Hm...real fast? If you´re sculpting them yourself I guess fast isn´t part of that deal. The only option I see is buying an airsoft version and making casts of it. But that would be recasting?!
And from there on, you´d still have to have a vacuum table to form abs, or molds you could make resin copies from.
I really don´t know for sure, but if you don´t have the tools there probably isn´t a fast way to make a lot of them.
Maybe a props company would lend out some too you?