Did you try a diferent lot number of primers? You may have a bad lot. Try a diferent brand of primers as well.
What you are reading about the primer cup being harder mostly deals with pistol primers. The CCI br2 primers are a benchrest primer, and have a soft cup. The CCI magnum primers have a harder cup.
When seating your primers are you seating them all the way down, against the anvil? If not the firing pin is spending some of its travel and momentum seating the primer. Are you unifrming, and cleaning out your primer pockets after each laoding?

What ever you do don't buy a heavier spring, the factory savage spring has plenty of power and is over kill for the application to start with, going to a heavier spring will only cause different problems. (Such as a heavier bolt lift, and possible harmonics applied, just to name 2.)