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 of an existing commercial cartridge, or may merely be intended as novelty items.
The .243 Winchester (6×52mm) is a popular sporting rifle cartridge. Developed as a versatile short action cartridge to hunt both medium game and small game alike, it "took whitetail hunting by storm" when introduced in 1955, and remains one of the most popular whitetail deer cartridges. It is also commonly used for harvesting blacktail deer, pronghorns and mule deer with heavier rounds, and is equally suited to varmint hunting with lighter rounds. The .243 is based on a necked down .308 Winchester, introduced only three years earlier. Expanding monolithic copper bullets of approximately 80 to 85 grains or traditional lead rounds of 90 to 105 grains with controlled expansion designs are best suited for hunting medium game, while lighter rounds are intended for varmints.
The .204 Ruger is a centerfire rifle cartridge developed by Hornady and Ruger. At the time of its introduction in 2004, the .204 Ruger was the second-highest velocity commercially produced ammunition and the only centerfire cartridge produced commercially for bullets of .204 inch/5 mm caliber.
The 6mm PPC, or 6 PPC as it is more often called, is a centerfire rifle cartridge used almost exclusively for benchrest shooting. It is one of the most accurate cartridges available at distances of up to 300 meters. This cartridge's accuracy is produced by a combination of its stout posture, being only 31 mm (1.22 in) long, and aggressive shoulder angle of 30 degrees. Its primary use has been benchrest shooting matches since the 1980s.
The 6.5mm Grendel is an intermediate cartridge jointly designed by British-American armorer Bill Alexander, competitive shooter Arne Brennan and Lapua ballistician Janne Pohjoispää, as a low-recoil, high-precision rifle cartridge specifically for the AR-15 platform at medium/long range. It is an improved variation of the 6.5mm PPC.
The 6mm Remington rifle cartridge, originally introduced in 1955 by Remington Arms Company as the .244 Remington, is based on a necked down .257 Roberts cartridge using a .24/6mm bullet. Known for a combination of high velocity, long range, flat trajectory, and accuracy, it is suitable as a dual use hunting cartridge for both medium-sized big game and varmints. When used in the less common earlier slow twist barrels, it offers exceptional range for varmint applications. While not as commercially popular today as the .243 Winchester, the 6mm Remington enjoys a slight ballistic advantage and continues to be popular with handloaders and custom rifle builders.
The 6.5×47mm Lapua is a smokeless powder rimless bottlenecked rifle cartridge that was developed specifically for 300–1,000 m (328–1,094 yd) competition shooting by ammunition maker Nammo Lapua and the Swiss rifle manufacturer Grünig & Elmiger AG in 2005. Other common names for this cartridge include 6.5×47mm.
The .264 Winchester Magnum is a belted, bottlenecked rifle cartridge. Except for the .244 H&H Magnum and .257 Weatherby Magnum, it is the smallest caliber factory cartridge derived from the 2.85 in (72 mm) Holland & Holland belted magnum case. It was introduced in the late 1950s and early 1960s with the .338 Winchester Magnum and the .458 Winchester Magnum as one of a family of short-cased 2.5 in (64 mm) belted magnum cartridges developed by Winchester based on the .375 Holland & Holland parent case. It was officially introduced to the public by Winchester in 1959. After many years of dwindling use it began enjoying a mild resurgence in popularity in the mid-2000s among long range rifle enthusiasts and reloaders due to the high ballistic coefficient of the heavier 6.5mm bullets and increasing popularity of cartridges such as 6.5mm Creedmoor, .260 Remington, 6.5 Grendel, benchrest and wildcat cartridges in 6.5mm.
The .260 Remington cartridge was introduced by Remington in 1997. Many wildcat cartridges based on the .308 Winchester case had existed for years before Remington standardized this round.
The .257 Roberts, also known as .257 Bob, is a medium-powered .25 caliber rifle cartridge. It has been described as the best compromise between the low recoil and flat trajectory of smaller calibers such as the 5 mm and 6 mm, and has more energy, but is harder recoiling, similar to larger hunting calibers, such as the 7 mm and 7.62 mm.
The .284 Winchester is a firearm cartridge, introduced by Winchester in 1963.
Parker Otto Ackley was an American gunsmith, barrel maker, author, columnist, and wildcat cartridge developer. The Ackley Improved family of wildcat cartridges are designed to be easily made by rechambering existing firearms, and fireforming the ammunition to decrease body taper and increase shoulder angle, resulting in a higher case capacity. Ackley improved not only standard cartridges, but also other popular wildcats, and was the first to create a .17 caliber (4.5 mm) centerfire cartridge.
The 6.5mm Creedmoor (6.5×48mm), designated 6.5 Creedmoor by SAAMI, 6.5 Creedmoor by the C.I.P. or 6.5 CM or 6.5 CRDMR for short, is a centerfire rifle cartridge introduced by Hornady in 2007. It was developed by Hornady senior ballistics scientist Dave Emary in partnership with Dennis DeMille, the vice-president of product development at Creedmoor Sports, hence the name. The cartridge is a necked-down modification of the .30 Thompson Center.
The .20 Tactical is a wildcat centerfire rifle cartridge, based on the .223 Remington case, necked down to fire a 5.2 millimetres (0.204 in) caliber bullet. The .20 Tactical was designed by Todd Kindler and predates the .204 Ruger factory round. The case has approximately 0.2 grams (3 gr) less powder capacity than the popular .204 Ruger. Handloaders can get velocities with 2.1 and 2.6 grams projectiles that almost match the .204 Ruger. Furthermore, the .20 Tactical is also able to achieve these velocities with less powder than the .204 Ruger by more efficiently using high energy propellants such as Alliant Reloader 7 and Winchester 748. Based on the .223 Remington, a wide selection of brass is available, and can also be formed from .223 casings by use of a forming die.
The 6×45mm is a rimless, bottlenecked cartridge based on the .223 Remington or 5.56 NATO cartridge necked up to .243 (6mm). The cartridge is also known as the 6mm-223 Remington or 6mm/223.
The 6mm BR is a centerfire cartridge created for benchrest shooting. The cartridge is also known as the 6mm Bench Rest or simply 6 BR, and has also developed a following among varmint hunters because of its efficiency. There are two basic variants of very similar dimensions, known as the 6mm BR Remington and the 6mm Norma BR.
.30-06 Springfield wildcat cartridges are cartridges developed from a 30-06 Springfield "parent cartridge" through narrowing or widening the cartridge neck to fit a smaller or larger bullet in an attempt to improve performance in specific areas. Such wildcat cartridges are not standardized with recognized small arms standardization bodies like the SAAMI and the CIP.
The .277 Wolverine (6.8x39mm) is a wildcat cartridge. It is a multi-purpose mid-power cartridge with increased ballistic performance over the AR-15's traditional .223 Remington cartridge. The use of a modified 5.56 case means that at minimum, only a new barrel is needed to convert any 5.56-based firearm to .277 Wolverine.
The 6mm Advanced Rifle Cartridge (6×38mm), or 6mm ARC for short, is a 6 mm (.243) caliber intermediate rifle cartridge introduced by Hornady in 2020, as a low-recoil, high-accuracy long-range cartridge, designed for use in the AR-15 platform at request of a specialized group within the U.S. DoD for its multipurpose combat rifle program.
