Special Forces IE "Green Berets" have some leeway in what they are able to carry. For the most part it is either the M9 or a Glock of some sort mission dependent. Carrying an M9 in Afghanistan is fine when you don't have to conceal it. However a Glock 19 is quite a bit easier to conceal if your mission requirements dictate that you be in civilian clothes quite a lot. SFOD-D from what I hear can carry pretty much anything they want to. They select the best weapons they can for the mission they are going to be doing. I have never heard however of anyone carrying the 357 sig. As I stated before I know some of the investigation detachments carry .40 S&W, and I believe the Coast Guard LE carry the SIG P229 in .40 also. I think that is the only non standard military round that anyone carries in the military.