K'Nex crossbowits got power, and range. i don't have averages yet but the last version shot 20 feet and has some power. this version has good power and can pierce cardboard with a good shot from app. 5 feet away. not bad.
the reason i am posting this is to show a new idea i had for removable parts. the only removable part i have for it right now is the head rest, but i am hoping for people to make other removable parts for it.
this gun has a ratchet system on it. so it can take a lot of power from rubber bands.
the gun also has a ammo holder that goes into your pocket. you can see a picture of me holding the crossbow with the ammo holder in my pocket(yes it is me(yes i blocked out everything else)).
it is pretty easy to make, so i made it with the metal K'Nex pieces because i though it would be cool.