It’s All About the Wildcat Cartridge

I thought a good topic to discuss would be one that we don’t hear about much these days and that is wildcat cartridges. The term wildcat cartridge is used to describe a custom-made cartridge, most often inspired, and made by modifying an existing commercial cartridge. It is usually developed by individuals to optimize a given cartridge’s performance to obtain more power, more velocity, flatter trajectory, or better accuracy, etc.

Because they are custom-made, they are not available the way commercial cartridges are. Because of the limited market for them, commercial cartridge manufacturers generally don’t manufacture them until they generate a large enough following. Wildcat cartridges are most often deep in the domain of very serious shooters or handloaders.

Specific Needs

Because individuals create the need for a wildcat cartridge, there are more varieties of Wildcat cartridges than commercial production cartridges. Most wildcats are produced in very small quantities compared to their commercial counterparts. In some cases, cartridges start out as custom-made Wildcat cartridges, because the originator wants to solve a specific ballistic challenge. Sometimes, his efforts gain enough popularity that they become commercialized, and rifles chambered for them become available commercially with SAAMI standards specified for them.

A famous example of successful cartridge experimentation involving an existing cartridge is that of the .357 Magnum, which was originally developed from the .38 Special cartridge. Early versions of .357 Magnum were identical in size to .38 Special cartridges. The .357 and .38 Special cartridges are both the same diameter externally and only differ slightly in length because of safety reasons. The length was increased slightly so that you could not accidentally load the more powerful .357 Magnum cartridges into a firearm not designed for the additional pressure.

Another example of what a wildcat would be is the 6.8mm SPC, which was originally developed in collaboration with members of U.S. SOCOM. The 6.8mm SPC is based on a .30 Remington cartridge. It was then modified to .270 caliber and then further modified in length to fit in magazines that can fit the magazine wells of the M16 rifle.

Any M16 or AR15-type rifle only needs to replace the barrel, bolt, and magazine to use this new cartridge. This cartridge is more effective than the standard NATO 5.56x45mm cartridge fired by the M16. Though it has not been officially adopted by the military, it has found use by special forces troops in Afghanistan and Iraq, and is gaining popularity as a commercial civilian round.

Another example of a very successful cartridge that started as a Wildcat is the 6mm PPC (Palmisano & Pindel Cartridge, named after its inventors, Lou Palmisano and Ferris Pindell). That cartridge started out as an improvement of the .220 Russian cartridge, which was itself based on the 7.62x39mm cartridge used in the AK-47 and AKM rifles.

The 6mm PPC case is made by forming the .220 Russian brass case into a new shape and is specifically geared for single-shot benchrest shooting. It became one of the most accurate cartridges available out to 300 yards and has been produced commercially since 1975. Its design concept validated the short wider powder column concept for accuracy.

Barrel Modification

As stated previously, wildcat cartridges are generally used by serious shooters. This is because wildcat cartridges often require barrel modifications to be used. The modified barrels are usually supplied by custom barrel makers, who typically work out of small shops.

Custom barrel makers will also supply the buyer with reloading tools and dies, so the buyers can make their own cartridges. Some barrel makers also supply data about how different powder brands, quantities, and bullet weights perform with their barrels. Many wildcat cartridges have been developed by custom barrel makers or by someone who is working in conjunction with a custom barrel maker.

A wildcatter usually starts out using a commercial cartridge case they think can be improved by changing its shape to new dimensions. Usually, this involves pushing the shoulder of the cartridge backward or forward as needed to modify the case capacity. The wildcatter will also change the diameter and length of the cartridge neck. This process can be done by either cold forming (i.e., the case is pushed into a die and pressure is applied to change the shape of the case) or fire forming (i.e., the case is placed in a chamber of a different dimension and loaded with a light gunpowder charge. Upon firing the charge, the case takes the shape of the new chamber).

Sometimes a mixture of both methods is used to make the final case shape of a wildcat cartridge. Next, the wildcatter trims the case to the appropriate length, because cold forming or fire forming generally tends to increase the length of the case’s mouth and the excess length needs to be trimmed. Then the diameter of the neck is changed as needed for the new bullet. The cartridge is then hand-loaded carefully and a bullet is seated.

One of the most famous wildcatters of all time was P.O. Ackley. He was credited with the modifications known as the Ackley Improved Series of cartridges. In this series, he reduced the taper of the case and the angle of the shoulder which increased the propellant capacity of the case, ergo increasing its performance.

The entire family of Ackley Improved Cartridges was developed by Patrick Otto Ackley. Ackley was also a prolific gunsmith and author. He produced many improved versions of commercial cartridges in various calibers.

When I was young, dumb, and new to the firearms community, I used to go to Bob Hutton’s Rifle Ranch in Topanga Canyon California. Bob Hutton was the technical editor of Guns & Ammo magazine from 1959 to 1974 and a very respected ballistics expert. On one shooting trip, I was fortunate enough to meet Mr. Ackley while he was visiting Bob and doing some testing. Back in the day, Southern California was where everything shooting was happening.

Most firearms can be easily modified to use the Ackley Improved Series of cartridges. For example, the .243 Ackley Improved cartridge shown above could easily be used by rechambering an existing .243 Winchester firearm. An advantage of all “Ackley Improved” firearms is they can also fire standard, factory-loaded ammunition. This allows the owner to use commonly available ammunition, should he or she run out of wildcat cartridges.

Another interesting wildcat that became a commercial success was the .458 Lott. For those of you not familiar with Jack Lott, he was a big game hunter and writer. I had occasion to be seated with Jack Lott at a Professional Hunters dinner prior to the introduction of the .458 Lott Cartridge. Lott told of its genesis, and his adventures in the bush war of Mozambique, in a very interesting fashion.

In 1959, Jack had an adverse encounter in Mozambique with a Cape buffalo, in which he was injured. He had been hunting with the then-new .458 Winchester Magnum. That experience convinced him that a more powerful cartridge than the .458 Winchester Magnum was required for hunting dangerous game. After the encounter, he began a search for a big bore cartridge that would suit his needs more perfectly.

The .458 Winchester Magnum that almost got Jack killed was put into production in 1956 and was an immediate commercial success. At the time it was a more economical alternative to the English double rifles that were considered the standard for dangerous game hunting in Africa. The .458 Winchester Magnum promised to emulate the performance of the .450 Nitro Express in a cartridge designed to fit a standard-length bolt-action rifle.

From reports coming in from the field, it soon became apparent that the .458 Winchester Magnum was not performing as anticipated. Several factors contributed to its less-than-stellar performance in Africa. The most notable problem being it never generated the power required to be effective. Jack’s search did not find a cartridge that would fill his needs, so he set out to design a cartridge to fulfill his needs in a dangerous game cartridge.

Jack Lott’s original concept drawings of the cartridge were done on a napkin during a diner engagement. It was based on the full-length .375 H&H Magnum blown out and shortened to 2.800 inches. The first cases for the new rifle cartridge were fireformed from .375 H&H Magnum brass in a .458 caliber chamber. The .458 bullets had their bases resized to .375-inch, so they would fit in the mouth of the .375 H&H Magnum case. This method of fire forming left the newly formed cases slightly shorter than the parent cases. The resulting cartridge was named the .458 Lott in Jack’s honor.

While the cartridge was slow to gain popularity at first, Jack’s effort became the standard by which dangerous game cartridges are now judged. As intended, the cartridge provides a distinct step up in performance over the .458 Winchester Magnum. As a side note in honor of our friendship, I had a custom rifle built and chambered in .458 Lott.

I hope this helps clear up any misconceptions you may have had concerning Wildcat Cartridges and perhaps inspires you to create the next great do-everything Eargesplitten Loudenboomer. Stay Safe!

Do you have a favorite wildcat cartridge? Share it in the comment section.