you have the normal cocking based crossbow, but in addition to that, you also have the option of switching to automatic mode.

In this mode, the crossbow is either cocked via the piston, or is propelled by it, depending on what would give out the most velocity for the simplest design. It would also on the piston down stroke, load the next arrow to be fired.

While it would create a bit more sound and requires fuel to operate, you gain increased responsiveness. Though at the same time, engineered properly, even that will not make too much sound.

Useful for lazy hunters, and also some special operations guys with a death wish.

----

I still would recommend on looking into electrical means of propulsion, if only for managing sound emission. Or maybe even clockwork?
-- mofosyne, Aug 15 2010

Hilti Gas Powered Nail Gun http://www.hilti.co...ng=en&nodeId=-17503
Think of it as a crossbow with REALLY short bolts. [MisterQED, Aug 18 2010]

Arrow shaped ammunition http://en.wikipedia...c_energy_penetrator
[goldbb, Aug 18 2010]

A bolt propelled by a piston using stored chemical energy for lazy hunters? I'm sure I heard of that somewhere.. can't place it...
-- Voice, Aug 15 2010


I sketched something like this up one time when I found out that arrows go through Kevlar and sand bags I wondered why the millitary wasn't using auto crossbows, but I can't find the doodles.

I figured that the arrows could feed up through the bow's stock from a belt system. A timed conveyor along the top of the stock track would draw the bow.
It should also be possible to fire five or more bolts simultaneously, if they emerge from below into half-tubes which are slotted for the course of the bowstring, and set the desired spread of the bolts for a given range.

If mounted on the back of a jeep or personal transport, a PTO from the engine would provide the power for full auto.

I had gone as far as to design specialty bolts for the thing but I'm not really into the whole death and mayhem thing so I let it go.

(+) for reminding me of that.
-- 2 fries shy of a happy meal, Aug 15 2010


//petrol powered guns// the 14:1 stochiometric mixture whomps not bangs: the bullet would get stuck in the barrel... would work with smoothbore and a quarrel.
-- FlyingToaster, Aug 18 2010


//it does tend to beg the question of why there aren't petrol powered guns around// But there are, from Hilti. (link)
-- MisterQED, Aug 18 2010



random, halfbakery