Automatic Firing Nerf Gun Mod

Edit 1: I am currently working on a V2 of this design as it has a few flaws, especially with the wiring.
Edit 2: Version two has been temporarily delayed as I accidentally shorted my ultrasonic sensor.

Auto Firing Nerf Gun using the following:

-Arduino Uno R3
-HC-SR04 Ultrasonic Sensor
-SG90 Micro Servo
-Arduino 9V Battery Pack
-Nerf ELITE Disruptor
-Mini Breadboard

The thing files are the Trigger Cam which uses one of the servo actuators embedded in it, a modified Nerf sight rail to hold the circuit components (adapted from https://www.thingiverse.com/thing:3541911), and an Arduino and a mounting plate to hold the servo in place. Please note that we manually drilled holes to mount the servo to the plate and the plate to the Nerf Disruptor. All mounting was done using M2.5 6mm and 8mm screws.