Sizing Dies

Upon firing, pressure created by rapidly expanding powder gas causes the brass case to swell out against the chamber walls. The sizing die provides a means of returning the case to dimensions that will allow the reloaded cartridge to chamber easily the next time it is used. With few exceptions, resizing does not return a case to its original, unfired dimensions. To help define the degree of sizing being accomplished, most manufacturers will designate dies as neck sizing, full-length, or small base dies. As the name implies, neck sizing dies will resize only the neck portion of the case, without touching the shoulder or body at all. For cases that will be reused in the same firearm, neck sizing may be a viable option. Since the body and shoulders are not resized, the case is custom fitted to the chamber in which it was previously fired. Problems arise, however, when the case is fired in a different rifle. Minute dimensional differences can lead to difficulty in chambering, poor accuracy and shortened case life. As a result, neck sizing should be reserved for cases that are to be used in the same rifle they were originally fired in, and in noncritical situations. When using neck sized cases, it may still be necessary to full length resize the case every fifth or sixth loading, as chambering becomes slightly more difficult with each successive firing. For this reason alone, neck sizing is best suited to bolt actions. Other action types lack the tremendous camming power necessary to chamber a tight fitting cartridge, and may eventually result in serious chambering difficulties.
The rim of this .308 Winchester case has been torn off by the shellholder, leaving the case stuck in the die. Extracting it without damaging the die will requirea stuck case removal kit.

The most common form of sizing in use today is full length resizing. Unlike a neck sizing die, full length resizing sizes the entire case, neck and body. While this does work the brass a bit more, it also allows the reloaded cartridges to be used in rifles other than the one in which the case was previously fired. Full length resizing also allows for easier chambering in action types not having the camming power of a bolt action.

Stuck Case Removers

The first steps in removing the case are to drill and tap the case head.

If full-length sizing is attempted without proper lubrication, a stuck case will be the likely result. This usually occurs when friction between the case and the die causes the case to seize in the die. Attempting to forcibly lower the ram will cause the shell holder to tear through the rim on the ram’s downstroke. When this happens, a stuck case remover is required to extract the case. Most consist of a drill bit, a tap, a base unit, a cap screw and an Allen wrench. When a case sticks in a resizing die, remove the die from the press. Moving the expander ball as high as possible within the die body will reduce the chances of damaging it when extracting the case.

An Allen head cap screw is threaded into the case, through the base of the extractor body. Tightening the Allen screw steadily draws the stuck case out of the die, until it comes free.

Using the drill bit provided in the kit, drill through the head of the case at the primer pocket. Next, use the tap to thread the hole just drilled. With the hole threaded, place the base over the head of the case. Run the cap screw through the hole in the base unit, thread it into the case, and tighten the screw against the base unit. Continuing to tighten this screw will slowly but firmly draw the case out of the die. Although they are rarely needed, a stuck case remover should be a part of every reloader’s equipment. When a case sticks, these kits provide the only reliable method of removing it, with minimal chance of damaging the die. There may be some difference between the kits offered by different manufacturers, but most will operate on this same principle.

Next time, lubricate the case properly before attempting to resize it.

In some instances, cases may become stuck in the die when the head is pulled completely off, as in a case head separation. If this happens, returning the die to the manufacturer is probably the best option. Most will correct such problems for a small fee. A stuck case remover is rarely used, but we strongly recommend purchasing one before it is needed. They are inexpensive insurance when it comes to avoiding the aggravation caused by this situation. By properly lubing cases before resizing, and using the correct shell holder, the need for one may never arise.

Case gauges are typified by these two from Dillon Precision. These simple chamber type gauges are also available from L.E. Wilson, Midway and others.

Headspace/Case Length Gauges

Within the last few years, reloaders have become much more knowledgeable concerning some of the more technical aspects of handloading. This increased awareness has resulted in the widespread use of case gauges, run-out indicators, and headspace gauges. Headspace gauges have been available for decades, but have been little used by other than competitive shooters and those perfectionists dedicated to achieving the ultimate in accuracy.
In use, a resized case or loaded cartridge is dropped into the chamber of the gauge, as shown in this photo. The head of the case should stop between the small steps cut into the base of the gauge, indicating correct headspace.
Most of these gauges are essentially a chamber, cut for the particular cartridge being gauged. When a cartridge is inserted into the chamber, the case head will be flush with the base of the gauge. Cut into the base is a small step (normally .004" to .005"), which indicates correct headspace. If the case head is below the bottom step, it has excessive headspace; above the top step shows insufficient headspace. When the head is flush with, or between the two steps, the cartridge is correctly headspaced. If the rifle’s chamber is correctly cut within SAAMI specifications, this cartridge will fit the chamber properly. Many of these gauges also have another step cut into the case mouth end of the die, allowing it to double as a case length gauge.
An RCBS Precision Mic is used to check the head-space dimensions of a loaded cartridge. Unlike the chamber type gauges, the RCBS unit gives an exact measurement of head-space, allowing for very precise die adjustment.

RCBS is now marketing the headspace gauge known as the Precision Mic. This differs from the chamber type headspace gauges in that it uses a micrometer type head assembly to allow a direct reading off the
case being measured. With a base unit supporting the case head, the Precision Mic uses a “headspace nut” which is screwed down to the case shoulder. This allows a reading from the datum line to be taken from a micrometer-like scale on the side of the body and headspace nut. This, in turn , allows the handloader to adjust sizing dies to exactly the correct headspace of the particular rifle being loaded for, even if the rifle’s chamber does not fall within SAAMI specifications. This unique little gauge also has a bullet seating unit that allows for a reading to be taken directly from an individual rifle’s throat. Armed with this reading, seating dies can be adjusted to give the same amount of “freebore” or “bullet jump” even when different styles or profiles of bullets are used. This accomplishes exactly the same purpose as a comparator, giving a reading that can be used for establishing seating depth for a given chamber/bullet combination.
In use, either a resized case or a loaded cartridge is placed in the body of the Mic. The top portion of the Precision Mic is then screwed down onto the body unit until it contacts the shoulder of the case. A reading can then be taken off the vernier scale on the side.


Neither of these units should be confused with the gauges used by gunsmiths to check headspace in the firearm itself. These are normally sold in sets of “Go” and “No-Go” gauges, and (for rimless cartridges) resemble a solid steel cartridge case. In use, each gauge is chambered in the firearm. The “Go” gauge should just allow the action to close. When the “No-Go” gauge is chambered, it should not allow the action to close. If this criteria is met, the headspace for the firearm is correct. When describing headspace, it must be clearly understood that we are discussing a combination of measurements, and that headspace problems may exist in properly cut chambers if the ammunition is not correct. Conversely, ammunition that is “properly” headspaced will give trouble in a firearm chamber that is not correct.

Specialty Dies

Reloading has undergone drastic evolution within the past decade. The rise in high volume shooting sports such as IPSC/USPSA has given a tremendous boost to the popularity of progressive reloading presses. Reloading manufacturers have responded by making some obvious changes to their die lines. Fifteen to twenty years ago, carbide sizing dies for pistol cartridges were uncommon; today, they are standard equipment for most reloaders. The die functions have been altered as well. In the past, sizing dies often performed the sizing operation only. The decapping was performed in the #2 die, simultaneous with the expanding/belling operation. This has now been changed by virtually all manufacturers, so that the decapping is performed in the sizing die. The change was made largely to accommodate the rising number of progressive presses in service. Redding has gone so far as to offer a series of pistol dies designated as their “Pro-Series” for use specifically with progressive presses. These dies have no expander, since the more popular presses of this type do not require one. Most expand the case mouth and charge the case with powder via a special expander/powder funnel attached directly to the powder measure.

Dillon’s New Dynamic pistol dies are an excellent example of dies that have been designed specifically to function in a progressive press. With a cavernous opening in the base, this helps to speed the operation by allowing the cartridges to align themselves as they enter the die. They also have several other features that make their use in progressive presses extremely advantageous. The down side is the fact that these specialty dies cannot be used in conventional single stage presses without purchasing an expander unit separately. Know your equipment, and base your purchases on your particular needs.

Lee’s Factory Crimp die is still another example of a specialized tool made to perform a specific task. Equipped with a carbide sizing ring, these unique dies size the assembled cartridge again after the final crimping, as well as applying the correct style of crimp. This assures that any bulging or out of roundness will be ironed out. Sierra has always advocated that crimping be applied in a separate operation rather than being done in conjunction with bullet seating. These specialized dies take this approach one step further, guaranteeing that the finished, reloaded ammunition will be below the maximum allowable dimensions. This final step goes a long way in making certain that your ammunition is as reliable as it can possibly be. Again, specialty dies made for a specific purpose (but not necessarily required for “conventional” reloading) may offer a significant advantage for certain applications.

Case forming allows the reloader to use firearms chambered for obsolete or hard-to-find cartridges. Here, a 7.62mm Tokarev has been formed from a 9mm Winchester Magnum case.

Decapping dies, such as those available from Lee and Lyman, are particularly useful for decapping military cases. With their crimped in primers, military brass can be extremely hard on standard decapping units. Dedicated decapping dies usually use an extra heavy-duty decapping pin that is solidly affixed to the decapping rod. Attempting to decap military brass with the decapping units found in standard resizing dies will often result in bent or broken decapping pins. Specialty dies of this type will make this task much less frustrating. The models offered by either Lyman or Lee are universal dies, capable of being used with almost any standard cartridge. As such, you will not need a separate die for each caliber being processed. Since they perform no type of resizing, lubrication is not required when using a decapping die.


Case forming can provide an economicalsource of cases, such as the .221 Remington
Fireball which can be formed from economical 5.56mm NATO brass. Case forming dies are available from Redding, RCBS, and others.

Forming dies offer the reloader the chance to economize by reforming cases that may be more readily available, into those that are more costly, hard to come by, or dis- continued. Cases for the .221 Remington Fireball, for example, can easily be formed from surplus 5.56mm NATO brass. Custom wildcats, too, often require special forming dies to allow the parent case to be gradually shaped into the new conformation. For more information regarding specialized form dies, RCBS and Redding Reloading probably offer the best selection on a stock item basis.

Match Grade or Bench Rest Seating Dies

As the accuracy potential of the average firearm has improved, shooters have become much more demanding as to what level of accuracy is considered acceptable. With a number of single shot handguns now being chambered for bottlenecked cartridges like the .223 Remington, rifle-like accuracy has become commonplace. In response, many reloading tool manufacturers have refined their seating dies to allow for straight line bullet seating. This type of die utilizes a sliding chamber that fully supports the cartridge case as the bullet is seated. The
A straight-line seating die (left) compared with a conventional seating die (right). Primary differences are the spring-loaded sleeve used to insure concentricity and the micrometer adjustable seating stem. Commonly referred to as benchrest or competition units, this type of die has become quite popular among competitive shooters, long-range varmint hunters, and others concerned with getting the utmost accuracy from their equipment.

purpose of this is to align the bullet with the case mouth perfectly before beginning to seat it. This is an aid to assure the utmost concentricity, removing yet another variable from the reloading process. Benchrest shooters have been using straight line hand dies (the die body is not threaded, and they are not used in a conventional reloading press) for decades, but it has been more recent that they have become popular for use by the “average” handloader. Bonanza was one of the first to offer these dies for a variety of popular calibers, but they are now available from most of the major reloading tool makers as well. Before purchasing a straight line seating die, consider the use to which it will be put. If you are dealing with a big game hunting cartridge that routinely shoots groups in the 1 3/4 to 2 MOA range, it is doubtful that these dies will give any noticeable improvement. If the pistol in question is a tack-driving varminter already giving MOA performance, benchrest or competition grade dies are a worthwhile investment. In our daily quality control testing, bullet seating in the Sierra lab is accomplished with benchrest dies almost exclusively. For the level of accuracy that we require, conventional seating dies are frequently not up to the task.