6.5x57 is standard for brass thickness, I think. There is no reason for it not to be.

Excellent round, BTW - if loaded to normal specs for the 57mm case. It's better balances, case capacity vs. bore size than the 6mm version - the 6MM Rem and therefore is very efficient.

SAAMI standard for the 6MM Rem is 65,000PSI. CIP for the 6.5x57 is 57,000PSI.