The 6.8 SPC? I suspect the real issue would be if the die is too long to get the 6.8 case far enough in to work the collet. I love the Lee Collet Neck dies but they just don't make it for the 6.8. May have to neck size the old fashion way.

Contact Lee. They make custom dies for not much money. My brother had them make up a die for 25-35, the Factory Crimp die I believe it was. If it's a matter of simply cutting down something common like a 270 then it should be fairly easy for them to do. It wouldn't hurt to ask.

I found the good folks at Lee to be wonderful to work with and would not hesitate recommend them to anyone needing a die. Contact them and I'm sure that they will do well for you.