[Twicepop]

It doesn't appear to be your gun or reloading procedures causing the problem. Winchester brass has had some poor quality issues from time to time. Several of the vendors at the gun show I attend no longer have or will sell Winchester brass anymore. They've changed either something in the brass formulation or their quality controll standards, heat treating would be my guess. Now I have to ask, are they buying it from a Chinese source?

those who beat their guns into plowshares, will plow for those who didn't