Wildcat cartridge

A wildcat cartridge, often shortened to wildcat, is a custom cartridge for which ammunition and/or firearms are not mass-produced. These cartridges are often created in order to optimize a certain performance characteristic (such as the power, size or efficiency) of an existing commercial cartridge.
Developing and using wildcat cartridges does not generally serve a purpose in military or law enforcement; it is more a hobby for serious shooting, hunting, gunsmithing and handloading enthusiasts, particularly in the United States. There are potentially endless varieties of wildcat cartridge: one source of gunsmithing equipment has a library of over 6,000 different wildcat cartridges for which they produce equipment such as chamber reamers.
Development of a wildcat.
Often, wildcats are commercially sold rounds that have been modified in some way to alter the cartridge's performance. Barrels for the caliber are originally manufactured by gunsmiths specializing in barrel making. Generally the same makers also offer reloading dies, tools to custom-load bullets into cases. Because changing the barrel of a gun to accommodate custom cartridges requires precision equipment, most wildcats are developed by or in association with custom barrel makers. Ammunition is handloaded, using modified parent cases and the gunsmith-provided wildcat dies. Generally the supplier of the barrel or dies will also provide the buyer with basic reloading data, giving a variety of powders, charge weights, and bullet weights that can be used for developing loads. Handloaders use the data to develop a load by starting with minimum loads and carefully working up.
Wildcat cases and cartridges can be found for sale, but only from small makers. Larger manufacturers usually do not produce wildcats because there is such a limited market for them and because there are no established CIP (Commission Internationale Permanente Pour L'Epreuve Des Armes A Feu Portatives - Permanent International Commission for the Proof of Small Arms) or SAAMI standards, which causes liability concerns.
Wildcat goals and methods.
Wildcat cartridges are developed for many reasons. Generally, the goal is to optimize some characteristic of a commercial cartridge in a given context. Higher velocities, greater energy, better efficiency, greater consistency (which yields greater precision) and complying to a minimal permitted caliber or bullet weight for the legal hunting of certain species of game in a particular jurisdiction are the top reasons. The sport of metallic silhouette shooting, has given rise to a great number of wildcats, as several rifle rounds are adapted to fire from a handgun. In using autopistols for hunting or competitive shooting, improved feeding of softnose or hollowpoint bullets is also an issue; the bottlenecked .45/38, for instance, was created because the straight-cased .45 ACP had trouble feeding hollowpoints.
Wildcat cartridges are generally developed because:
Some methods used to develop a wildcat are:
Example wildcat cartridges.
In terms of sheer numbers of varieties, there are more wildcat cartridges than there are production cartridges. Most wildcats are custom made, and therefore are not generally well-known. Some wildcat cartridges, however, are produced commercially in small quantities by small manufacturers. This is a list of some representative wildcats.
Wildcat cartridges in Australia.
In Australia, wildcat cartridges were relatively common. Most are made primarily for hunting species such as deer, kangaroo, are generally based on the .303 British because of the post war popularity of that round and of the cheap surplus Australian Lee–Enfield MkIII military rifles available. Many of these surplus rifles were rebarreled to .257 caliber, known as the 303-25. One of the unique features is that these cartridges relied less on handloading - and instead factory ammunition was produced by the Super Cartridge Company, Riverbrand, IMI and Sportco.
Since having an existing barrel rebored and rechambered was (at that time) less expensive than fitting a new barrel, a 303-25 rifle with a worn out barrel could be economically converted to .277 caliber, known as the 303-270.
The .222 Remington - a .222 Rimmed in a Martini was also commonly found. As too were the "Tini-Mite" and "Mini-Mite" cartridges, .17 caliber rimfire cartridges based on the .22 Long Rifle case.
Commercially accepted wildcats.
Some cartridges started out as custom-made (non-commercially developed) wildcats, and gained wide enough acceptance or popularity to become commercial cartridges. Generally, cartridges become popular commercially after a commercial firearms maker begins offering a weapon chambered in the cartridge. Once popular enough, funding is generated for SAAMI standards development. After SAAMI standards are in place, any firearms or ammunition maker can be sure that any products manufactured to the SAAMI standards can be safely used.
Some examples of custom cartridges that became commercially accepted are:
Commercially developed wildcats.
Though a cartridge technically has to not be developed commercially to be considered a wildcat, some commercial cartridges were developed by ammunition and firearm manufacturers by modifying existing cartridges – using essentially the same process used to make wildcats. Cartridges that are modified by being made longer (usually to make them more powerful) are for the most part only created commercially because of the difficulty of the process. One example of such a cartridge is the .357 Magnum, which was developed from the .38 Special in 1934 by firearms manufacturer Smith & Wesson.
Second (and later) generation wildcats.
Some wildcats are based not on commercial rounds, but on other successful wildcats. The .308 × 1.5" Barnes, a wildcat from noted cartridge author Frank Barnes made by simply necking a .308 Winchester back to in length (38.1 mm) is probably the best example of a wildcat that has spawned many other successful wildcats. The .308 x 1.5" case is available from a number of case manufacturers, and differs from a homemade .308 x 1.5" in that it has a small primer pocket, where the original .308 Winchester case has a larger primer pocket (the smaller primer is more suited to the smaller case capacity of the short round). There are at least 8 wildcats that are made from the small primer .308 x 1.5" brass, including some very successful benchrest rounds, including the Benchrest Remington family of cartridges, .22 BR, 6mm BR, 6.5mm BR, 7mm BR, .30 BR.
Another example is the .220 Russian, based on the 7.62×39mm. Since nearly all 7.62×39mm ammunition made in the 1970s used the complex-to-reload Berdan priming, and often steel cases, it made a poor choice for wildcatting. The .220 Russian, however, was and still is readily available in Boxer-primed, brass cases of high quality. The .220 Russian is still the parent cartridge of choice for the PPC line of cartridges, such as the .22 PPC and 6mm PPC, even though there are far more PPC chambered firearms available than .220 Russian chamberings. Likewise, the PPC line of cartridges were the parent case of the 6.5 Grendel, a long-range, high-energy cartridge for the AR-15.