The M-170 Hammer first appears in the level: The Last Stand. It is very powerful and can kill a human mutant with direct hits from as few as two shells. Under normal conditions, it fires a single shell per shot, and is semi-automatic , but the Hammer's alternate firing method launches two shells at once, which requires handlign it as a Pump-action Shotgun . It appears to be similar to a SPAS-12 in design and function, and thus it is likely based off of it. The M-170 normally appears to use Gas-Operated Reloading , but when using it's alternate fire is pump-action. The reasoning for this is unclear.