You can't figure the tons by multiplying x 2,000 or even 2,200. It is indeed a service pressure rather than a proof pressure. Ithaca1 has the 850 bar proof pressure correct, converted to psi as measured with a transducer. (If you multiply x 14.5, you get LUP rather than psi, because those bar numbers are lead crusher.) Service pressure for an 850 bar gun is 10,730 psi as measured by a transducer. That's straight from the Birmingham Proofhouse.