one thing i learnt very quickly. When charging, make sure you plug the charging plug in at the wall first making sure the switch is turned off at the wall, then plug the charging end into the gun, then go back to the wall and switch on the power.
Any other variation can make the circuit screw up and even fire off a round.
You can adjust the trigger, but try getting used to it, you accuracy will be so good once your used to it.