Stepped Neck Benchrest Cases


#1

While no shooter can prove that one particular neck length or degree of neck tension is superior to another, all will agree that round-to-round uniformity of tension is vital to accuracy. Such uniformity is usually achieved by reaming or turning case neck walls to a consistent thickness and then using a sizing die that will result in the individual shooter’s concept of ideal neck tightness, or looseness. Other methods, such as closely fitting the case neck to the chamber, which results in no expansion upon firing, have been tried with varying degrees of success. One shooter resolved the problem to his own satisfaction simply by using a single, carefully prepared cartridge case, reloading it at the bench for each shot. It worked after a fashion but wasn’t too practical, especially when the time allotted to fire a group began to run out. Even earlier, many shooters seated their bullets directly into the chamber’s throat effectively eliminating the need for a case neck.

Years ago several Benchrest shooters used what is called a stepped neck. A stepped neck case is a specially prepared cartridge case that is closely fitted and matched to the individual rifle and is not interchangeable with other rifles. Very precise measurements of the chamber, bullet, and neck diameter of the cartridge case are taken. After calculating the proper dimensions, the outside diameter of a new case neck is reduced, but only to the point on the neck where it is determined the base of a loaded bullet should be. The case is then loaded and fire-formed. When the neck expands to fit the chamber walls, it reverses the outside turning process and creates a step inside the neck for the bullet to sit on. To load the case, the fired primer is knocked out, a new primer seated, a powder charge is thrown, and the bullet slipped into the case with the fingers. Voila! No neck tension means uniformity to the nth degree.

Identifying a stepped neck case takes only a few seconds. Look for a very slight ring on the outside of the neck between the shoulder and mouth. This is the last vestige of the place where the outside neck turning was stopped. The step may or may not be visible inside the neck but can usually be felt with a sharp pencil point. Inserting a flat-base bullet of the proper caliber should result in the bullet sliding smoothly into the case and then stopping at the location of the step.

Those shown here were all used in competition. On the left is a 308W case with a new shoulder partially formed and the neck outside turned, ready for fire-forming. Next to it is the completed case with a stepped neck, a .30 x 50 Improved (.308W shortened to 50mm with a 40-degree shoulder). Next is a .23-40 (.223 Remington with a 40-degree shoulder) with a stepped neck. On the right is a very unusual benchrest cartridge. It is a .22BR Short (1.390" CL) with the rim lathe-turned to .222 Remington dimensions, and a stepped neck. Like most benchrest shooters, the users of these three cartridges hedged their bets and combined the stepped neck with other changes in case shape and dimensions.

Stepped neck cases worked exactly as intended but are never seen on the firing line today. Shooters learned that the time and labor to prepare such cases seldom, if ever, resulted in accuracy gains over the simpler methods of controlling neck tension. They are, nonetheless, a unique part of benchrest and unless identified and preserved will soon be lost to history.


#2

Bench rest types certainly are fanatical innovators. Thanks for sharing, although few will want to imitate their fanaticism.


#3

John

We prefer to think of ourselves as excessively enthusiastic.

Anything goes in the quest for that one-hole group.

Ray