Surplus ammo is regularly posted in the "Shotgun News"
I would not rebarrel or rechamber it though,
the 7.65 is one of the best designed of the Mauser cartridges.
it is only slightly less powerful than the 30-06 in military
configuration. it is slightly more powerful than the 308
due to a larger case capacity. Usable cases can be made
from 30-06 Or any of the "Long" cartridges the '06'
was the parent of. The Belgians used the 7.65x53 also,
but the cases are a bit different when measured.