The 6mm PPC (Palmisano & Pindel Cartridge), 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 long, and aggressive shoulder angle of 30 degrees. Its primary use has been benchrest shooting matches since the 1980s. Background The cartridge is a necked-up version of the .22 PPC which is in turn based on a .220 Russian (5.6×39mm). The standard bullet diameter for 6 mm caliber cartridges is , the same diameter used in the .243 Winchester and 6mm Remington cartridges. To obtain maximum accuracy, bullet weight and form are matched to the rifling twist rate of the barrel. Typically, bullets are used in barrels with twist rates of 1 in 13 inch (1 in 330 mm), while 1 in 15 inch (1 in 380 mm) barrel twists can accommodate lighter accurately. The cartridge developed enough acceptance that rifles chambered for it are available commercially. Converting cases The parent cartridge for the 6PPC is the .220 Russian (5.6×39mm), which in turn derives from the 7.62×39mm. Brass can either be purchased or formed from .220 Russian brass. Recently, European cartridge manufacturers Lapua, Norma and SAKO have begun making 6mm PPC brass. During its early development, accuracy experts noted that perfectly concentric thicknesses of the cartridge neck were beneficial in aligning the bullet with the bore. Most 6PPC chamber reamers are ground with a tight neck section to create a cartridge with a concentric fit and consistent neck-to-chamber clearance. This contributes to the 6PPC's accuracy. To convert an existing .220 Russian case, the case first is lubricated and sized in a 6PPC die. A pistol primer is then inserted into the case and the case is filled with fast-burning pistol propellant. Paraffin wax is then melted into the lid of a jar and pressed it over the neck of the cartridge to seal it. At this point, the case has been made into a blank cartridge. The case is fire formed in a 6mm PPC rifle, expanding the case powder capacity. The fire formed case is cleaned to remove lubricant and powder residue. The neck is then expanded to 6 mm and the case length is trimmed to , after which the neck