of course, that the pressure at the proofhouse. You should use light load, stay under the limit, you have an old gun, nobody have check your barrels...or the lugs...
I do not reload and have doseage for powder A1 and A2, it that means anything here, let me know.
Have the lenght of your chamber checked it is maybe longer than 65, a gunsmith may have worked on it before.
g

g gournet