Yeah, you do need to declare your intended targets and intent to activate autofire before the attack. That is how the difficulty gets set
Apologies if I implied that this wasn't the case.
Firing off seven or Eight shots in a matter of seconds at multiple opponents, some falling behind cover, some soaking shots, some deflecting off armour, it would be hard to micro manage those shots so efficiently to say that my shooter could determine shot by shot if the targets were going out of the fight. For me asking the PC for targets ahead of time is a risk reward situation where he decides who the threats are and how long he pauses to spray them with laser before he twitches to the next target. I don't think this is unreasonable.
Totally. I agree that you should ask for targets ahead of time (when determining difficulty). If you're going to require him to state which shot goes where, though (during adjudicating Advantage, and before knowing who is down and who isn't), that's something that gets a little hairy by the rules so you'll probably want to have a discussion out-of-game to address how you're going to handle these situations going forward. In my experience, players generally respond favorably to this approach.
There's definitely some give and take required on both sides of the table. You sound like you've got a good handle on things, though, so my advice is just talk to your player and tell him how it's gonna be for the sake of everyone's enjoyment.
And...ah, I did not realize he jury-rigged it. I had assumed a really high Advantage roll. Doc, the Weasel's advice might be good for this situation (allow him to autofire ONCE for 1 Advantage, but subsequent activation on the same combat check require the normal 2 Advantage).
The Autofire rules were pretty heavily modified during the Beta test period, and still they can be broke-tastic ![]()