By Duane Thomas
As you get into reloading, occasionally you’ll hear people refer to “carbide sizing dies.” What the heck does that mean? I’ll give you the technically correct definition, then the practical definition. The technical definition is that carbide is “a compound composed of carbon and a less electronegative element.” For all practical purposes, what that means is we wind up with the sizing function of our reloading machine being accomplished by a material considerably harder and slicker than steel.
It’s important to recognize, when we speak of a “carbide sizing die,” that doesn’t mean the entire die is made of carbide, at least if we’re talking a pistol die set. Carbide is considerably more expensive that steel. Therefore, for reasons of cost, pistol sizing dies are not made totally of carbide, because they don’t need to be. Instead, there’s a ring of carbide inset into the die toward its entrance. If you ever see a carbide ring out of a pistol resizing die, it kind of looks like a miniature metal hula hoop, or maybe a really thin wedding ring. Carbide rifle dies, by contrast, because of the shape and length of most rifle casings, have carbide inserts that are as long as the rifle case.
Carbide sizing dies confer many advantages, one of which is longevity of the die. There are a lot of variables affecting die life, but a generally accepted rule of thumb is that a carbide sizing die will last approximately three times as long as one made entirely of steel.
There are other advantages that accrue from the carbide approach. In order to understand what they are, first let’s discuss exactly what a sizing die does:
When you fire a cartridge in a firearm, the casing expands to the limits of the steel chamber then, because of the ductility (springiness and “memory”) of brass, shrinks back down a bit so the casing may be easily extracted from the chamber, but still remains larger than it was in an unfired state. In order to reload the casing, it must be sized down again. The very first die on your reloading machine is always the sizing die, a hollow tube that, when a cartridge is run up into it, “squishes” the casing back down.
Originally sizing dies were made from solid pieces of steel. The problem with that approach, it absolutely required lubricating casings before resizing, otherwise casings would sometimes hang up in the “sticky” steel sizing die, the rim would rip out from the shell plate, and you’d wind up with a casing stuck in the sizing die. You’d then have pound the casing out, with a rod and hammer from the top of the machine through the die. Note your sizing die is open on top, for just that reason.
This potential problem was made more likely by the people who never lubricated, or even cleaned, their casings before reloading. Even with case lube and clean cases, all-steel resizing dies required a lot of energy on the handle stroke, to force the casing up into the die, and force it out afterward, which is hard on your joints over time.
Carbide sizing dies make reloading innately more pleasant. That’s why they’ve been around for so long that most people have literally never reloaded a single round of ammo with a non-carbide sizing die. And this is a good thing.
