While CUP and LUP numbers were intended to be comparable to the crushing power of a given pressure in psi, 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%. For example, the SAAMI maximum pressure for the 7.62 x 51 mm is given as 52000 (CUP), or 62000 psi (430 MPa); the .45-70, on the other extreme, is listed as 28000 in both CUP and psi (190 MPa). SAAMI standards for a given cartridge may be expressed in CUP units, LUP units, or in standard units of pressure (psi or MPa).
So there is No exact formula for cross refencing CUP to PSI....
__________________
[I]You know you might be facing your doom,when all you get is a click when you're expecting a BOOM!:( [/I]
Last edited by Mooseman684; 11-10-2009 at 03:16 PM.
So it would be like comparing Rockwell harness to Brinell(not sure if I got the name right)hardness. both measure the same thing but in diferent way's and wth diferent scales.
Travis
A copper crusher, a copper slug and a pressure barrel is used, and once fired, the copper slug is removed and measured and compared to a documented scale to get CUP.
A pressure gauge, and pressure barrel is used and a direct reading is taken.
.308 was rated at 52000CUP and is now 62000PSI (?) (I don't remember the exact number, it could be 6500PSI). Just comare the 46th Edition of the Lyman manual to the 49th Edition.
