According to SIG website (the way I read it) the P938 SAS model is a specially designed variation of the P938 line with fewer sharp edges, projections, etc, to make it a more enhanced concealed carry weapon. In the gun shop comparing the SAS, Blackwood and Extreme models, I don't see any physical differences. Aside from the color differences they all looked the same to me and the gun guy at the counter. What are we missing?
9x19mm--Anything bigger is statistically insignificant.