I was having a similar problem on my only rifle with .223 Wylde chamber. All of my reloads looked good in a Dillon case gauge. In practice and general shooting, it seldom happened because I wasn't ejecting a live round. But, it was happening on every stage of a recent match. I checked with factory rounds, and they ran fine. After some reading here, I reset my sizing die by turning it down about a full turn. I now have no more problems with my reloads.