[Lawpass]

For sure use the kingman 9.6v battery.
You can try dialing the velocity all the way out (decrease velocity), if the battery is weak for some reason, decreasing the force caused by the spring will give it a better chance of being able to trip the sear and let you know if its a battery problem. If its not a battery problem, then its probably something on the board and you should give Kingman a call. Hope this helps.