With the 35 Whelen, if the cases are sized correctly for the chamber, then you will not have issues with headspace or light primer strikes. The thing is, the same is true of ALL cartridges. If the rifle's chamber is longish, you might have to back the sizing die out a bit for a good fit in the chamber, but again, nothing different than 30-06 or any other bottleneck round. Poor reloading technique can screw-up any loaded round, even the 35 Whelen.
