re: What about the rifles?
Are you sure those weren't US sniper rifles, the big .50 caliber jobbies? Those are turning up in insurgent hands too; some may have been captured from US soldiers, or ripped off from depots, or even bought in the US (yes, they could, until recently, be purchased legitimately from gun stores). I'm not saying the Iranians are blameless, I just think there are other possibilities.