[MrForbes]

We are taking a different approach. As Gdeaver says, a mechanism that can store energy and quickly release is a dangerous thing, and we felt that relying on interlocks and safety procedures is not adequate. So, we designed our mechanism to behave like any other pneumatic actuated device when the ball is not loaded into it (ie. it moves slowly), and to act like a ball launcher only when the ball is in place.

I think it would be difficult to do this with any mechanism that uses springs.

And any mechanism that has a latch (or two or three or...) that suddenly releases a spring loaded bar is intrinsically dangerous.