My 700 likes the white-box win too. I made a huge mistake when I first started reloading for 22-250. I thought that once fired shells didn't need to have the cases trimmed back. If you're doing the same consider yourself lucky to get 1.5" and lucky that you still have a gun in one piece. The 22-250 is generally a pretty darn forgiving reloaders cartridge so I don't know what it could be besides something in case prep. I still haven't had luck with 60gr partitions, but that's likely because I've only tried one powder and the partitions are probably just too long for my guns 1-14" twist. There are alot of more knowledgeable guys on here, they'll be able to point out other problem areas with the 22-250. Good luck