Use it with the new Cerberus Vanguard, there's a small glitch which makes the class super powerful -
1) Start firing the Reegar at your target from a safe distance
2) While still holding RT, perform the Smash power at the same time by pressing LB
3) Even though it shows the Smash animation, it is also firing and reloading the Reegar for you
4) By the time the Smash animation has completed, your whole clip has been spent and reloaded.
Not sure if this works for all classes, but I do know it works for the new Vanguard with the Smash power.
Sweet! :lol
Thanks