My Speer #11 manual says that 22 gr of that powder is the max load, so if you are using thick brass it could cause a pressure build up. Also, maybe a silly thing to say, but if your case length is too long and hitting the rifleing this would also cause major pressure build ups. If your bullet is on the lands, it will cause a slight pressure build up too. But generally speaking, if you are experiencing loose primer pockets after a couple loadings, you are shooting a hot load for your rifle.
Good luck, Mark
I used to re-load but now I "hand-load".
-- Well, at least I try