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.
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 calibers, carbide sizing dies allow you to quickly resize without applying any lube to the case. But rifle cases always need lube.
Neck-Sizing Dies
Neck-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
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.
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
Similar Posts:
- DIE BASICS: Full-Length Dies, Neck-Sizing Dies, Small Base Dies
- SIZING DIES: Full-Length Dies, Neck-Sizing Dies, Small Base Dies
- Basics of Case Sizing — How To Set Up and Use Sizing Dies
- How to Set Up Full-Length Sizing Dies and Control Shoulder Bump
- Full-Length Sizing Die Set-Up — Tip from Sinclair International
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Tags: Brownells, Bump Gauge, Bushing Die, FL Die, Neck sizer, Neck Sizing, Necking, Redding, Shoulder Bump, Sinclair, Sinclair Int'l, Small Base Die, Type S
Always a lot of talk about overworking the case neck with anything but a bushing die. I find the primmer pockets go well before the neck. Never had any overwork problems with standard FLS dies.
“Neck-sizing dies resize only the neck of the case. The benefit of sizing only the neck is that the brass is “worked” very little, …. ”
Disagree. When neck-sizing, the body of the case continually expands until the case can no long be chambered. At that point the entire case must be resized to ensure seating once again. To bring the case back into its original dimension now requires “over working” the brass because it has moved its farthest from the original design. “Overworking is a function of distance” not frequency. Full Length sizing each and every time ensures the brass is worked very little [moved a short distance] and restores the original dimension. There will never be a problem chambering it. Shooting a morphing [continually expanding] case body is never conducive to consistency or accuracy.
Ask members of the NBRSA Hall-of-Fame how many shot themselves into the Hall by neck-sizing.
When going to the “bump gauge” link I noted some odd info for the 40 degree shoulder gauges. I inquired and Sinclair/Brownells responded, “…disregard the cartridge ID of 280 Remington. 749-011-482 is for AI up to 6mm with 40° shoulder, and 749-011-483 is for 6mm up to 338 AI with 40°.”
Full length and body dies DO NOT return the cartridge case to its ‘original dimensions due to “spring back”. The cartridge case will always try to spring back to what it was fired too. The full length and body dies size the cartridge case so that when the cartridge case does try to spring back to what it was fired to in your chamber that it is still undersize slightly (depends on the internal dimension of THAT DIE) to chamber easily in most cases. There are times however where the die may have internal dimensions that are to the large side of SAMMI specs and the chamber of the rifle is to the small side of SAMMI specs where the cartridge case is NOT SIZED ENOUGH so that when it springs back as it comes out of the die that it now MAY not chamber ( when it did before sizing) or chambers hard.Using once fired range brass can be the main culprit here also. What happens is that the case body is sized but the shoulder area of the cartridge case is either not touched or not touched enough to move the shoulder back or move the shoulder back enough so that when the cartridge case springs back it is till oversize in head space for the rifles chamber. In this situation you can have material removed from the bottom of the die to shorten it or contact the manufacturer, send them the die and some fired cartridge samples and have them hone a new die for you if they offer that service. Small base dies MAY not solve this issue either as they are made to a smaller case body sizing dimension but do not always have a smaller shoulder sizing dimension.
Phil Hoham
Berger Bullet tech
outstanding , helped a lot