I believe,however,that some of the above listed calibers can ba eliminated from consideration.The 6.5x65R is too recent to be considered.The 6.5x70R is a very slim (about 25-20 head dia.)cartridge used in small,light guns,and this BF has a 16 ga barrel next to the rifle barrel;the dimensions just do not demand such a slim caliber.
At a glance it looks to be aforementioned 6.5X70R or 6.5X70R Nimrod. I have a surplus of boat-tail grackles and crows from this a.m., so Ford, do you want me drop the black-bird pie off at your house??? Wait till after the 1st & I can mix in some squirrel to make it more palatable.
With the 7.76mm measurement, I wonder how the tilde factors in to the proof equation?
Kind Regards,
Raimey
rse