According to QL the 7*65r brennecke has a max pressure of 55114 psi, the 7*57r has a max pressure of 49313 psi. If it`s a bad choiche for a break open combination gun I don`t know, but most drillings in Norway are 6,5*55 or 308 win (yes idiotic cartridges for a break open gun) and the pressure in those are 55114 psi for the 6,5*55 and for the 308 win 60191 psi.