Pump-action shotgun with large bullet spread, sharp falloff, and high damage output. Somewhat effective against ARC armor plating.
Headshots only
2 to break shield, 1 for health
No headshots, 100 shield + 100 HP
Remember that the 2x headshot multiplier does NOT apply to shields. Against shielded enemies, focus on breaking the shield first (body shots are equally effective), then switch to headshots to maximize damage to their health pool.