This is our custom designed release pin. It goes on the tip of the arm. Using this and a turnbuckle (which can be picked up at any hardware store) you can make small adjustaments to the trajectory of your projectile. We have used this to launch baseballs all the way to launching 10 lb. watermelons 1,000 ft. It's made out of 3/8" steel and is guaranteed not to break.
$25 + shipping