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Within firearms, chamber pressure is the pressure exerted by a cartridge case's outside walls on the inside of a firearm's chamber when the cartridge is fired. The SI unit for chamber pressure is the megapascal (MPa), while the American SAAMI uses the pound per square inch (psi, symbol lbf/in 2) and the European CIP uses bar (1 bar is equal to 0.1 MPa).
A low cost method of gathering pressure data uses a resistive stress gauge attached to the exterior of the chamber. These systems are usually calibrated to emulate the results of an existing standardized system such as the SAAMI system, so that the results will be directly comparable.
While CUP and LUP numbers were intended to be comparable to the crushing power of a given pressure, the numbers are not equivalent. Since a longer duration, lower pressure pulse can crush the cylinder as much as a shorter duration, higher pressure pulse, CUP and LUP pressures frequently register lower than actual peak pressures (as measured by a transducer) by up to 20 %.
Pressure recorded in NATO design EPVAT Barrel with Kistler 6215 Transducer, HPI GP6 Transducer or by equipment to C.I.P. requirements 9 mm (9×19mm NATO) Designed to chamber NATO ammunition: 252.0 / (36,550) 315.0 / (45,687) Pressure recorded in C.I.P. design barrel at mid-case position 12.7 mm (12.7×99mm NATO) Designed to chamber NATO ammunition
In C.I.P.-regulated countries, every rifle cartridge combo has to be proofed at 125% of this maximum C.I.P. pressure to certify for sale to consumers. This means that .308 Winchester chambered arms in C.I.P.-regulated countries are currently (2008) proof tested at 519.00 MPa (75,275 psi) PE piezo pressure.
Operating chamber pressure of the Springfield model 1873, firing the 45–70–400, is 19,000 psi. [4] The operating chamber pressure of the Springfield Model 1884, firing the 45–70–500, is 25,000 psi. [3] According to the US Army Ordnance Department tests, the 45-70-405 was loaded to 19,000 psi, [4] while the 45-70-500 was loaded to 25,000 ...
.223 Remington – Original AR-15 cartridge: .223 cartridges may function in a 5.56×45mm rifle, however 5.56×45mm cartridges may produce excessive pressure in a .223 Rem rifle. On the other hand, a .223 Wylde chamber is used on .223 Rem rifle barrels to allow them to safely fire either .223 Remington or 5.56×45mm NATO ammunition. [6]
A barrel chamber with pressure relief ports that allows gas to leak around the cartridge during extraction. Basically, the opposite of a fluted chamber, as it is intended for the cartridge to stick to the chamber wall making a slight delay of extraction. This requires a welded-on sleeve with an annular groove to contain the pressure. [8]