I'm so glad this thread is here.
Winslow throws epic tantrums once or twice a day and I can do nothing but put him in timeout. That's where the task lies though, as he flops onto his back snapping at whatever he can get. It is not fun or easy to deal with (i actually do wonder if this is cause for concern), and I hope you get through this stage with Butter earlier than we're dealing with.. he's coming to 7 months now.
Keep at it, he will get it!