Not sure if there is a way to consistently make it happen, but many times as I was playing Gunner I would go to slam, it being either level 1,2 or 3, and the game would freeze as the gun hit the ground, not sure if this is some glitch in the code, also just as a request, would you please put gunner back to the way it was before the update? It is too frustrating to time reloads and try to avoid being hit (which is made even worse by the reloading update as it does not allow against close range defenses with grappling and slamming), and this is a imperative thing since gunners are usually on the front, and need to be constantly spitting out bullets.
How 'bout they just give him a bottomless clip. Oooh, and make him as fast as the Assassin! Oh! how about he starts with juice! Yeah, the Gunner would be truly badass!