Someone noticed this problem and turned it into a money making attachment for semi-auto guns. I looked and I see Cabala's sells these add on stocks.
It all works on the same principal described in this thread; a certain type trigger finger and recoil will cause a double to take place.
Watch this happen:
http://www.youtube.com/watch?v=ks5id...id=P8yZQ3EHk5g