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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 complicating matter regarding bolt thrust is that a cartridge case expands and deforms under high pressure and starts to "stick" to the chamber. This "friction-effect" can be accounted for with finite elements calculations on a computer, but it is a lot of specialized work and generally not worth the trouble. [2]
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 %.
The case of a converging-diverging nozzle allows a supersonic flow to occur, providing the receiver pressure is sufficiently low. This is shown in figure 3 assuming a constant reservoir pressure with a decreasing receiver pressure. If the receiver pressure is equal to the reservoir pressure, no flow occurs, represented by curve A.
With high-powered cartridges, a significant amount of force is required to engrave the bullet which can raise the pressure in the chamber above the maximum design pressure. Higher-powered rifles usually have a longer freebore so that the bullet is allowed to gain some momentum, allowing the and the chamber pressure to drop slightly before the ...
Pressure inside reactor for the synthesis of high-pressure polyethylene (HPPE) [76] 250 MPa 36,000 psi Record diesel engine common rail fuel system pressure [77] 400 MPa 58,000 psi Chamber pressure of late 1910s .50 Browning machine gun discharge [citation needed] 240–620 MPa 35,000–90,000 psi Water pressure used in a water jet cutter [78 ...
In rockets, due to atmospheric effects, the specific impulse varies with altitude, reaching a maximum in a vacuum. This is because the exhaust velocity isn't simply a function of the chamber pressure, but is a function of the difference between the interior and exterior of the combustion chamber. Values are usually given for operation at sea ...
Characteristic velocity or , or C-star is a measure of the combustion performance of a rocket engine independent of nozzle performance, and is used to compare different propellants and propulsion systems. c* should not be confused with c, which is the effective exhaust velocity related to the specific impulse by: =.