RCBS X Die Small Base Sizer Die Only .308 Win

The RCBS X Die Small Base Sizer Die for .308 Win is a specialized rifle die designed to reduce the need for repeated case trimming—a real time-saver for serious reloaders who process large volumes or reload the same brass multiple times. Unlike standard sizing dies, the X Die uses a patented mandrel design with an integrated expander ball and decapping pin that minimizes case-mouth growth during the sizing stroke. This clever engineering means you trim your cases once to .020 inch under maximum length, then let the die do the work of controlling further growth rather than chasing length creep with the trimmer every session.

Here's how it works: as you resize .308 Win cases in the X Die, the mandrel's close tolerance with the die neck prevents the neck wall from thickening and the case from elongating excessively. Cases will initially grow a few thousandths but then stabilize well below maximum length and stay there. The result is brass that lasts longer and performs more consistently without the tedious trimming ritual. This is the sizer die only—if you're new to reloading .308 Win, RCBS also offers the X Die Small Base Set, which bundles the sizer with a standard seating die.

Small base dies are the right choice if you're working with ammo for semi-auto rifles like the AR-10 or other .308 platforms where tighter neck tension and case control matter. Reloaders who shoot a lot, process once-fired military brass, or simply want to minimize maintenance on their die set will appreciate the X Die's design.

Key Features

• Patented mandrel design reduces case-mouth growth during sizing
• Integrated expander ball and decapping pin in one die
• Minimizes the need for repeated case trimming after initial setup
• Small base configuration for semi-auto .308 rifles
• Cases stabilize below maximum length without discernible accuracy loss
• Extends case life and improves consistency across reloading sessions

Specifications

Frequently Asked Questions

Is this die compatible with all .308 Winchester rifles?

The X Die uses a small base design, which is optimized for semi-automatic .308 rifles like the AR-10 and similar platforms where tight case control is beneficial. If you're reloading for a bolt-action .308, a standard die may work, but the small base sizing is designed with semi-auto feeding in mind.

Do I still need a separate decapping tool with this die?

No. The X Die includes an integrated decapping pin, so you can deprime and resize in one stroke without needing a separate decapping die or tool.

What comes in the box?

This is the sizer die only. You receive the RCBS X Die Small Base Sizer for .308 Win with its integrated expander ball and decapping pin. If you also need a seating die, you can purchase the X Die Small Base Set or order a seating die separately.

How much do I need to trim cases before using the X Die?

Trim your .308 Win cases to .020 inch under the maximum case length once before you start using the X Die. After that initial trim, the die's mandrel design controls further growth, so you won't need to trim repeatedly like you would with a standard sizer die.