According to another Forum that is dedicated to the Sig pistols it is entirely possible with just the change of a barrel, they recommend the Bar-Sto 9mm "conversion" barrel. Make sure to get the "conversion" barrel and not the "replacement" 9mm barrel. It is supposedly a drop in part, some say that you may need to smoothen some areas in order for it to be a true "drop-in". You may go down in caliber, but not the other way due to the pressure differences involved. Go to the Bar-Sto website for their recommendations. The cost was around $200 to $250 and there apparently is a wait for their barrels. There are other manufacturers that are also supplying similar items but the concensus among the Sig shooters leans towards Bar-Sto. Hope that this helps you.
