Fracture

When you first get the ALM-37, the next area is littered with extra ammo should you run out. This is the best place to fulfill this achievement. Simply freeze an enemy (or multiple with this gun), run up, and melee him to shatter him to pieces. You need to do this for 25 kills.

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.

You can also do this in the weapons test, although you will need 80 data cells to unlock all weapons and 100 data cells to unlock the tdv in weapons test mode. All you need to do is equip the weapon and step on the red circle for a little and that will spawn enemies...freeze the enemies with the weapon, and then melee to kill...it will unlock after you get 25 kills.

Hi ignore the above - guides
LOAD UP - LEVEL - GENETIC RESEARCH BASE (casual)
Play through the level past the turret gun section-
past the bit where u destroy the battery things
- you will be directed to the ALM-37 (box on left -commucation center about 6 minutes into mission)
This weapon has 9 bullets - if u can try and get more than one enemy with it - once bullets are used -
load up checkpoint or die - rinse repeat.