This is my knex land mine that shoots out shrapnel when a trip wire is pulled. i decided to use the simple block trigger idea and make something creative instead of a gun (although you may consider this a gun, because it shoots knex pieces) any ways, you can use pretty much any knex grenade that fits itself together loosely, like mine(you just have to put a white rod on it).
This is the Firing mechanism that makes the grenade explode. since the bullet doesnt go all the way in the barrel, it smacks it and makes the grenade blow up. Make sure to tape the firing pin. adjust the rubber bands so that if you pull it back, put it at a 45 degree angle, load in a white rod, and shoot it, it should go 15 to 20 feet. here i used 3 thin rubber bands.
ROCKBAND RULES!!!=
:Dcool idea though.