The ONLY reason I opted for a Lyman mould for this caliber (#266469) was the rifle's very catholic throat and groove specs--Ruger 77R with 6-groove .256" x .264", throat about .2645." .265" Buckshot H&I die and all goes well to 1900 FPS. If another 6.5 x 55 comes along--esp. a milsurp--I would have one of the semi-custom makers or SAECO do the work.