guns.

Full-length resizing ensures that the reloaded ammunition will function properly in these types of firearms. Full-length sizing can be used for any type of action.

full length die
This is a full-length die for the .223 Remington.


A small-base die is a specific type of full-length die that is used when reloading for semi-auto rifles like the AR-15 or AR-10.

The small-base die functions the same as a full-length die, but it compresses the brass casing a bit more (about .001”).

It may also push the case shoulder back slightly. This provides more room for the case to extract for improved reliability in semi-auto firearms.

Unfortunately, it also shortens the case life due to the extra stress.

rifle dies
You can see the difference between the full-length die (left) and the small-base die (right).


Neck-sizing dies only resize the neck of the brass and should primarily be used when loading for one rifle, usually a bolt-action.

The belief is that sizing only the neck back to factory specs will enhance the accuracy of the cartridge because it will fit the chamber of a particular rifle better and allow less case expansion during firing.

It is also believed that by not working the brass in a full-length die every time, case life will be extended.

Neck sizing is not recommended for semi-auto, lever-action and pump-action rifles due to reliability issues.

Neck sizing is also not recommended for multiple firearms in the same caliber unless brass is kept separate for each rifle, because chambers vary in dimensions.

neck-sizing die
Neck-sizing .308 Winchester die.


The seating/crimping die pushes the new bullet into the case and is adjustable for depth.

There are several variations of seating dies, but all perform the same function. The seating die can also be adjusted to crimp the cartridge around the bullet.

This is sometimes desired in semi-auto actions and tube-fed firearms so the bullet will not move in the case during recoil.

Most manufacturers will offer variations of these dies. For example, match-grade dies will hold the ammunition to tighter tolerances for better accuracy.

Other variations are collet dies that squeeze the neck down to specs and body dies that resize the body of the case only.

These resizing and seating dies are most commonly purchased as sets, but can also be purchased individually.

crimp die
This is a crimp die for the .300 WSM.

Conclusion: Rifle Dies

Once you have determined the number and type of firearms you will be loading ammunition for, you can decide on what type of rifle dies you will need.

If you don’t know, or think you might expand your operation, you may want to purchase a kit with a variety of rifle dies so you have all your bases covered.

Either way, it is important to select the correct dies and to use them for a safe and successful loading experience.

What type of rifle dies do you use for reloading or handloading? Let us know in the comments below!

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