There is a interlock that should only allow you to fire a nail when; 1. the trigger is pulled. AND, 2. the gun is in contact with the wood. Something is hung-up and binding. Go back through and check/lube/smooth the trigger mechanism and the contact at the tip of the gun. With most HF stuff, the finish can be bad. All it takes is some rough spot to bind and it does what you are seeing. That said I have a couple of HF nailers. Including a Framer, once I tuned it up, its been great for me. Good luck!