Fracture

All of the weapon specific kill achievements can be obtained in the Weapon Training mode provided you have unlocked them by collecting the Data Cells.

The Dragon's Breath is the machine gun turret. Score 25 kills with this weapon to unlock the achievement.

Note: Gun kills apparently stack even after death or loading from a checkpoint. If you find a good point in which you are killing many enemies with this gun and you've just saved, press start and select "Load Last Checkpoint" (or whatever it is). You'll reload from the last checkpoint but the game's internal counter doesn't. Thus, the amount of kills you had with this gun prior to your reload will not return to the point of that save.

On Chapter 2 Right after you pick up the Freeze Gun you will go up a Elevator you will come to a open Space where you are Getting shot by a Turret This is a Great place to work on this all you gotta do is rush the Turret and use your Freeze gun punch the frozen guy and hop on the turret and you can get about 20 kills just don't kill the last guy let him kill you rinse and Repeat till it pops. Also a Great place to get the Freeze Achievement for 25 kills with the ALM-37. So you can Get both achievements right here hope this helps someone