Small arms ammunition pressure testing

Small arms ammunition pressure testing is used to establish standards for maximum average peak pressures of chamberings, as well as determining the safety of particular loads for the purposes of new load development. In metallic cartridges, peak pressure can vary based on propellant used, primers used, charge weight, projectile type, projectile seating depth, neck tension, chamber throat/leade parameters. In shotshells, the primary factors are charge weight, projectile weight, wad type, hull construction, and crimp quality.

The two modern standardized test methodologies in use are the Commission Internationale Permanente pour l'Epreuve des Armes à Feu Portatives or C.I.P. methodology, and the Sporting Arms and Ammunition Manufacturers' Institute or SAAMI methodology. The SAAMI methodology is widely used in the US, while C.I.P. is widely used in the mainly European C.I.P. member states. While both modern methodologies use piezo pressure transducer sensors to generate pressure readings, differences in the test setup mean that the same pressures will often generate very different readings depending on the method used.

C.I.P. uses a drilled case to expose the pressure transducer directly to propellant gases. The piezo measuring device (transducer) is positioned at a distance of 25 millimetres (0.98 in) from the breech face when the length of the cartridge case permits that, including limits. When the length of the cartridge case is too short, pressure measurement will take place at a chambering specific defined shorter distance from the breech face depending on the dimensions of the case. The defined distance for a particular chambering is published in the TDCC data sheet of the chambering.
In a rifle cartridge case like the .308 Winchester, the TDCC M = 25.00 value denotes the transducer must be positioned at a distance of 25 millimetres (0.98 in) from the breech face.
In a relatively short pistol cartridge case like the 9×19mm Parabellum (9mm Luger in C.I.P. nomenclature), the TDCC M = 12.50 value denotes the transducer must be positioned at a distance of 12.5 millimetres (0.49 in) from the breech face.

Some have incorrectly concluded that C.I.P. measures pressure at the case mouth to account for the variations from SAAMI pressure.

As transducer C.I.P. almost exclusively uses one type of Piezoelectric sensor (named "channel sensor") made by the Swiss company Kistler that requires drilling of the cartridge case before firing the proofing cartridge in a specially made test barrel. The Kistler ballistic pressure measurement sensor 6215 has a maximum working pressure of 600 MPa (87,023 psi) and is mounted recessed inside the cartridge case (the face of high-pressure sensor does not contact the cartridge case) and requires that the test cartridge case have a hole drilled in it prior to testing. The test cartridge must be inserted into the chamber in such a way that the hole in the test cartridge case lines up with a gas port hole that channels the gas pressure from the cartridge case to the face of the sensor. The measurement accuracy of the pressure measurements with 21st century high-pressure sensors is expected to be ≤ 2%.

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