If missed, it can be also acquired later in the same mission, next to the Comm Terminal just before going to the roof. The rifle is in a dead-end corridor, to the right of the elevator, when your back is against its door. The M-97 can be found during Thane's recruitment mission, near the service elevator that takes you to the bridge. While kinetic barriers still offer some protection from this weapon, its sheer power and rapid rate of fire make it capable of quickly killing almost any target, regardless of its defenses.
Rosenkov Materials developed this deadly weapon in response to the rising prevalence of kinetic barriers. Very effective against armor somewhat effective against shields and biotic barriers. Incredibly accurate and deadly at long range, these weapons are popular amongst infiltrators and assassins.
