Daryl, the 6.5 x 47 Lap case is similar to a .250 Savage case (necked up) but far more robust, to cope with the higher pressures!
Doh! Homer
.250Sav. or .22/250 - 1.914" - same case - I would use the .22/250 case necked up - thinner necks perhaps? - you guys are aware, I suspect, that even though it has a LOT of taper, the standard .22/250 case is a 65,000 SAAMI PSI cartridge.