December 5th, 2018

DIE BASICS: Full-Length Dies, Neck-Sizing Dies, Small Base Dies

Sizing dies brass sinclair redding full length neck neck-sizing small base

This article is part of Sinclair Int’l Step-By-Step Reloading Series. Most of the products mentioned in this article are sold through Brownells.com.

by Roy Hill, Brownells/Sinclair Copywriter
Making your own precision handloads is a meticulous journey with many steps, many important matters to consider, and many sets of measurements to calculate. For those who pursue the perfect group, the highest score, the really long accurate shot, the rewards more than outweigh the effort. Choosing the right cases, deburring the flash holes, making the primer pockets uniform, trimming the cases, and lubricating them are all familiar – and critical – steps along the journey. And now that your brass preparation is complete, you are at last ready to start running the cases through your press and fill them with primers, powder, and bullets. The very first die the brass encounters is the sizing die. You insert the case, work the press’s lever to return the case to its correct pre-fired dimensions – and the journey continues.

Sinclair International Int'l fL full-length sizing die bump die shoulder bump gauge

There are three types of sizing dies to think about: neck, full-length, and small base. All three have specific benefits and potential drawbacks, and you should choose the type of die you use by thinking very carefully about what kind of shooting you plan to do with your handloads. No matter which type you select, most sizing dies will also punch out the old spent primer with some sort of decapper assembly that uses a hardened steel rod. Many types of sizing dies use an expander ball inside the die to make sure the neck of the case will accommodate a bullet after being sized. With some size dies, the expanders are easily removable and interchangeable, letting you get exactly the neck tension you want. If you are reloading for pistol cartridges, carbide sizing dies allow you to quickly resize without applying any lube to the case. But rifle cases always need lube.

Neck-Sizing Dies
Sinclair International Int'l fL full-length neck size neck-sizing die bump die shoulder bump gaugeNeck-sizing dies resize only the neck of the case. The benefit of sizing only the neck is that the brass is “worked” very little, letting you reuse the same cases many times over. Also, cases that have already been fired in your rifle are perfectly fireformed to fit that rifle’s chamber, which can help accuracy. However, neck-sized cases will fit only the specific rifle they were originally fired in, and may still require a little extra force to chamber or extract.

Sinclair recommends that neck-sized-only cartridges should not be used any in other rifle besides the one they were originally fired from [unless they are also FL-sized], or in any action other than a bolt-action. Neck-sized-only rounds are great for the target range or the benchrest but should not be used in critical situations like military or police operations, or hunting. And if you fire them enough times, neck-sized cases will still need to be full-length sized periodically for you to keep using them.

Full-Length Sizing Dies
Full-length sizing dies do exactly what their name says: resize the full length of the case, not just the neck. Full-length sizing helps create handloads that will function in any rifle, not just the one from which the cases were originally fired. The potential downside of full-length sizing is that it may shorten case life because it works the brass more than neck sizing. But it’s possible to “tune” today’s full-length sizing dies so they barely work the brass at all, as this article by Sinclair Reloading Tech Ron Dague shows.

Illustration Shows How a Full-Length Sizing Die Works
Sinclair International Int'l fL full-length sizing die bump die shoulder bump gauge

Another way to reap the benefits of full-length sizing is to use Redding’s full-length bushing dies, which size the full length of the case but use a system of interchangeable bushings that enable you give the case neck the bare minimum of resizing needed. To see how finely adjustable bushing dies are, and how they resize the case while fully supported, CLICK HERE for Video. The neck bushing helps you precisely control the neck tension to help increase the consistency and accuracy of your handloads.

Redding Custom full length dies

Small Base Dies
A Small Base Die is just another type of full-length sizing die, but one that is typically used when reloading for semi-automatic rifles, like the AR-15, M14, or AR-style .308 rifles. (It may also work well for bolt guns that need extra sizing on the lower section of the case.) A small base die works exactly like a full-length sizing die, only it compresses the brass just a bit more, usually about .001″ more, and may even push the case shoulder back just a hair. Small base dies give that extra bit of compression to the brass to help make sure the case will properly extract from a semi-automatic firearm. The upside is that you get precision handloads that should work flawlessly in your semi-automatic. The downside is case life is really shortened, especially compared to brass used only in one bolt-action rifle, because the brass is worked more.

Shoulder Bump Gauges
A handy tool for setting up your full-length sizing dies as close as possible to your rifle’s chamber is the Sinclair bump gauge. The bump gauge lets you resize the case as little as possible, to extend case life and help your handloads fit your rifle almost like a neck-sized only die. You use deprimed cases fired in your rifle and bump gauge inserts to help you set up the die so it resizes the case only about .001″ to .004″, depending on what type of rifle you’re shooting.

Video shows how to use a shoulder bump gauge to set up your full-length dies

Sinclair International Int'l sizing die bump die shoulder bump gauge

Article Find by EdLongrange. We welcome reader submissions
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February 4th, 2018

Full-Length Sizing Die Fit — Diagnosing Stiff Bolt Lift Problems

Resizing Die Alex Wheeler Shoulder Bump Die fitting Full-Length

In this video, gunsmith Alex Wheeler explains how to ensure that your full-length sizing dies fit your brass properly. With many cartridge types, it’s not unusual for factory dies to be slightly large in the bottom section. When the diameter of a FL-sizing die is too large near the base, this can leave the bottom section of fired cases “unsized”, with the result that you can have extraction issues and stiff bolt lift, or what Alex calls “clickers”. At the same time, it’s not unusual for dies to over-size fired cases at the shoulder (i.e. reduce the shoulder diameter by .004″ or more).

We strongly recommend that all hand-loaders watch this video, particularly if you load cases 6+ times with relatively high-pressure loads.

Alex explains that a key dimension is the diameter of a fired case 0.200″ above the case head. If your die does not size your fired cases at this point, you should get a FL die that does. This could be a custom die ground to fit your chamber, or it could be a “small-base” die specifically designed to “hit” the bottom section of the case. Alex also notes that some FL dies have an inside chamfer at the mouth of the die, right at the very bottom. (See video at 3:55). This can leave the section of the case right above the extractor groove unsized, which can also lead to “clickers” and stiff bolt lift.

Paint Your Brass to Find Problem Areas
If you are having stiff bolt lift or extraction issues, Alex explains that you can “paint” your brass with magic marker (or dye-chem), and then place the case in your chamber. On the “hot spots” where the case contacts the chamber wall, the marking will rub off, allowing the brass metal to shine through in the problem area(s). This will illustrate where you need better sizing from your die.

“You can ink up the case with some magic marker or dye-chem. If you are getting clickers, go ahead and mark up the case and chamber it and see where it’s wearing. This will help you diagnose [whether the problem] is coming from the base, is it coming maybe from a score in the chamber… it can even happen at the shoulder although that’s pretty rare. Usually the dies size enough at that point.”

Did you find this video helpful? View more informative Tech Tip Videos on WheelerAccuracy.com.

Video Tip from Boyd Allen. We welcome reader submissions.
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March 23rd, 2017

PMA Micro-Die Adjuster — Try One And You’ll Be Spoiled

PMA Tool Micro Die Adjuster .001 Shoulder Bump full length sizing lift shim

Wouldn’t it be great if you could quickly and easily adjust shoulder bump during the full-length sizing process, without struggling to move die lock-rings by trial and error (or fiddle with shims). Well you can. The PMA Micro Die Adjuster is a brilliant little device that replaces the lock ring on your FL sizing die. It allows you to move the die up and down in precise, tiny increments. The tool has .001″ index marks, but you can easily set your die between the marks to achieve .0005″ (half-thousandth) adjustments.

The affordable PMA Micro Die Adjuster is offered in two versions, an upgraded model with a handy thumb screw for $69.95 (photo above), as well as the original with set screw for $65.95 (photo below).

PMA Tool Micro Die Adjuster .001 Shoulder Bump full length sizing lift shim

To see how the PMA Micro-Die Adjuster works, watch this video by our friend Boyd Allen:

Many of our Forum members now use the PMA Micro Die Adjuster, and they give this specialty tool high praise. Here are actual reviews by Forum members and other verified tool buyers. Read more comments in this AccurateShooter Forum Thread.

PMA Micro Die Adjuster User Reviews

“No more ‘close enough’ for headspace[.] With this tool set-up it’s easy to put headspace exactly where you want it, then repeat it exactly for subsequent batches for the same cartridge.” — JohnF

“I have four of these Micro Adjuster rings and all I can say is that it works and it is repeatable. I bump my brass .0005″-.001″ and this die lock ring will do it without issue.” — TrapperT

“I size brass for four different 6.5×47 rifles (chambered with three different reamers) using a single die, set in the PMA Adjuster. I have to say… I should have bought one sooner. Adjusting it is very quick and repeatable to well under .001.” — /VH

“I’ve been using PMA’s lock ring for some time now and find it to be very easy to adjust to within .0005″ on a single piece of brass. Very quick to do as well. One thing I have found is that if you still need that half-thou adjustment I will run the brass once more at the same setting before I make that .0005″ adjustment and 50 percent of the time that does the trick. The marked increments are in .001″ scale so if you go half way in between there’s your half-thousandth.

PMA Micro-Adjuster vs. Shims

Many hand-loaders have abandoned shims after trying the PMA Micro Die Adjuster:

“Shims [require] you to completely remove the die. That gets old rather quickly after having used the PMA adjustable lock ring.” — Patch 700

“Great product. Shims used to drive me crazy, put a .002 in and get .0035 of change. With this if you want .0015 set it and that’s what you get.” — John B

“I like mine — adjustments are easy and it will adjust very fine. I used to use .001″ shims. Now can adjust my bump as fine as I want.” — Joe139

PMA Micro die adjusterProduct Description from PMA Tool
The PMA Tool Micro Die Adjuster (MDA) replaces your existing lock ring and can be used with nearly any 7/8-14 full length sizing die. We successfully used this tool with sizing dies from Redding, RCBS, Hornady, Lee, Harrells Precision and those made from Newlon Precision die blanks. It allows you to easily make adjustments to your “shoulder bump” as fine as .0005″. The engraved marks on the MDA are equal to approximately .001 inches (true adjustment .000992″) of adjustment to the shoulder bump. Splitting the engraved marks is therefore approximately equal to .0005″. The design of the MDA does not allow it to work with the Forster Co-Ax press. Some custom dies for very short cartridges may require the use of an extended shellholder. Micro Die Adjuster shown in use installed on Custom Newlon/Scott 6mm PPC Die and Harrells Precision Compact Press.

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May 5th, 2015

Intro to Full-Length Dies, Neck-Sizing Dies, and Small Base Dies

This article is part of Sinclair Int’l Step-By-Step Reloading Series. Most of the products mentioned in this article are sold through Sinclair’s webstore.

by Roy Hill, Brownells/Sinclair Copywriter
Making your own precision handloads is a meticulous journey with many steps, many important matters to consider, and many sets of measurements to calculate. For those who pursue the perfect group, the highest score, the really long accurate shot, the rewards more than outweigh the effort. Choosing the right cases, deburring the flash holes, making the primer pockets uniform, trimming the cases, and lubricating them are all familiar – and critical – steps along the journey. And now that your brass preparation is complete, you are at last ready to start running the cases through your press and fill them with primers, powder, and bullets. The very first die the brass encounters is the sizing die. You insert the case, work the press’s lever to return the case to its correct pre-fired dimensions – and the journey continues.

Sinclair International Int'l fL full-length sizing die bump die shoulder bump gauge

(more…)

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