For what its worth.
I dry fire the shit outta my guns, both real and Airsoft. I dry fire my shit thousands of times more than I shoot them. ( the exeption being rim fires and free float pin shotguns and transfer bar single actions.) my back up S&W revolver has less than 100 rounds through it but I have probably dry fired it with and without snap caps over 10,000 times. How do you think I keep a double action on target the first shot so well, and how do you think the action got so smooth?
Anyway, I have owned tm and western arms m9's and dry fired them thousands of times. I do proper maintenance on my gear.
I have been gunsmithing for close to 25 years and airsmihing for close to 10 years. I have fixed so many 14 year olds upsidedown up shit that it's not even funny. I have never seen any failure that can be contributed to dry firing ( exept rimfires and floated pin shotguns)
You upsidedown your shit up dude, be a man and take responsibility. You opened it up to see how it worked and failed to reassemble properly.
Problem solved, one loose screw behind the trigger.