sniper,even at lvl 13 i got a 4.3k ambush,and that's quite something.
That is because below 50 PVP all your skill and stats are scaled temporary to that of a 49 for the duration of the WZ. So by using that fact, what you should be saying is "I am hitting 4.3k Ambush at lvl 49"; which is quite pathetic, actually.
Sharpshooter spec Gunslingers is all about burst as all their core abilities triggers Trickshot 100% of the time and the buff last about 4.5 sec. This give GS a lot of freedom in how much they want to burst and when to do it.