Step-By-Step Reloading Part 7: More On Sizing Dies | Top Rated Supplier of Firearm Reloading Equipment, Supplies, and Tools - Colt

Step-By-Step Reloading Part 7: More On Sizing Dies

Step-By-Step Reloading Part 7: More On Sizing Dies
Last month, we looked at the basic types of sizing dies, and how they offer different benefits for different types of reloading. This month, we look even closer at sizing dies, especially those with internal components you can exchange or modify to help accomplish specific reloading tasks.

Decapping Pins & Assemblies

Most sizing dies include a decapping pin or assembly that pops out the spent primer as the case is inserted into the die. The decapping assembly is made of hardened steel, or some other super-hard metal that stands up to repeated use. It usually holds an expander button and a replaceable decapping pin, which is what actually makes contact with the spent primer and pushes it out.

Decapping pins are held in by a number of different methods, depending on the die manufacturer. Most are held by a small collet or retainer that threads to the end of the assembly. Even though decapping pins are sturdy and well-made, it is possible for a pin to bend or even break if the die is not properly adjusted. You can also lose a pin when you’re cleaning your dies or have them otherwise disassembled. It’s always a good idea to have replacement pins on hand.

Proper Decapping Assembly Adjustment

A good rule of thumb for setting up the decapping assembly is what we call the "Ten-Cent-Rule." Adjust your decapping pin to protrude from the bottom of the die approximately the thickness of two nickels.

Sizing die cutaway. Decap pin protrudes approximately two nickels from the base of the die. Also, the expander ball is positioned below the case neck (case neck area is at the top of the die threads)
This should get most dies started and avoid decapping assembly damage. If you ever experience a recurring problem of bending or breaking decapping assemblies, keep in mind that you want to avoid having the expander button in the neck of the cartridge when the depriming process is occurring. Remove your decapping assembly, stand a cartridge on your bench top, and stand your decapping assembly next to it. Is your expander below the case neck? If not, be sure to lower it accordingly.

Expander Buttons

Inside most sizing dies there is an expander button attached to the decapping assembly. It is a specially-shaped part that helps keep the inside case diameter consistent from case to case as you run them through the sizing die.  Your reloading die’s internal dimensions are such that the case neck is oversized when the brass is run into the die. When you pull the brass out of the die, the expander button travels through the oversized case neck and expands it to create equal neck tension for bullet seating, regardless of inconsistencies in the neck wall thickness. As simple as this sounds, there are several things to consider about expander buttons.

A typical decapping assembly with the pin removed
Some reloaders like to take the expander buttons out of their dies and polish them with a crocus cloth or some similar material. The reason they do this is that making the button smooth and shiny reduces friction. Reduced friction means the button still expands the case mouth, but doesn't catch on it and thus won't pull on the brass. In turn, this minimizes the case neck stretch and means you won't need to trim cases as often - which frees up more time for important things like shooting! Essentially, a slick, shiny expander button helps extend case life by reducing how much the brass is worked by the die.

Another way to reduce friction with the expander button is to replace the original decapping assembly with one that has a carbide expander button. The carbide is very hard and very slick, which is why it's used so often in pistol die sets that don't require any lubrication. This Sinclair video shows you in more detail exactly how the carbide expander button sets work inside your die.

Tapered buttons are another way to modify your decapping assembly, and they serve a very specific purpose: they let you change the caliber of the case to "neck up" to a different bullet size. Reloaders who like to make their own "wildcat" cartridges find tapered buttons very useful. You can neck up a .17 caliber cartridge case to accept .22 caliber bullets, for example. This is very useful when the cartridge you've selected is not readily available from major manufacturers. Benchrest shooters confront this situation with the 6mm PPC cartridge – thecartridge for 100 to 300 yard benchrest shooting. The 6mm PPC case is easily formed by necking up 220 Russian brass to 6mm.

Lastly, don't forget to use a good dry lubricant on the expander button. Besides polishing, this is the best way to reduce wear and friction that leads to case stretching. Redding's Imperial Application Media is a fine graphite powder mixed with high-density ceramic spheres. You simply dip the case neck straight into the media to apply a thin, dry film that won't contaminate the reloading process. It's fast and easy.

Die Lock Rings

Die lock rings help keep your reloading dies tightened securely into your press to make sure nothing changes as you repeatedly run cases through it. Many die lock rings have a screw that locks the ring into place by threading directly into the die itself with a leaded thread insert protection.

Example of standard rings with locking screw that tightens against die threads
Fastening your die lock rings enables you to reinstall the die almost exactly like it was the last time you used it, though it's still a good idea to use a headspace gauge to confirm the exact amount of sizing. Cross-bolt lock rings have a split-ring design so that the ring actually tightens around the die instead of into the threads, which prevents damage to the threads. Sinclair cross-bolt lock rings are great, as are the Forster rings, and both fit on any 7/8"-14 threaded dies

Cross bolt lock rings
Sinclair Die Lock Ring Pliers are handy tools to have on your reloading bench too. They help make it easy to install and remove the dies. Sizing dies are like so many other things in precision reloading. The operations they perform sound very simple, but there are so many ways to modify, control, and improve the results they produce. Now that we’re done with sizing dies, next month we'll talk about seating primers into the cases.

Roy Hill
Brownells/Sinclair Copywriter