This is an improved trigger to get a more positive release from the mini Crossbow http://www.thingiverse.com/thing:509659.

Note: Use a small drill to clean out the trigger hole so that a piece of 1.75mm PLA just fits through the hole. Use a little heat on one end of the PLA to form a head that looks like a rivet. Push the other end through the Crossbow, through the trigger and out the other side. Cut the PLA so that 1/8"-3/16" sticks though the other side. Carefully heat the end and form it like a rivet.

I think you will like this trigger