When I was into making my own bullets a few years back, I tested a lot of commercial bullets too, including the smk. I found that they would not expand reliably, as you have indicated. The Berger's we're always better. Since they both have hollow points and very thin jackets (around 014" for the Berger and some Sierra jackets were you only .012") I always believed that the big difference was the nose angle. At the time, the Berger's were a secant ogive and the Sierras a tangent. I .E . More pressure "outward" on the Berger meplat. When I tipped Sierra jackets while making my own bullet, they worked great,! Now that Sierra is using a more aggressive nose, that may have changed, BUT, they now do an extra crimp to close the meplat, so I doubt that they are likely to open either?? ......rich