Thread: over-pressured brass

Recently I bought few bertram brasses (6.5 saum) and noticed they are very soft, to the point I have to decrease my load by 2-3 grains, comparing to the load I normally use with norma brass.
I noticed once the brass is over-pressured there is no use to anneal it, it is always hard to load a projectile. I ended using my expender die to "soften" the neck. But still, the accuracy is always bad, I mean from 1/2 to 2 inches. Has anyone know/read why it could cause the accuracy to drop? Elasticity?