Design and Specifications
The large capacity of the .500 Express case is due to the cartridge originally being designed to use black powder as a propellant. The 3.00 in (76 mm) case has a case capacity of 138 grains of H2O (8.96 cm3) while the 3.25 in (83 mm) case has a capacity of 158 grains of H2O (10.30 cm3).
The CIP regulates the 3.00 in (76 mm) version of the cartridge but not the 3.25 in (83 mm) version.
The CIP recommends 7 groove barrel with a twist rate of 1:15. The barrel is to have a groove Ø of 13.00 mm (0.512 in) and a bore Ø of 12.70 mm (0.500 in) with a groove width of 3.61 mm (0.142 in). Maximum average peak pressure for the cartridge is 2,800 bar (41,000 psi) for the 3.00 in (76 mm) version of the cartridge. While the CIP does not regulate the 3.25 in (83 mm) version of this cartridge this cartridge is loaded to a lower pressure of 2,700 bar (39,000 psi). Except for length and overall length, the 3.25 in (83 mm) version of the has the similar dimensions as the 3.00 in (76 mm) case.
Read more about this topic: .500 Nitro Express
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