12 Gauge Shotshell Resizing Die

12 Gauge Shotshell Resizing Die

About a month ago I teased some of the new tools I started working on late last year, including a die and accessories for reloading 12 gauge shotshells on a conventional metallic cartridge press.

In scenarios where you’re using your own powder measure, trickler, specialty components and roll crimper to produce precision slugs or buckshot, a conventional press represents a significant investment in equipment you may not even use.  Likewise, when working with high-brass hulls, the kickout system used in many shotshell presses can be miserable at the best of times.

For that reason, I’ve designed a complete set of tools to allow folks specifically focused on producing buckshot and slugs to do so without requiring a dedicated shotshell press.

In this article I’ll start off by demonstrating the resizing die, which is also the main platform to which other accessories can be attached for completing other shotshell reloading processes.


As you’ll see in the video above, this tool is comprised of three components including a die, base, and carbide ring.

Beginning with the die, I selected a semi-stainless steel to produce a corrosion resistant body that’s still strong enough to handle the forces generated by resizing as well as the other processes it will be used for.  The die employs two different thread standards, one to fit the press, and another to mate up properly with the carbide sizing ring.

Moving on to the base, this is a tool steel hull holder similar to those used in metallic cartridge reloading.  It’s designed to fit most 12 gauge hulls, and will slot into any Lee Precision or compatible press ram.  It’s worth noting, some Challenger brand hulls which do not conform to SAAMI specifications will not fit the hull holder due to their non-standard brass rim height.

Finally we have the sizing ring.  Made from carbide steel, this is actually a standard MEC 600 part. The decision to employ these in my design was simple; they’re tough, built to exacting specifications, and at a price I could never hope to match.  While I did explore some other options, in my opinion nothing short of carbide is acceptable in a modern reloading die, and MEC’s sizing ring represents the best and most affordable way to achieve that.

With the components covered, let’s take a look at setup.


The first thing you need to know is that this tool will not fit a conventional 7/8-14 press.  Due to the diameter of 12 gauge shotshells, there simply wouldn’t be enough material left in the die to handle force of the resizing operation.  For that reason I’ve designed it using the older 1 1/4-12 standard. In layman’s terms; you need one of the larger style presses that can handle 1 1/4-12 dies.  Currently I use a Lee Precision Classic Cast press, which I can guarantee  will accept this kit perfectly.  Virtually every other manufacturer produces a 1 1/4-12 press (usually their strongest models), however I do not own any of them and cannot speak to their suitability.

Shown in the video above is my Lee Precision Classic Cast press.  To install the sizing kit, the user begins by removing the 7/8-14 adapter it ships with.

With that done, the operator threads the MEC carbide ring onto the sizing die, then installs the whole affair into the press. Die position isn’t super-important as ultimately the base will bottom out on the die regardless.

Finally the user slots the base into the ram of the press, with the open end facing one side for easy access, and we’re pretty much done.


So simple even a YouTube content reviewer couldn’t screw it up, sizing hulls consists of sliding them into the base, raising the ram until it bottoms out on the die, and then dropping it back down again to extract.

I was originally a little worried that the size and surface area of the brass head might make it challenging to work with, but this is probably the easiest sizing operation I’ve performed.  The power and leverage provided by the metallic cartridge press is such that this operation requires almost almost no force at all.

The resizing die works equally well with both low and high brass hulls.  This was critical to me during the design phase as I find high-brass hulls miserable to size on conventional shotshell presses that use a sizing ring.


After testing a Winchester Super X high brass hull, I began with a diameter of 0.809″, right on the edge of max diameter according to SAAMI.  After processing it with the resizing die, that dropped to 0.801″; well within acceptable tolerance.

Moving on to a low brass steel head Federal hull I began with a diameter of 0.811″ (far too large).  After processing it, it measured in at exactly 0.801″ again.

As with metallic cartridge casing sizing, the lip on the hull holder means brass doesn’t size all the way down to the rim, but also like metallic cartridge casings, it doesn’t matter.  Both hulls chamber and cycle perfectly, as they would if they’d been sized on a MEC or any other carbide ring-based press.


So that’s the new 12 gauge hull resizing die.  In the coming weeks I’ll be demonstrating a number of other accessories designed to work with this tool, which will allow you to load completed buckshot and slugs without any need for a dedicated shotshell press.  In the mean time, if you’re interested in this or any of my other tools, by all means check out my project site and online shop at www.tatvcanada.com

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