some data of my actual "device" -> Let me show you its features ! ;-) rubber powered (10 parallel theraband silver on each side) transmission ratio to bow string 1/4 push & pull energy storage frame material : Aluminium size: 80cm*20cm*20cm stroke length 55cm (pusch&pull) bolts: DIY 27.5g 10mm quadratic aluminium + steeltip magazine (up to 10bolts , so far only used 5 DIY) bolt velocity 70m/s bolt energy 70J efficieny about 50% (depending on temperature,...) overall weight 2,8Kg Backdraws of design (to be improved in next step): rubber tubes have bad efficiency at cold temperatures heavy rollers -> bad efficiency magazine not exchangeable trigger (aluminium) wears after several shots bolt holder broke at dry fire too much power -> how the hell do i get the bolts out of the 27mm doka plate ?? Questions: Did I post this in the correct category or would be "Slingshot Crossbow" the better channel ? Anybody working on similar targets ?