If you had read into this species, it hiding all day wouldnt come as a shock.
Those that are forced to live in the open due to poor habitat tend to live short, stressed lives.
What horror stories have you heard about pistols?
Its only the very rare species that seem to be predatory, none of the pistols I have had pair with gobies have ever taken an active interest in snails or inverts.
They are about as loud as someone snapping their fingers...though size does affect the volume..moreso of the appendage itself than the shrimp.