Answer:
Don't spin the barrel.
Step-by-step explanation:
Each time you spin the barrel, the probability A of finding a bullet, having two bullets in six chambers is:
For you to get shot in the second try but not the first, the barrel spin would have to stop precisely at one specific chamber: the one right before the bullets, so that probability would be:
which means that this event is half as likely as finding a bullet every time the barrel is spun. Your chances are better if you pull the trigger for the second time without spinning the barrel.