How do you know that is what happened? I have used the Sinclair sizing oil for resizing and used a ultra sonic vibrator with the recommended solution to take it off, but the first 10 minutes of solution did NOT take off the oil. I should have run the brass through clean water and then done it again for 10 minutes. I was test firing after the first batch and I noticed cratering of the primers... even before the power got too strong. I'm thinking this might have been some of the oil was still on the cases. I hope you experienced guys will let me know. thanks