Making a Custom Case-Neck Expander Die

Reworking case necks to accept larger-diameter bullets is a procedure often performed by handloaders. This is particularly true for the wildcat cartridge aficionado who sometimes needs a case neck expanded up a few calibers. This was the issue when sizing a 243 Winchester Super Short Magnum case neck to 6.5mm (.264) diameter. Each caliber increment in case neck diameter normally requires passing of a different expander-button through the case mouth. There is a better way.

A three-diameter stepped expander requiring but a single pass of the expander button into the case mouth does a perfect job. Making a three-step expander button to upsize a .243" neck to .264" neck to fit into a 7/8" x 14" standard reloading press involves only basic shop procedure. First, I found a 7/8" x 14" sizing die body with a suitably large enough case neck expander button to be reformed into a threestep expander.

The hardened expander button began at .30 caliber with sufficient length to form into three graduated steps from .250", .256" and .262". A carbide tool bit was required to make the steps and 600 grit (15 micron) silicon carbide mesh paper was used as a button polishing medium. There is some leeway in making the three-step expander because the cases must later be run through a standard reloading die specific to each cartridge before the case is charged with powder and a bullet is seated.

Steps shown here are graduated from .250" to .256" and finally to .262". This expander button is made to form a .243 case neck to .262" with a single pass into the expander die. With the expander button in place inside the 7/8" x 14" die, attached via the adjustable, threaded rod, check to see if it extends beyond the die mouth opening. If the die mouth isn’t large enough for the new case to enter, the die must be cut off so the stepped expander button extends fully beyond the die mouth.

This is necessary to prevent an overly-large cartridge case from jamming into the smaller die opening. The threaded die is just a means of holding the stepped expander button in alignment with the case while re-sizing the case mouth. Annealing Case Necks Before case necks are expanded more than one caliber they should be properly annealed. This prevents work hardening of the brass during forming and repeated reloading operations, a condition that often causes necks to split.

There are a few ways case necks can be annealed. One very effective means of doing it is to have cases standing upright in a pan with water covering the base of the unprimed case. The case neck is then heated with a small torch to the point of discoloration or a cherry red color and then tipped over into

From left, cut down die body, stepped expander button on threaded shaft, die shaft adapter with lock nut and lock ring collar. The case on the left is an unaltered .243 WSSM case with case on right annealed, shortened and expanded to .262" inside the neck. the water. The other way is to have a means of rotating the vertical case as the neck and shoulder are heated and then dropped into room temperature water.

An excellent way to rotate cases is to use one of the electric case mouth chamfering tools with a fixture to hold the upright rotating case. A simple, cup-like fixture made of brass and threaded to fit one of the stations does a perfect job. A forceps or needle-nose pliers is used to place cases into the rotating fixture as the 243" to .262" with a single pass over the stepped expander button. properly directed flame heats the case neck and shoulder.

Sometimes the resized cases will later require outside neck turning to uniform the wall thickness and trimming to length. Then, with a good case sizing lube applied to the case mouth, an easy, single pass of the stepped button performs a perfect upsizing of the case neck. These cases will then withstand repeated reloading without case loss due to neck splitting. AG