Never Trim Again! RCBS X-Die

The RCBS X-Die essentially eliminates the need to trim your brass after an initial trimming. How does it work? Watch and read on to find out!

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About the RCBS X-Die

Brass preparation is one of the most tedious and time-consuming parts of reloading rifle ammunition.

This small-base die largely takes trimming out of the equation.

From RCBS:

Trim a bottleneck case once—and never trim again with the X Die Full Length Die Set, which includes an X Die Sizer and Standard Seater Die. The sizer features a specially designed mandrel with an expander ball and decapping pin attached. The patented design eliminates the need for repeated trimming after an initial trim of .020 inch off the maximum length to standardize the case.

The X Die doesn’t shorten the length of the case: The mandrel reduces the growth caused by the case mouth contacting the mandrel during sizing. Because of an extremely close tolerance between the mandrel and die neck wall, the neck wall of the case does not thicken as the case length is pushed back. Cases repeatedly sized in the X-Die will initially grow a few thousandths of an inch, and then stabilize below the maximum case length with no discernable loss of accuracy or case life. Note: Reloaders who already own a regular set of dies for the chosen caliber need only order the X Die Full Length Sizer.

- Trim a bottleneck case once—and never trim again with the X Die Full Length Die Set
- Includes X Die Sizer and Standard Seater Die
- Made in USA

Installation and Testing

This die looks just like a traditional sizing die with a mandrel and expander ball, but has a hard shoulder that prevents the case from elongating in the die.

I screwed the rod into the die body until I had between ⅛” and 1/16” of the rod protruding out the other side, and set it up on my RCBS Rock Chucker Supreme press.

With the ram raised, I lowered the die until it contacted the shellholder. I turned it approximately ¼ turn until I felt it cam over.

I lubed a Lapua .223 case that I tested my desired load with and placed it in the shellholder. With the ram all the way to the top, I screwed the mandrel down until I felt hard resistance and secured the lock ring to preserve the setting.

I trimmed this first piece of brass 0.020” ( to 1.740”) under maximum (1.760”), then chamfered and deburred it.

I primed the brass on the Rock Chucker supreme and charged it with 24.4 grains of Varget dispensed from the RCBS Chargemaster Link.

Next, I seated a Hornady 75 Gr. BT .224 A-Max bullet over top the charge on a separate RCBS Partner Press with the appropriate X-die .

After the first trimming, I fired the loaded round through my .223 trainer and reloaded it again, but with no trimming this time.

I did turn the mandrel down another half turn until I saw the case overall length go down just a little bit to 1.7425”.

Watch for bulging between the shoulder and the body! This will cause your round not to chamber.

I ran two batches of tests: 8 rounds and then 20 rounds!

We never noticed a bulge but realized we needed more mandrel crankdown and had to rerun the test with a new piece of brass.

RCBS noted in their research that they could get approximately 20 firings before the brass required trimming again. I observed the same, ensuring I was at least 0.015” under maximum after the first trim.

It didn’t grow another 0.001” until the eighth firing.

Some may postulate that the X-die stresses the brass, but 20 firings without trimming shows it is not.

Conclusion

It’s critical to fire-form the brass to your chamber and trim it the first time, but the RCBS X-die eliminates the need to trim again for approximately 20 firings. According to RCBS, brass will likely fail before needing to be trimmed again. I learned that set-up is important in this process and you may have to experiment to get it exactly how you want it.