I have a 223 Rem 700 that often (30%) fails to eject the case, it just falls onto the follower. I have taken the bolt apart and cleaned it , including removing the plunger and spring both of which seem OK with the same strength of spring as on my other 700's . The ejector is also even with the top of the bolt head. I replaced the extractor a while ago which helped but did not cure the problem ( the extractor is the newer one without the rivet). Any ideas as to the cause?