These are real numbers from my brass and another members brass. His chamber is already opened up. Mine are saami from Proof and xcaliber.You wont get that much sizing. The brass does not come out of the die the same size as the die. If it did all of this would be really easy and I wouldnt have to go through the trial and error process. If your reducing the base .003" currently then your fine. Most likely the chamber is already oversized if thats happening.