Object.shootVelocity
Type: Number
Default value: 2000
Overview

The velocity with which the object will produce a shot (rate of fire). The property object.allowShoot should be set to true.
Examples

local newAI = require('classes.SimpleAI').newAI
-- enemy instance
local enemy = newAI({group = mainGroup, img = "snailWalk1.png", x = halfW-50, y = display.contentHeight-500, ai_type = "guard"}) 
enemy.allowShoot = true -- the object now will fire periodically
enemy.shootVelocity = 1000 -- the object will fire once in second