The new .255 GS ( Giani Special) has been developed by Vittorio Giani of MAG armi.
It is no more than the 6.5 x 55 Swedish Mauser necked down to .257" and slightly improved.
CIP approved , it is still a semi-wildcat, since no headstamped brass or loaded ammo is available.
Anyway, this will be available soon
Custom loads by MAG are loaded with 100 grains Barnes TSX bullets and develop about 3300 - 3500 ft/sec
Custom made rifles in this caliber are available from MAG armi as custom products