[stlmia]

No. The larger barrel wont fit into the smaller slide. But smaller barrels WILL fit into larger slides. Whether or not you SHOULD shoot it that way is a different question....

 

[Trophied]

40 and 357 Sig are interchangeable with just a barrel swap, but the recoil spring and barrel diameter on the 9 are both different from the other two calibers. At least per a conversation with a Sig person.