The British Ton = 2240 lbs, so 3 Tons = 6,720 lbs. As Larry said though the gun was proofed to a higher pressure & certified as proofed for 3 Ton pressure loads. The 3 ton reference was also a crusher pressure measurement & not the later PSI as obtained by use of Pieso-Electic crystals which will show a higher pressure than the crusher readings.
Incorrect.....
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One (1) British long ton axial CUP = 2638 PSI..CIP radial PSI....
British pressures are HIGHER than they seem, i.e. 1 long ton is only 2240 lbs, but one long ton PSI is 2638 PSI.....
The conversion of an axial base measurement to the equivalent radial measurement:
Conversion of radial crusher (CUP) to radial transducer (psi) measurement is well approximated by the following relation: psi = 9e-6 *CUP^2 + 0.7051 * CUP.
Otherwise expressed as 9 times 10 to the -6 power times CUP. This conversion works well for most modern values of European and American pressure in firearms.....
Also note:
For the modern Piezo equipment ....1 British long ton = 2850 Piezo PSI.....
Therefore THREE (3) Long Tons would be 8550 PSI as measured by the modern Piezo equipment.....
http://en.wikipedia.org/wiki/Piezoelectricityhttp://en.wikipedia.org/wiki/Commission_Internationale_Permanente_pour_l%27Epreuve_des_Armes_%C3%A0_Feu_Portatives
http://en.wikipedia.org/wiki/Birmingham_Proof_House