You do need to activate the swinger, even if it's after you're done shooting because according to 9.9.3, "Moving scoring targets will always incur failure to shoot at and miss penalties if a competitor fails to activate the mechanism which initiates the target movement."
I'm not saying this necessarily makes sense...but that's how I'm reading 9.9.3...
Not so fast. How could you activate it after you are done shooting? Once the command "range is clear" is given, that is the end of the course of fire (8.3.8). Now if you walked back to the activator prior to that, I can understand. That implies you safely retreated to that point, at which time you might have surprised yer RO.