John Alexander

     The Lee Collet die offers some advantages worth considering by the cast bullet shooter.

     Conventional neck sizing dies reduce the case neck by forcing it into a cylindrical section of the die. Because of variations in brass thickness, the case neck must be made smaller than the desired diameter then expanded back up by pulling an expander plug through the neck. This conventional method works OK but it does work harden the brass both during the sizing down and then again when sizing back up, eventually leading to neck cracking and shortened case life.

     The expanding plugs are designed to expand the case neck to the appropriate diameter for jacketed bullets that is almost always smaller than optimum for cast bullets. After conventional sizing, cast bullet shooters often expand and flare the neck a bit with the Lyman M die to avoid damage to the relative soft cast bullets.

     There are neck sizing dies available that use replaceable bushing to size the neck down to any desired diameter without the need for an expanding plug but this type of die and the needed set of bushings are quite expensive.

     The Lee Collet die can also size the neck to any diameter needed, but uses a different principle to size case necks. Instead of sliding the neck into a die, the Collet die reduces neck diameter by squeezing the neck down by applying a force perpendicular to the neck as the case is pushed into the die.

     Since there is no sliding, no case lubrication is needed. Both grease application and grease removal are obviously eliminated. Eliminating the need for case lubrication is nice but the real advantage of the Collet die is its ability to size the case neck to any diameter. This allows the cast bullet reloader to vary the neck’s grip on the bullet from gentle to minimize bullet damage to firm to withstand rough handling. This is a very handy option when working with different bullets or with the same bullet sized to different diameters.

Improving Lee Collet Dies

     Collet sizing offers many advantages. Lee collet dies size with no need to lubricate case necks or the necessity of cleaning the lube off afterward. More important, they avoid passing the neck over the expander which can stretch the case as well as pull the neck off center. Neck expanding tends to worsen any eccentricity between the inside and outside diameters. Collet sizing over a mandrel tends to make it better.

     Good as they are, Lee collet dies can be improved. I begin by disassembling the die and stoning off the circumferential tool marks on the tapered end of the collet using first a coarse brown stone and finishing with a white Arkansas. Next I shorten the collet to leave about .03" at the case mouth un-sized. A fired case in the collet supports the fingers while the end is turned off. Light grease on the tapered surface before reassembling helps break in the die and ease operation.

     Cases sized in the shortened collet die need no chamfering at the mouth to have a very smooth step inside the case neck to ease seating the bullet. The un-sized mouth also helps center the front of the case in the chamber. Sacrificing one cartridge case to shorten the collet is a small price to pay for these improvements. The smooth step will be particularly appreciated when seating plain base cast bullets. Military and other rifles having loose chambers stand to benefit most from the centering guidance of un-sized case mouths." Robert N. Sears, Falls Church, VA

     A Note on the Lee Collet Die by Joe Brennan: I have used Lee Collet Dies in 30/30 and 223 Rem, and sold them because they each collapsed a few case necks. I adjusted them and polished the innards and worked with them over the course of six months and many hundreds of cartridges. Occasionally the neck of the cartridge case would be forced downward, collapsing into the body of the case. This happened often enough that I sent them down the road. Many people use and like these dies, so perhaps my experience is atypical.