I love the marketing ploy Sig used with the naming of the cartridge. They duped sooo many people (including Texas DPS). I have even heard Troopers call it their .357 Magnum Sig pistol.
Educate yourself about firearms before even handling one, much less buying one. To call it a .357 at all is a joke. The .357 Mag uses .358" diameter bullets. The Sig round uses .355 or .356" diameter bullets. .001 or .002 is a huge difference in ammunition.
Now that I think of it, I hope the original poster was joking.