The issue of operating pressures – for example of the 5.56 NATO and .223 Remington calibers – opens a controversial scenario, often the subject of debate among enthusiasts. So let’s analyze the differences between Cip and Saami
Exactly comparing the operating pressures of American and European ammunition is not always possible. A possible parallelism with the measurement methodology specifically adopted by NATO on military cartridges complicates the issue even more. The European Cip (Permanent International Commission for the Test of Portable Firearms) uses the piezoelectric transducer system with probe positioned – roughly – in the middle part of the cartridge. To carry out the survey, the case is drilled so that the expanding gases, upon combustion, can directly interact with the sensor. Differently, the American standard Saami (Sporting arms and ammunition manufacturers ’institute) does not provide for any modification of the cartridge case but keeps the position of the sensor unchanged. The operating pressures that will be obtained will therefore not be superimposable to those found in the old continent, as the verification technique is clearly different from the Cip system, which, with the same ammunition, will detect higher values. Further are the US military systems. The Epvat (Electronic pressure, velocity and action time), used by NATO to test the pressures of the gauges intended for small arms (5.56 × 45, 7.62 × 51, 9 × 19), positions the transducer at the height of the collar of the cartridge case. The Scatp method (Small caliber ammunition test procedures), used by the United States Army, imitates the Saami system. The hardness of the brass and zinc alloy that makes up the case, and its thickness, will directly affect the expansion capacity, thus interacting with the measurement. Reason why, the Cip specifications are among the most reliable.
Cip and Saami for the .223 Remington
Returning to the .223 Remington caliber, the Cip provides an average maximum P of 4,300 bars, equal to 62,366 psi (pounds per square inch, or pounds per square inch). The Saami standard sets the average pressure limit of the .223 Remington caliber at 55,000 psi, corresponding to 3,792 bar. Considering that ammunition tested in the USA are sold in Europe and vice versa, by passing the conformity checks in both cases, a likely uniformity between the respective values can be assumed. Different systems of relief can only offer different operating pressures while analyzing the same ammunition by caliber and type.