Purchase a conformal piezoelectric pressure transducer from a supplier like Kistler (model 6215 or 6239 for rifle chambers). Calibrate it according to the procedures in AEP-97. Use the reference pressures listed in SAAMI or C.I.P. (for 5.56mm NATO, maximum average pressure is 430 MPa or 62,366 psi).
The standard is mandatory for:
Describes the use of NATO’s EPVAT (Electronic Pressure, Velocity, and Action Time) system. It mandates the placement of a conformal transducer 25 mm from the breech face for rifle cartridges. Maximum allowable mean pressures are given for each caliber. stanag 4157 pdf
Measure velocity 15 m from the muzzle. Calculate the standard deviation. For NATO acceptance, a standard deviation of velocity ≤ 4 m/s (12 ft/s) is typical. Measure mean radius at 100 m. For 5.56mm ball ammunition, mean radius should be ≤ 40 mm (1.5 MOA).
Tables of Acceptable Quality Levels (AQLs) for critical, major, and minor defects. For example, a pierced primer is a critical defect (AQL 0.1%), while a cosmetic scratch is minor (AQL 4.0%). (for 5
Standardizes the “mean radius” method rather than extreme spread. The test target distance varies: 100 m for rifles, 50 m for submachine guns, 25 m for pistols. The standard defines the maximum allowable mean radius in milliradians.
Do not despair. The technical content of STANAG 4157 is mirrored—sometimes verbatim—in national and international standards that are openly available for purchase. These are your best resources: Maximum allowable mean pressures are given for each caliber
The document typically contains an alphabetical listing of abbreviations. For each entry, it provides: