The springfields that I have seen that have factory ramped barrels are using the Wilson/Nowlin ramp. To tell the difference, remove the barrel and look at the area just ahead of the ramp. If it is cut square, it is the Wilson/Nowlin style, and if it has a semicircular extension it is the Clark/para style. They both work equally well, but the W/N is a little more difficult to machine the frame for.