This is the 300 Torres, a necked down version of the 378 Weatherby magnum developed by italian custom gunsmith Celestino Torresani before the advent of the 30/378 Weatherby.
Note the shorter case lenght compared to the 30/378 WM. Looks like a fatter 300 Weatherby, with probably the same OAL. It is CIP listed.
Note also the proprietary hds, the original hds has been erased and the new one is really well made by Torresani himself.
Rare caliber so are the rifles so chambered. I have no idea how many of these cases have been made but I suspect production has been very limited.
From left: 30/378 Weath , 300 Torres, 300 Weath
Some dimensional data:
Rim: 14,62 mm
Belt: 15,38 mm
Base ( just above belt) : 14,77 mm
Shoulder: 14,23 mm
Neck: 8,50 mm
Body : 58,36 mm
Neck: 8,94 mm
Case: 70,94 mm