M-300 Claymore Heavy Shotgun

A very rare krogan shotgun. Deals high damage at short range; less effective at long range. Effective against armor, shields and biotic barriers. It is of human design but is only used by krogan, due to the fact that the kickback from a single shot is enough to break a human's arm. Protected by Fabrication Rights Management (FRM) technology, this weapon is nearly impossible to reproduce and is prohibitively expensive.

Acquiring
After recruiting Grunt, asking him about upgrades will have him show you the M-300. Originally, Grunt is the only character who can use it. However, it can used by Shepard if you choose it as advanced training when the option arises (this will also give you the weapon if you had not built it yet). It has the lowest clip size of any shotgun, firing only a single shot before the thermal clip has to be ejected.