6mm PPC

Type

Rifle / Competition

Place of origin

USA

Production history

Designer

Lou Palmisano / Ferris Pindell

Designed

1975

Specifications

Parent case

.220 Russian

Case type

Rimless, bottleneck

Bullet diameter

.2430 in (6.17 mm)

Neck diameter

.262 in (6.7 mm)

Shoulder diameter

.431 in (10.9 mm)

Base diameter

.441 in (11.2 mm)

Rim diameter

.445 in (11.3 mm)

Case length

1.515 in (38.5 mm)

Overall length

2.100 in (53.3 mm)

Rifling twist

1-14"

Primer type

Small rifle

Ballistic performance

Bullet mass/type	Velocity	Energy
60 gr (4 g) HP	3,300 ft/s (1,000 m/s)	1,452 ft·lbf (1,969 J)
70 gr (5 g) SX	3,250 ft/s (990 m/s)	1,641 ft·lbf (2,225 J)

Test barrel length: 24"
Source(s): Accurate Powder

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. At distances out to 300 yards, it is one of the most accurate cartridges available. This cartridge's accuracy is produced by a combination of its stout posture, being only 1.23 inches (31 mm) long, and aggressive shoulder angle of 30 degrees compared to a 30-06's 17 degrees. Today it is commonly used for railgun shooting matches and has been since the 1980s

The cartridge is a necked-up version of the .22 PPC which is in turn based on a .220 Russian. The standard bullet diameter for 6 mm caliber cartridges is .243 inches (6.2 mm), 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, 68-grain (4.4 g) bullets are used in barrels with twist rates of 1:13 (one twist for every 13" in the barrel), while 1:15 barrels can accommodate lighter 58-or-60-grain (3.8 or 3.9 g) accurately. The cartridge developed enough acceptance that rifles chambered for it are available commercially.

The parent cartridge for the 6PPC is the .220 Russian, which in turn derives from the 7.62×39mm. Brass can either be purchased, or formed from .220 Russian brass (7.62×39mm can also be used, but .220 Russian brass is usually higher quality and thickness, since it is designed to operate at higher pressures).

During the early development accuracy experts noted that perfectly concentric thickness of the cartridge neck were beneficial in lining up bullet to the bore - a feature mostly lacking in commercially available brass of the time. Most 6PPC chamber reamers are ground with a tight neck section that requires removing some case neck material ("turning the necks") to create a cartridge with a concentric fit and consistent neck-to-chamber clearances which contribute to the 6PPCs accuracy. While the SAAMI specification for neck thickness in a 6mm cartridge is usually .272 inches, it is common to see 6PPCs with .262, .268, or .269 custom neck sizes, hence modern factory ammunition is not commonly produced for the 6PPC as it would be dangerous to shoot in these custom chambers. To help clarify this, factory guns and ammunition are usually specified as the "6PPC-USA" cartridge which has a CIP/SAAMI specification. To the Note that a neck expanded, "unturned" (thickness of neck reduced) and loaded 220 Russian case neck will almost always be larger in diameter than the 6PPC rifle's chamber neck; if so, Method One does not apply—see Method Two. It is important to understand the characteristics of one's chamber before starting. Use of a "chamber cast" using Brownell's CERROSAFE® CHAMBER CASTING ALLOY or equivalent is a good way to accomplish this. Alternatively, one can use a manufacturer's print of the chamber (usually very hard to obtain, except for European manufacturers) or a print of the reamer used to cut the rifle chamber.

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Wikipedia