Full-Length Sizing Die Set-Up — Tip from Sinclair International

How to Set Up Your Full Length Sizing Die
by Ron Dague, Sinclair International Technician
From Sinclair’s Reloading Press Blog

At Sinclair International, we are often asked for a fool-proof method to set up a full-length sizing die, and begin reloading our fired cases. The method used by many target shooters today is to set up your full length die to closely match your rifle chamber and minimally full-length size your cases –as little as .001″ for bolt-action rifles. I prefer to use this method for all of my bolt-action cartridges.

STEP ONE
I like to de-prime five (5) cases (de-prime only, do not full length resize) and measure from the base of the case to the shoulder with our Sinclair Comparator Body (09-1000) and Bump Gage Insert(09-10200). We refer to this as our headspace measurement. Our Electronic Caliper (#MIC-14) works well and may be pre-set at .000” making this headspace measurement easy to capture. The Sinclair Comparator/Gauge Body and Bump Gage Inserts make this task fairly simple. L.E. Wilson Tools & Gages, Hornady Manufacturing, and RCBS all make similar units to achieve your headspace measurement.

STEP TWO
With your full-length die threaded into your reloading press, loosen the lock ring and run the press ram up toward the full length die with a shell holder in place (with no case). Then, screw the die toward the shell holder until it stops. Back the die out of the press and away from the shell holder one full turn and set the lock ring finger tight.

STEP THREE
Lubricate each of the cases with your favorite sizing lube (my favorite is Imperial Sizing Die Wax) and resize a case. Again, take a headspace measurement from base to shoulder. [When running the case up into the die, be sure the press ram moves the full limit of its upward travel.] If there’s no change in the measurement from the fired dimension, loosen the die lock ring and turn the full length sizing die downward 1/8 of a turn. [Editor’s Note: You’ll need to use smaller turn amounts as you get close to the desired amount of bump. We suggest moving just a few degrees of die rotation at a time once you’ve reached the point where the die hits the shoulder without moving it back.] Now repeat the sizing process with a second lubricated case and take the measurement again. Keep rotating the die downward gradually (in small increments) and repeat the case sizing process until you see approx-imately .001”-.002” reduction to your fired headspace measurement. We prefer a headspace reduction of approximately .001″ – .002″ for bolt action rifles and .003″ – .005″ for semi-auto rifles. You can adjust to your rifle as to what works best. Don’t forget to load 10 rounds or so and try them from the rifle’s magazine to make sure they function properly.

Full-length Sizing vs. Neck-Sizing
Just a quick word on neck sizing…..I have personally never been a big fan of neck sizing. Often times when I put neck sized cases back in the rifle, the bolt would close with some drag, or it would be a bit “snug”. This was mostly recognized with factory rifles. I didn’t have any problems with accuracy, just with cycling the action for a follow up shot. If your rifle is custom chambered with the action straightened and trued, neck sizing will work well on 4-5 firing’s and then you will need to full length size or use a body die to set the shoulders back when the cases begin to “stick”. Hope these tips help make the use of a headspace gauge and full length die set up much easier.

Ron Dague
Sinclair Tech and Reloading Instructor
800-717-8211
rond@sinclairintl.com