According to the 2.1.1 patch notes, at the beginning of 3v3 (or 2v2 for Crimson Doubles at least) no one is supposed to have special weapon until the first ammo boxes spawn. After some experimentation (for the sake of curiosity) a friend of mine I was playing with at the time discovered that if someone begins the match with a Sidearm equipped which always spawns with ammo, then switches to another special weapon after the match begins, they will have some (albeit not much due to the switch penalty) ammo for whatever their selected weapon is. This would immediately grant that player a massive advantage against the enemy team by allowing the immediate use of, say, a Shotgun without any wait time. The match after he confirmed his theory, two players utilized a variation of this loophole to bring Sniper Rifles into Round 2 of Crimson Doubles after we stopped them before the boxes spawned in Round 1, the variation just involving waiting until the span between Rounds 1 and 2 to change weapons to possibly reduce the ammo penalty for switching weapons.