Darryl, I have tried 308 Lapua, 308 UBR small primers, 250 Savage and Norma 6XC cases, and a handful of Fed 22-250 cases, all made into 6-250 30° Imp. Of all of these, the Norma 6XC is the simpliest to form into my case. All of these except the 6XC require a shoulder push, even the 22-250 brass.
For the 308 brass, I used a friends 250 form dies 1, 2, and 3, (die 3 is an inside reamer die) then a shortened 308 die to set shoulder way back, then thru the 6-250 size die.
For the Norma 6XC, it's once over the 260 mandrel and thru the 6-250 size die.