This I know for sure
A case fired in a Bar-Sto before sizing will fit in a sig chamber but a case fired in a sig chamber will not fit in a Bar-Sto chamber before sizing. That tells me the Bar-Sto is a tighter chamber. I called Bar-Sto today and they said yes there barrel does have more chamber support.
It is a non issue to you but have you blow an extractor with a sig barrel. A tighter chamber will give more support and work the brass less. Sure I could back the load down but the Bar-Sto handles it with no problems. The sizing die works the brass very little because the chamber is so tight. So you see I answered my own question with a call to Bar-Sto this mourning,
Thanks,Keith