Sizing problems are a result of the flash holes. Not only are the primers crimped/sealed but S&B and Ruag both use an undersized flash hole. So when sizing the case you are actually forcing your decapper to make a larger flash hole and the resistance is noticable. On a standard press with a short pin it will work with effort but be sure to clean out your primer cup afterwards as you may find burrs resulting from the pin pushing out a new size hole. They are a pain in the a$$ if you havnt experienced before, especially when the new hole pinches the decapper, requiring brute force and creative cursing to remove.
Cheers
dB