Improved Wildcat Cartridges

An Improved cartridge is essentially an enlarged version of an existing cartridge, fireformed or expanded in the forward half of the case body and shoulder over the parent cartridge. These cases are normally headspaced on the same neck and shoulder datum line as it is fire-formed in the new chamber. The end result is a cartridge that holds a greater volume of powder, thereby increasing its velocity and often its overall performance. The process is not always without some cartridge loss due to case cracks or splits.

There are obviously caveats to be observed by the shooter if sound practices are not followed. Typically, the reamer used for an Improved cartridge is headspaced on the neck shoulder or case datum line. As a result, the case is correctly headspaced and ready to be fireformed, resulting in anew version of the cartridge. Attempting makeshift headspacing techniques can lead to real problems and locked up or blown rifles. One such risky procedure is to use along-seated bullet in an attempt to establish headspace.

That is where a longseated bullet makes firm contact in the leade or throat of the chamber as a means of headspacing. There are always added problems where the Wildcat or Improved cartridges are much shorter than the chamber they are to be formed in, particularly forming rimless cartridges.

Three typical cartridges pictured from left are the .30-06 Improved, fire formed from the .30-06 cartridge; .257 Improved, fire-formed from the .257 Roberts, dating back to 1934; the 5.6×44 SW-NEJ cartridge, a straight wall cartridge designed by author, fire-formed from the .223 Remington cartridge. Standard .223 Remington cases can readily be fired in this Improved chamber for target or hunting.

As a rule it is strongly advised to stay away from any Wildcat or Improved cartridge where the new reamer doesn’t allow headspacing off the neck shoulder datum line of the chamber. The Fire-Forming Process Over the past 60 years I have fireformed a great number of Wildcat and Improved cartridges, including those existing and a good number of my own design. I have done so without untoward incidents and have always looked forward to each new version, whether my own or for others.

Many have shown noticeable improvement in both accuracy and velocity. The Improved case is usually formed from cartridge cases with headstamps of like designation, i.e. .257 Improved originates from the .257 Roberts; the 6.5/06 is the .30- 06 necked down to the 6.5mm bullet. There are scores of interesting possibilities. The question is often asked relative to the powder charge used in fire-forming a cartridge.

In my own experience, powder charges used to fire-form cartridges are about midway in the reloading manual for the parent case. I normally use a medium burn rate of powder and a medium bullet weight for case forming. Sometimes I’ll go close to maximum as pressure signs are

Far 6×44 SW-NEJ resulted in a very practical Improved version of the .223 Remington. This was accomplished with a near straight wall reamer and a 60degree shoulder up to the neck-shoulder datum line. There is no .223 Improved case with greater powder volume. Headspaced on the neck-shoulder datum juncture, standard .223 Remington cartridges can safely be fired in rifles chambered for the Improved cartridge with outstanding results.. 223 Remington cases in the 5.6×44 SW-NEJ cartridge.

Load used was 73 grain Berger bullets ahead of 22 grains of Hodgdon Varget powder. The bore break-in was combined with case fire-forming resulting in 50-yard groups under 1/4 inch. The barrel used here was a five groove Pac-Nor match select. Note the difference in the case shoulder and body taper of the fired and unfired cases. Working with Improved and Wildcat cartridges can be a very fulfilling endeavor both for the gun owner and the gunsmith. carefully observed.

Of course, the newly formed case will later receive a greater charge of powder as it is designed to do. I believe the new case should fully obturate the chamber on the first firing. This will result in fewer split or asymmetrically formed cases. Overall case shape or size seems to have little bearing on the final outcome. 223 Remington (five rows on right) to 5.6×44 SW-NEJ (five rows on left) show the interesting possibilities for both the gunsmith and shooter.

With further regard to the use of different powders in case fireforming or subsequent handloading there is a warning we must heed. There is overwhelming evidence that reduced charges of slow burning powders can cause detonation resulting in extremely high pressures and blown guns. This would include any of the slow burning powders like 4350, 4831, et al. While this may apply more to larger overbore cases, all cartridges must be included, both in cartridge fireforming and general handloading.

The state of case/shoulder malleability does, however, have a direct bearing on case forming. Cartridge cases are an alloy consisting essentially of copper and zinc in variable proportion capable of being annealed through varying degrees of heating and cooling. Some brands of cases are pre-annealed. If cases aren’t age hardened or over worked through repeated shooting and resizing, case loss should be minimal,

Rifling twist rate should also be included as it is important in bullet stabilization. From left, case fired in chamber, round head screw to be tapped into drilled out primer pocket, drill bit and 10-32 tap. if at all, particularly with new brass. I have perhaps annealed less than 15 percent of my Improved or Wildcat cases with very little loss due to case cracking or splitting.

I often use the shoot-and-clean bore break-in with case fire forming and usually see accuracy quite representative of that barrel’s potential. I usually break in a bore at 50 yards and like to see those early small groups while using good components. Polishing Chamber Walls Despite our best efforts at reaming a chamber, there will be some minor imperfections remaining as circular striations.

This can easily be removed or decreased by rotating a fully fireformed case into the chamber covered by a coating of J-B Non-Embedding Bore Cleaning Compound or other polishing medium. As a means of holding the case in an electric drill or lathe, I drilled and tapped the case head for a socket head screw. Just a short session of polishing will do the job… don’t over do it. Polishing will also assist our efforts in getting a more uniform, fully-sized case.

As a means of complete fire-forming of the case shoulder area I apply a very thin film of sizing lube to the Such illustrations and warnings as noted in the Hornady 10th Edition Handbook of Cartridge Reloading serve as a warning. "For example: Comparison of the .222 Magnum and .223 Remington show case size near identical in appearance.

However, the .222 Magnum is about one tenth of an inch longer and holds 1/2 to 1 grain more powder. .223 cartridges should not be fired in a .222 Magnum chamber as the case dimensions are different and the cases are likely to rupture, possibly causing injury." I cite this example not to discourcase just below the shoulder and through the case neck. This does wonders in totally forming this area of the case. Some of these little things sure can make our job a lot easier and more effective.

In the final analysis, fire-forming Improved or Wildcat cartridge cases holds little mystery. But the gunsmith and the reloader/shooter of such cartridges should develop a good working knowledge of the fundamentals involved. There’s a pretty good chance you may even enjoy doing it while you’re at it. AG age but as a reminder to always be alert and exercise reasonable caution in one’s selection of cartridges used in Improved or Wildcat cartridges.