That wasn't the short answer, or at least I hope it wasn't
, but you are doing what I suspected. You are eliminating the small amount of case stretch by making the secondary shoulder. And I can see that if you don't know how long a chamber is, your approach is technically better. On the other hand, Wyoredman's chamber is a known quantity and fireforming a case in his chamber (or mine) shouldn't be that risky a business and quite honestly should not need the extremes that you suggest. If, however, you are changing calibers and it isn't something simple, like 223 to 223AI, your approach is understandable.
And now I do understand what you were saying. Thanks.