The answer is clearly that, on pressing the button, you experience walking out of the machine and being shot. Why is this clear? Because that's what you experience when you walk into the fake machine -- obviously, because it's fake. And if the fake and real machines can't be distinguished -- note that the real machine could, in effect, turn into the fake machine after you've pressed the button, for instance if the data transmission gets lost somewhere between Britain and Australia -- then your experiences of the two mustn't be distinct either. We know what you experience in the fake machine; we know that you experience the same thing in the real machine; therefore your experience of the real machine is pressing the button, then being shot.