I've heard that it can be done, but not vice versa. Also I don't know what's involved. The outside of the slide is somewhat thicker that the SR9c. But it's the inside dimensions that matter.
I've got both. I might try putting my SR9c barrel in my SR40c. But I doubt it will fit without some sort of modification. Possibly the whole slide might work on the other frame. Dunno. Good question!